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Our "old reliable", test mule & continuing work-in-progress...

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 Not too promising at first glance...cannibalized for miscellaneous parts, rusty and non-running. We figured that the engine was a goner, good for a few spare parts at best and that the bike was an oddball rolling chassis,  suitable for a custom build. Closer inspection revealed that, non-obtainable parts aside, this was one unusual bike. ST70's weren't equipped with engine/sparkplug guards, high-mounted fenders and hydraulic forks in 1972.  European-spec ST models didn't get oil-damped forks until 1980 and they never had the CT70 K1 gatorless type; this bike not only had these items, but still had 1972 Oregon registration decals...civilian and military.  All of the text on the various frame decals was in Japanese. We suspect that a US serviceman purchased this bike in Japan circa early 1972 and imported it to the USA courtesy of Uncle Sam. During the teardown, we discovered that we had gotten an unexpected bargain. The frame was straight, except for a couple of superficial dents, the wheels were straight, the chrome was not pitted even the engine and sparkplug guard were salvageable. What appeared to be major rust turned out to be surface rust. The motor had been freshly bored, honed & fitted with a new piston and rings...someone had jammed the cam chain tensioner during reassembly. This caused the cam chain idler to seize and the teeth were stripped when the engine was kicked over. What looked like a lump of coal, turned out to be a diamond in the rough.

 

 

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Same bike, different day... Here it is three weeks later,  with a new Chinese Zongshen 110cc motor, 22mm carb...topped off with a K&N filter, free flowing "stealth" exhaust (if you look closely, you can see that the outlet is nearly twice the size of original), aftermarket adjustable shocks and an 80mph speedo. Since one headlight mount was missing, we decided to fabricate a new set from scratch rather than try to locate a salvageable original. We were never that fond of the exposed spot welds of the originals anyway, so the handmade replacements were leaded-in for a smooth appearance. The length was set to accommodate the K0 headlight shell with the K1 forks. The lower fork tube covers were painted in the same Chroma red 2-stage urethane paint, to match the bike, then mothballed in favor of the more durable K2-`79 fork gators. We treated the original sparkplug guard to a bit of metalworking, then sent it out for rechroming. The engine guard and tail light were simply reused as-is. The Japanese writing on the tail light bracket decal is the sole reminder of this bike's history, a touch of patina on an otherwise fresh build. While the bike may be rare, there was little chance of getting all of the missing parts and probably less chance of documentation.   Japanese domestic market (JDM) bikes are extremely rare outside Japan and it is virtually impossible finding comprehensive model information on them. Thus it was decided to build a roadworthy bike using the best OE parts regardless of model year as well as the best the aftermarket had to offer at the time. The end result was a bike that rode and ran far better than it had originally, even with two adult-sized passengers aboard, yet still retained a mostly stock appearance, right down to the modified exhaust and Bridgestone Trailwing tires.

 

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2004...after many months of research, we decided to try one of the new generation Honda engines, a 110 Nice. These motors had been getting rave reviews and while the Chinese 110 had performed well for us, it never quite lived up to expectations, being short on power and a bit "rough around the edges". From the first mile, the new motor showed it's true colors. There was no mistaking Honda quality and refinement. The tranny was smooth and quiet, even with less than a mile on the clock, something it's predecessor had never been. The Chinese engine had the advantage of a cam upgrade & big valve head and seemed a bit revvier but, in reality, this engine only gave up nothing. It is a lot torquier, with an amazingly broad powerband and just seems to pull itself along smoothly and effortlessly from  just off-idle to redline. After a thorough break-in period, we were happily surprised to find that the bike picked up about 7mph in top speed and could now cruise  at 55mph. We had sought refinement and got it, plus the power level we had wanted from the first engine.

As you would expect,  some minor modifications were required. The footrest assembly was spaced to allow adequate clearance for the heel/toe shifter and the exhaust interfered with the oil filler. We carefully heated and re-bent the exhaust and cut down the upper mount. The pipe now allowed the use of a dipstick thermometer (to monitor oil temperature) and gave the passenger a break from getting a roasted right leg at stops. The overall angle looked better, too. We weren't too thrilled by the as-cast appearance of the cam cover and black powdercoated engine side covers, so we polished the LH cover and cam cover. We left the RH cover as-is...for the time being. 

The end result of this phase of our ongoing project is a bike that has "real bike" operating characteristics and can easily keep up with traffic. The bike will cruise along at 50-55mph, even when riding two-up, with ease and the miles pass by quickly. Top speed is around 65mph. Frankly, we seldom thrash the bike for top speed runs these days. Practically speaking, the tires and stock brakes are limiting factors. True, dual-purpose capabilities require knobby tires. While the OEM Trailwings are the best available, the tread design is far from optimal for pavement. It's a very good dual purpose tire, but you can hear the tread howling/whining at speed and the 62mph speed rating dovetails nicely with the speed at which the feeling of stability quickly fades. As the tread wears down, stability improves but leaning into corners at peg-scraping angles is foolhardy without dedicated road tires. On those rare occasions when we go for a bonzai blast, we're noting that the bike keeps getting faster...icing on the cake.  We just enjoy it as we had originally intended, as a reliable & fun machine. Engine power, gearing, tires, riding conditions (including posted speed limits)  are all best suited to sustained speeds below 60mph.  If your goal is a reliable, OEM-like machine, this setup is an excellent first level upgrade. It is, perhaps, the bike Honda might have built if the CT70 were introduced today. The look, sound and overall feel are pure OEM Honda. It's easy to keep in tune, requiring nothing more than seasonal low-speed carb adjustments between the hottest & coolest riding weather. Engine performance is what you'd expect of a Honda; one-kick starting, smooth from idle-through-redline, with a usable powerband over most of the same range, and the clutch/trans so smooth that seamless closed-throttle upshifts have become second-nature. In fact, being able to seamlessly granny-shift a bike this small is a hoot. The alternator produces enough current to allow a real headlight, making night riding possible. The bike has never broken down and has been ridden as far as 70 miles away from "home base" carrying nothing more than the OEM toolkit ,  a spare master link (neither of which has ever been used), and extra fuel. We've also ridden into areas of nothing but logging roads, with the nearest phone 15 miles away (and no cell towers in the area) with full confidence and no disappointments. In terms of what constitutes OEM reliability, being able to simply jump on and ride wherever you want to go without fear of being stranded on the roadside is the acid test. So far, 4000 miles and still passing with flying colors.

3-mile cruise, riding two-up...here

 

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2005...With the engine fully broken-in and tuned to a razor's edge, we turned our attention to front-end upgrades. The fork legs and disc brake setup from a fullsize Honda were adapted to fit. Most disc brake conversions require the use of aftermarket wheels, front and rear, adding hundreds of dollars to the final cost and changing the look of the bike even further from original. The OE wheel and hub combo are fairly versatile and  just look "right" on these bikes; retaining them also allows retention of the original speedometer drive with minimal modifications. We worked with a local machine shop and used this project to prototype the pieces and required mods. A quick trip to a metal supplier, an afternoon's fabrication & polishing turned a piece of scrap T6 6061 aircraft aluminum into our new adjustable headlight mounts. The final pieces of this puzzle are the alloy upper and lower fork trees; a stainless steel retaining nut was custom made and we installed a tapered roller bearing headset as well. Minor mods were required to mount the master cylinder. The new fork shocks are a good match for the weight of the bike, a bit better than stock K1-`79 and give a quiet, well-controlled,  slightly firmer, ride quality. The front caliper is a twin-piston unit and the newfound stopping power is fade free and nothing short of awesome. The bike can now be yanked to a stop from 60mph with authority.  Overenthusiastic application of the front brake could easily put the rider over the handlebars! So there you have it... a classic Honda Minitrail from the early `70s, updated with a balance of modern power,  brakes, suspension, lighting and speedometer to match. Best of all, the updates were realized using genuine Honda parts,  without breaking the bank or losing the classic lines of the original bike.

From this point we feel that the bike wants for very little in the way of additional improvements. It is now a competent and reliable road machine, able to handle 50-55mph traffic with relative ease, even riding two-up; it seems just as happy covering our favorite logging roads in the wilds of Michigan's upper peninsula. And, of course, just as importantly, is still easily transported in a hatchback car or minivan. It's that combination of portability/diminuitive size, 2 passenger capability, on/off road competence, and OEM reliability that set this machine apart from other bikes. We can't think of another that's as versatile. Thus, there are only a few very minor refinements planned ... but then you never know!

 

A Bump In The Road (Literally & figuratively)

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June 6th, 2006

A perfect summer day, sunny & 85 degrees. After the unusually cool weather of April and May, we were anxious to get out and catch some sun & breeze. What better midpoint than a tongue-in-cheek attraction... Hell, Michigan, on the one day this century with a date of 6-6-06. This normally quiet, idyliic, setting along the Hell Creek located amidst the Pinckney State Recreation area was packed to the gills with a couple thousand day-tourists, mostly bikers. The first 110 miles of our 120-mile sojourn went along uneventfully, as planned... an hour and fifteen minutes out, the same back with an hour's stopover in the middle. Unfortunately, the return trip would provide a nasty surprise. About 10 miles from home, we hit an unexpectedly rough railroad crossing at 50mph. This had happened many times before without incident, thus what happened next was quite a surprise. A loud cracking noise was heard and the bike suddenly felt loose. We quickly pulled off the road in an attempt to figure out what had happened and discovered nothing out of place. Heading back out onto the road, the bike still felt odd, yet a second going-over revealed nothing more than the first. It wasn't until we returned home that we discovered what had happened; the RH upper shock mount had snapped cleanly at the shoulder. Since the outer stud/nut was intact, everything appeared to be intact & in place, held together by the muffler mount. The Kitaco shocks were so stiff that the LH shock alone was enough to allow the bike to be ridden with only a vague sense that something was wrong. (The spring preload was on the softest setting!). Giving the devil his due? Hardly. Remember that RH shock mount was bent when we received the frame. We had our doubts about its condition, even after it was straightened. But, after survivng 4000+ miles, some of which had been riding two-up over trails, with no signs of imminent failure, we hadn't expected this.

Fortunately, nothing else was damaged. The remaining mounts (frame & swingarm) were all perfectly straight, even the single shock absorber was intact. The first thought was to thread the outside of the remaining stub and machine an adapter, similar in design to the stud/nut used to mount the muffler to the shock mount, only larger and of stronger steel. Unfortunately, the shock mount axle is not a standard size, nor is it uniformly round.  Thinning the center section would weaken its structural strength. The original shock mount was DOA.^(

Since this frame was solid, straight and free of rust...not to mention titled, insured & registered, we didn't want to scrap it. Sometimes when life hands out a lemon, it really is possible to make lemonade (or, perhaps more accurately, "chicken salad from...chickens**t"). Here was an opportunity to overcome a problem that has spelled "the end" for many a CT70 and make the bike better than new in the process. We had to  rescue our faithful workhorse from the glue factory...and begin what would be its transformation into the ultimate dual-purpose machine. You didn't really think we could leave "well enough" alone did you? Our motto is " when somethng fails, replace it with something better. While the bike was completely torn down, to be rebuilt from scratch, we weren't starting from scratch this time.

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LEFT: Initially, it appeared that we could simply use a fine-thread die to cut threads into the outside of shock mount axle stub. Those traces of paint & primer were a worriesome sign, but the non-threaded area at the upper left meant that the mount axle was not perfectly concentric. Since the threads that were cut were marginal, at best, with minimal depth, this repair was not viable and major surgery would be required...shit!!!  RIGHT: Since any proper repair would involve welding, it was decided to replace the original mount entirely. Being dedicated to ongoing improvements  ("if something breaks, replace it with something better"), in this instance, that meant having a new center section precision machined from steel twice the diameter of the original, the use of grade 12.9 bolts the diameter of the original center section, and adding bracing plates to the outside of the originals. The weak point is now the bolt, which can be easily replaced. Aside from not wanting to repeat this repair, the viability of doing so is questionable. Plus, that would mean stripping & painting...yet again (ugh). This is why we shifted the breaking point from the mount itself to the bolt. Realisitcally, the possibility of the bolts breaking is remote. If one were really worried, it'd be easy enough to carry a couple of spares and an Allen wrench. The center section is as large as we could go without making wholesale changes to the frame (more cutting, bracing & welding). Rockwell testing showed that the bolts are far stronger than even the thick center section of the OE mount.

 

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This kind of frame surgery isn't for the inexperienced, or the faint of heart. But it's the only way to replace the shock mount axle. It's interesting to note that the metal is about .1875" thick at this point. Honda was years ahead of the rest in applying unibody technology to bike design.

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Left: New mount center section in place for mock-up. No, we're not inventing the new CT70 dice game, those are the spots where the new outer bracing plate will be plug welded. As can be seen, the metal was quite thin at the bottom of the frame sidewalls after removal of the factory shock mount. While the most of the strength comes from the material above the mount, it is always best to distribute loads over as large an area as possible when dealing with this type of frame construction. The principle is the same as installing a roll cage in a race car. Below: After a quick trip through the blast cabinet, the new .1875" thick sideplates were plug welded to the originals and metalfinished. Note the added material at the bottom.

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On the road again...

Unless the seat is raised, the repair is barely visible. Unfortunately, the paint suffered third degree burns and some serious paintwork lies ahead.  Once refinished, the repair won't be noticeable at all unless the seat is raised and there's no worry about breaking another upper shock mount. In the unlikely even it were to happen, the wheel would probably be damaged from the severe impact required. Replacing the upper shock mount bolt would be the easy part. This is our second skunkworks project...the CT70 upper shock mount repair kit.

IMPORTANT NOTE: While we feel that the upper shock mounts are weak points of the CT70 basic frame design, we don't believe that they are exceptionally prone to breakage. The frames that we've received with bent shock mounts have all shown evidence of abuse, such as stunt jumping. As can be seen in the first photo of the shop bike, it only had the RH shock when we got it. Considering the neglect & parts cannibalization the bike had endured, it's not much of a stretch to imagine some numbnuts riding it minus the LH shock. Weak shocks can be even tougher on the bike's structure than overly stiff shocks. They'll bottom-out easily and once that happens, there's a solid mechanical link between the road and the frame. It's a bit like hitting the shock mounts with a sledgehammer. Stock shocks are pitifully weak and bottom-out easily under adult weight; a single shock would be like no shock absorber at all. The cause of our broken mount: microscopic cracks on the underside of the mounting stud, at the shoulder point. Over time, these created a stress riser, where the metal snapped after becoming work-fatigued.

 We replaced the noisy & rock-hard Kitaco shocks with top-of-the-line, high-pressure gas-filled, shocks with piggyback reservoirs, from our our own line of high-quality shocks . The improvement in ride quality is unbelievable, even when riding two-up. The damping chracteristics are a quantum leap beyond the old Kitaco pogo sticks. And unlike the Kitacos, they're quiet. The bike has seen about 500 miles with this setup in place, 150 of which was done riding two-up (320lbs of combined passenger load) over nearly every kind of road condition imaginable, including dirt roads and railroad crossings. The range of spring preload adjustment is more than adequate for anything we'll ever need without the harshness of overly stiff springs. We'd guess that the bike could carry as much as 350 lbs, but that's just an educated guess based on our experience. 

 

What's Old is New Again... Rebirth of the Shop Bike

With the end of riding season close at hand, we decided to move forward with the complete teardown and refinishing. We have some big surprises in the works and, paintwork aside, winter is the best time to tackle major projects.

 

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What was "good enough" when we started out years ago just won't cut it anymore. Once a new finish is applied, you quickly forget about the warts beneath its surface. After stripping the frame back to bare metal, we repaired some "rediscovered" dents using body lead instead of plastic filler as had been done last time. We also smoothed-out the chain damage and rough welds on the swingarm. This time around, the shop bike gets true candy ruby red and the frame, though mostly stock in terms of metal finishing, will have the crisp appearance of a freshly pressed $2000 suit.

 

 

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The Shop Bike - version 3.0

Over the past six years, we've used and at times abused the shop bike. It's served as guinea pig, lab rat and even crash test dummy for a number projects; perhaps your engine was road-tested and/or broken-in fitted into this bike's motor mounts. This latest project began with a huge head start, courtesy of our long-suffering machine. The tradition continues on as, rising yet again, Phoenix-like, from it's own burnt wreckage, "Old Reliable" comes back for the latest round of innovations, with some great surprises along the way.

First order of business was a complete repaint in true "Candy Ruby Red", the last paint job of the 2006 season. Previously we used DuPont Chroma red, a "near candy". While a decent simulation of candy red and  very simple to apply, there's just no substitute for true candy colors. Though it's only necesary to wait a couple of weeks before applying decals and such,  we wanted the luxury of completing the bike slowly during the off-season, giving the paint months to fully harden. Unfortunately, between multiple engineering challenges, supplier and chrome plating delays plus a heavier-than-expected springtime schedule, we were unable to complete this project until late July. We should have known better with a custom project; Murphy was an optimist!

We've never been afraid to discard our own work in favor of something better.  Thus, we  painted two headlight shells, a K0 and a 12V type, the stock swingarm and chainguard, knowing full well that there would be "spare parts" at the end of the build. The later-style headlight shell is an inch larger in diameter, which makes for better lighting with the Nice alternator and 4x OEM capacity battery we've fitted. In the end, we used the larger headlight, as expected. It is a tight fit, especially with the billet mounts which we hand-fabbed. The chainguard and swingarm also ended-up in the spare parts bin. We chose to retain the engine-mounted chainguard, making the OEM unit redundant. Also changed, at the 11th hour was the swingarm. While the stocker is a plenty stout piece, likely tougher than our aftermarket alloy replacement, it's not without its shortcomings. The rubber pivot bushings work well enough, and we've seen few that have failed, but...they do bind a little at the extremes and our biggest gripe is the fact that there's no good way of preventing chain contact from chipping the paint on the LH side. The chain adjusters also rip through the paint at the axle flanges. Thus we jumped at the chance to test out a new-design, triple-wall, aluminum swingarm with ball bearing pivots. It comes standard  with a nylon/delrin chain pad which absorbs any chain contact and the chain tension adjusting system doesn't chew-up the axle flanges. Losing some unsprung weight didn't hurt anything either; there's been a noticeable improvement in the rear suspension action. We also added a subframe brace for added frame strength and rigidity.

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The front end presented a number of engineering challenges. First off, it was decided to stick with the OEM Honda disc brake we've been using. This is the same twin-piston caliper/220mm disc setup found on some larger (and much faster) bikes such as the NSR - "if it ain't broke..." That left only a few thousandths of "wiggle room"; brakes being a high-precision item. We've also received a number of requests for a setup that would allow fitment of a 3.50" wheel as is possible at the the rear, which, hitherto, has never been possible with off-the-shelf parts.  Further, when adding power to these bikes, it can be desireable to extend the wheelbase and shift the weight bias forward. This improves high-speed stability and makes the bike less wheelstand-happy. There's also the issue of suspension action. The K1-`79 front end is surprisingly good, for what it is, and can be tuned somewhat through the addition of heavier springs and oil. However,  it still only has about 2.5 inches of travel. The Honda Nice fork we had fitted previously was a little better than stock and, of course, gave a greatly improved brake setup; it still had less than 3 inches of excursion and the springs were a tad on the soft side for offroad use. We knew going in that this would be neither cheap nor simple. With the beleaguered greenback falling to new lows against most major currencies, imported parts (virtually everything on a Japanese bike), stainless steel, have all taken major hits; aluminum, especially the high-strength alloys we use, has become astronomically expensive. Furthermore, we used USA talent to handle the design, engineering and CNC chores. This time, it was absolutely a no-compromise approach with everything subordinated to function.  Extended-length swingarms work well; added wheelbase smoothes the ride and adds straight-line stability at speed. The trouble is...we don't like them aesthetically. The CT70 frame is a stylistic element in its own right and going more than +2cm on a swingarm makes the rear tire appear disconnected from the rest of the bike. Extending the wheelbase from the front end, is an approach we've not seen applied to these bikes. Considering the difficulties involved, that's no surprise. The effects are similar to fitting a longer-than-stock swingarm, but the wheelbase extension can be less for the same amount of effect, making it almost undetectable. Widening the spacing not only allows a wider-than-stock wheel/tire combo, with anything near stock width, the front wheel can be removed without unbolting the front caliper. The fork legs we selected have almost 5.5" of total travel, real internal valving and readily available preload adjusters. They also seem to have variable rate springs, not an advantage from what we were told going in. Thus, custom springs and valving were planned. We did consider fitting an OEM CT70 hub, however, they aren't as straight & true as we'd like for a top-of-the-line front end. We normally have the lateral runout corrected on a lathe when machining them for disc brake conversion, but nothing can be done for radial runout and stock speedos can sometimes leave a bit to be desired. Thus we went with billet disc brake hubs and G-Craft CT70 wheel stars to retain the stock lines with perfectly true-running wheels.

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Off-the-shelf headlight mounts are available and would have been a lot easier. With as much tweakage invested in a project as there is in this one, you had to know we couldn't leave well enough alone. We fabbed a simpler version of the billet mounts used on the custom special; they complimented the polished trees and aluminum swingarm. We also fabbed a custom footrest unit, mounting the footpegs higher than original for added ground clearance. This is a benefit both on road, where peg-scraping leans can be hazardous in tight cornering and for offroading, too. A custom battery carrier was fabbed as well. The new, larger capacity 12v sealed batteries available are physically larger than anything used in these bikes "back in the day", but they do fit in the stock location with a wider-than-stock carrier and careful placement. That's a serious consideration for a clean underseat area and to provide room to mount the voltage regulator or CDI. When we first built the shop bike, we had no source for OEM Dax decals; we are now able to source a pair that were the same as the 35 year old OEM JDM set the bike came with. The only difference is that these have yellow lettering instead of orange. We also decided to move the horn to the RH side using an engine guard bolt rather than drilling and tapping a hole into the lower tree. The low-mount, late model ST70 fender was retained, though the mounts proved cumbersome due to the relatively heavy fender. The high-mount CT70 front could have easily been fitted and does look better. Remember, this is an exercise in pure functionality. Things have to look good, but only in ways that do not detract from function. The low mount fender does a far better job of keeping crap off the engine and lower surfaces of the bike. Dirt/gravrel roads in this part of the world are treated with calcium chloride to control dust. Calcium chloride is, in reality, salt and is murder on steel, aluminum and chrome. With a mudflap fitted for offroading, the bike should remain nearly spatter-free, with zero reaching the engine itself.

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The last few details were just that, finsihing details. Some of them were a bit over-the-top (we've become polished aluminum addicts), but, if you consider the reality of them, they're mostly more practical than intuition would indicate. The RH engine case was polished. We grew tired of the rough-ish black factory powdercoat and it was pretty well scarred from multiple engine R&Rs. Fact is, it doesn't take much to maintain polished aluminum. Engine parts get hot and that slows oxidation. Two or three sessions a year with Mothers mag & aluminum polish or Neverdull and paste wax should do it and the shiny surface won't chip off. We added a red-anodized outer clutch cover (purely decorative) that looks pretty cool with the polished cover peaking through from below. The red color goes well with the bike and the rising sun motif seems fitting for a bike of Japanese origin. We also polished the stator cover plugs for the flywheel while we were at it. Pretty much everything else was reused as-is. The rear shocks were fine, as were the rack, seat, tank & bracket, oil cooler, carb, handlebar assembly, rear fender and tail light assembly. Even the chain and sprockets, after 4500 miles, were like-new. We ran the chain thtough the parts washer, then lubed it with molten paraffin. We did replace our 5-year-old Trailwings. With roughly 5000 miles of mostly road riding, they were a bit "tired". Amazingly, the rear brake setup was still like new. The clearcoat has kept the polished aluminum backing plate looking the same as it did years ago and there's less than 25% wear on the brake shoes. It was still amazing how much work was required to free the rear tire from the split rim. Even without rust, it bonded quite convincingly to the rim. The wheel paint is still like new.  The old air filter was swapped-out in favor of a new-type UNI airfilter. It's an ugly thing, but especially well-suited for dusty conditions. The capper was the prototype of our upcoming "super stealth" exhuast. The aim was to see how quiet we could make the exhaust at speed, while retaining a nice, healthy-but-mellow thump at idle without a power decrease or an exhuast note with the dreaded "wet fart" character.

The finishing touches...

The bike went together with lots of surprises along the way. Funny how seemingly minor changes result in cascading alterations, but that's life. The front fender mountings took some .625" 6061 aluminum bracing to locate that heavy front fender solidly and both tire and fork clearance are incredibly tight. All stainless hardware was used instead of the original  bits. The bike is now so far removed from stock, that there was no point in retaining the stock plated steel pieces. Another longtime provider of show-quality chrome plating passed away during the build process. We'll miss him and there's not likely to be anyone stepping into his shoes. (Hey, we said there were numerous complications this year) This prompted our decision to change the design of the subframe brace and  likely discontinuation one version. There were a couple of machining issues and way more fabrication to deal with than anticipated along the way. It took two full days of metal fab & polishing. Just about the time we resigned ourselves to dragging every single detail of this build, kicking & screaming to completion, it was ready to roll. That's where things changed in a big way...for the better.

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Having been out-of-the-saddle for 10 months we figured that it would take lots of road miles to get everything tweaked and even more time to cover enough miles to figure out how much difference our changes had made. This was one time when we were thrilled to be wrong. The bike fired on the first kick and ten minutes later was rolling down the street. It took less than 500 feet to tell the difference,  no exaggeration. The ride is Lexus-like, plush yet controlled. The bike is smooth as silk for its size and the suspension soaks up everything the pitiful roads around here have to offer. We now have to be careful over railroad crossings, as they're hardly felt. Previously, the suspension would bottom-out unless we slowed considerably. With the preload adjustment exactly in the middle, the bike only uses about half of its fork travel most of the time, even with 320lbs or rider & passenger aboard. That's about the full range of the stock fork. The last 2-1/2 inches are still there, just waiting for something outrageous. We hope to never hit anything that hard, it'd be one helluva pothole!! The difference in ride quality is accompanied by improved weight distribution and stability, as expected. Even with the front end ride height set about .500" higher than stock and our rear shocks about .750" shorter than the first aftermarket pair (making them about the same as OEM stock), turn-in is noticeably better than ever.  Even the erstwhile Kitaco 350mm units weren't as good, the one area in which they excelled. Front end height is infinitley adjustable, we sneaked-in the extra height for added ground clearance...and got away with it. The bike is now so smooth and stable that it just begs to be ridden more miles. Spousal approval is now "two thumbs-up". First day out saw 135 miles and nobody was saddle fatigued, neither rider nor passenger. It only took 4 days to cover 567 miles. If there's a downside, it's that all of this newfound comfort & stability has decreased the sensation of speed; the super stealth exhaust adds to this effect. We hadn't considered this possibility. Whether it's good or bad is up to the individual rider. We are, as yet, undecided. The suspension is so good that we'd never go back...ever. However, a little bit of exhaust snarl might be more satisfying, at least part of the time. For that reason we are, for the moment, considering an adjustable baffle for this newest exhaust.

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Notes on the Super Stealth exhaust...

Our original Stealth Exhaust system has been a huge hit. Stock appearance, free flow and a note that's "just right" is a tough act to follow. There are, however, certain circumstances and individual preferences to consider. On long rides and in wilderness areas, even a moderate performance sound can be distracting. According to standard wisdom, sound equals power. We fully expected to lose a couple mph of top speed. That's no big deal for a road cruiser. Top speed is limited by gearing as much as anything, so our top speed won't go much beyond 65mph even downhill with a tailwind; the engine will run out of revs. The goal was a mellow tone at idle and under power and quiet part-throttle cruising. Putting years of experience and theory into practice, we have developed a clean-slate baffling system for this skunkworks project. At idle, the note is deeper, with more heft, yet 3-5db quieter. At WOT, that character changes a bit. At lower revs, below 6500rpm, induction noise is equal too, or exceeds, exhaust noise. Above 7000rpm, the exhaust note overshadows induction sounds with the same mellow roundness as at idle. At part-throttle cruising, you move along almost silently along flat roads. Using a dead-accurate speedometer in back-to-back testing, the results held some surprises. The bike seems a tiny bit slower with the quiet muffler. In reality, it's faster. Top speed testing would have been pointless. We're gearing-limited and there's way too much traffic locally to find out the absolute limits. However, there are some decent hills in the immediate area and hill climbing ability is very relevant; that's an indication of real world roadworthiness. We also have a few tightly defined "test tracks" short stretches of road where you must brake at the same place, or earlier, to avoid disaster (so no "cheating"). Where we saw 53-57mph with the original exhaust, we saw 56-61mph with the super stealth. All tests were repeated with multiple "ride it like you stole it" blasts all carried out within 90 minutes over exactly the same locations. Theory worked as applied. The performacne gains are subtle  going by seat-of-the-pants feel. The new exhaust is labor-intensive to produce, so early adopters may snag a bargain.

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There were three issues left to resolve...appropriate sidebages, final configuration of the front fender mounts and the speedometer. The fender mounts, as they are, didn't cover the exposed inner fork legs and were on the ugly side. We thought about replacing them with square billet, but lack of clearance limited structural strenght.  High-mount fenders are a non-issue; simply drilling and tapping three holes and making a spacer... and it's done. We fabbed a pair of deflectors/guards from 6061 and added them to the existing mounts.  The speedometer was more of a challenge. There is no aftermarket drive that is correctly calibrated an OEM Honda speedometer and 4.00 x 10 tires. We found this out thr hard way. The speed readings feel about right but are actually slow. Ego aside, that's not a good thing. At first we wondered why the bike was so sluggish at speed, that is, until we noticed that traffic had become uncharateristically slow on every local road. In our locale, speed limits are taken as suggested minimums.  Luckily, we checked the speed with radar and a pace vehicle without any speeding tickets. The solution  was a hard choice. An OEM hub conversion just didin't fit with this project. A shorter tire, such as a road tire used on a 12V ST70 would probably lessen the error considerably. That's not viable on a true dual-purpose bike. A second set of rims & tires doesn't really fit the "get on & ride" goal either. As the Trailwings wear down, speed readouts will gradually gain about 5-6%, who wants to wait until the tires are ready for replacement?  The only other choice was a user-programable electronic unit. We selected a unit that we could fit inside the speedo/headlight bucket. Not our first choice, but it preserved the stock-ish lines of the bike, is dead-on accurate and we gained trip meter and timer functions. We had planned on using an OEM 60mph Honda speedo with integral trip meter. Oh well, can't have everything. That's it, the bike is now done. There's nothing else left to upgrade or changeout.

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Conclusion

It's taken a lot of time, experimentation and resources but we ultimately achieved our longtime goals:

  • Adequate power to keep pace with traffic, no less than 45-50 mph on a 10% grade while riding two-up and 50-55mph steady-state cruising on relatively flat roads.
  • OEM Honda reliability
  • Smooth-shifting transmission and strong clutch.
  • 12 volt electrics with enough output for decent lighting.
  • Enough braking power to yank the bike down from 60mph at the limits of tire adhesion even with 300lbs of rider & passenger aboard.
  • Competent, adjustable, no excuses, suspension for comfortable riding with the ability to transition from road riding to offroading and back seamlessly.
  • Retention of the essence of the original bike: folding bars, mostly stock lines and ease of transport in a car/small van/SUV.

That's a tall order and from the outset, many have told us it wasn't possible; yet, in the end, we actually succeeded beyond our own high expectations, something that has rarely happens. We feel that the shop bike represents the ultimate dual-purpose-cruiser CT70. It has enough power to competently move along at any legal speed at which it can be ridden, even with up to 320lbs of combined rider/passenger weight aboard, with brakes and suspension to match. While the low-mounted front fender isn't our first choice in terms of aesthetics, it's clearly superior functionally. In addition to being much more effective at keeping things clean, the added airflow through the oil cooler is a welcome improvement. At speed, the airflow coming off the cooler feels like a car heater set to "max". We gave the bike its "trial by fire" on a 95-degree day. Riding two-up and at sustained speeds in excess of 50-55mph uphill and into strong headwinds, the oil temp topped out at 107C. That was after 25 miles, with roughly 10 miles of wide open throttle. On the return trip, oil temperature never exceeded 95C. 700 miles later, we backed this up with a second test that completed the circle. With our Copper Harbor trip out of reach for yet another year,^( we took a 120-mile day trip ...where else?...straight to Hell (MI). That's where this last stage of upgrades began and where our vacation travel plans went (wry chuckle). The bike, at least, came back intact. Ambient air temps were in the high 90s, with strong, gusty, headwinds on the outbound leg of the ride. With 335lbs of rider, passenger & gear aboard, at least 40 miles was covered at, or near, wide open throttle. Again, oil temp topped-out at 111C (about 230F) demonstrating not only the toughness of the Honda motor and perfect state of tune, but the sizing & placement of the oil cooler as well. This time, we saw peak readings of 103C on the return trip, on one prolonged uphill section. Some of the grades encountered, in combination with the strong headwinds limited top speed to 50mph. That's as hard as the bike can be pushed; with 9,000 trouble-free miles under its belt, we consider the Honda Nice engine virtually bulletproof. The stock lower end has proven reliable with up to 160cc over the past six years with nothing more than the addition of heavy-duty clutch springs. In stock form, the engine is pretty well unstressed even at wide open throttle; that's really at the heart of the reliability/durability issue. The bike has the kind of "set it & forget it" reliability and OEM-like balance we always wanted.  The ride is more akin to that of a full sized 125cc bike. We chose to forego adding extra power or road tires in favor of a ride-it-anywhere, run-forever setup. The ride is amazingly plush, requiring no compromises.  Slap-on a pair of road tires and the bike would be ready for some very spirited workouts through the twisties; it'd also gain a few mph on the top end. Add some more power and a steering damper and you'd have the upcoming silver bullet. That's amazing versatility...going from relatively tame to insane with a change of tires, engine and addition of one component. What's more surprising is that we're talking about a 1960s-era design, old enough to be exempt from most restrictive regulations, that's still not dated after four decades. A classic that we just made even better, realizing its full potential.

There is one last installment planned for this series, appropriate sidebadges. Those may be another skunkworks item. With the number of Nice conversions now out there, it's time to offer these for that final grace note.

This bike has taken a lot of torture and, we feel, has earned respect. We're going to put LOTS of miles on her and enjoy them all. We'll see how long we can maintain the current condition with proper maintenance. That's it, we have our "ultimate CT70 the way Honda should have built it" and it's a great little "vest pocket" touring machine. Any further changes would be guilding the lily. That doesn't mean that there are no other directions to pursue, we'll just do that with other bike projects. The Shop Bike has reached it's ultimate conclusion. We know only too well that nothing stays the same. However, for the intents and purposes of this, specific, project a new state-of-the-art has been acheived.

Thanks for following along. We sincerely hope that you've enjoyed this saga and that the CT70 community, in general, will benefit from our developments. We'll happily supply virtually anything you've seen here.

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