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 Read on and find out why we consider the Honda Nice the best motor ever made for these bikes and why we refer to it as...

 

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"The Rolls Royce of small bike engines".

 

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The clutch & transmission are the heart of any small bike engine. They are the main interface between bike and rider and are what you will live with every moment you're on the bike. They also determine how much power & rpm can be put through the motor assembly.

Vintage 4-speed transmissions are getting rarer by the day and replacement gears are all but impossible to find. Chinese trannies have proven notoriously fragile; most exhibit poor shift quality and are noisy. Replacement parts aren't even an afterthought. Japanese aftermarket clutch & transmissions come in 3,4,5 & even 6-speed flavors, but they can cost as much as  new engine and the 5 & 6 gear units have very narrow gears that don't stand up to big torque.

The stock Nice trans is the strongest unit we know of, needs no modification and parts are readily available. It's full ball bearing, too

Compare gear assemblies from a CT70H (top) to the Nice (bottom).

On the left, the countershaft third gear from the old design CT70/Z50/CRF trans. On the right, the same gear from the Nice. What's not shown is that the Nice gear transmits engine power through four drive dogs (located on the next gear), instead of two. Note also that the Nice gear teeth are not only wider and more finely-machined, the teeth are beveled for improved shifting. The cumulative effect of numerous, subtle, touches such as these is an engine of Honda quality and durability. These are some of the refinements that are lacking in Chinese copy engines. What's not obvious are the differences in metallurgy. Quality, high-strength alloys & finish machining add to the production costs of an engine.Of course, for the end user, these are precisely the things that pay you back... in value, if not outright dollar-for-dollar cost over the long haul.

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 On the left, the shift fork assembly from the Nice; to the right from a standard 72cc Honda. Note the large, hardened, contact blocks on the Nice forks. These are in addition to the fork tips and more than double the hardened  contact area. We've yet to see a worn-out shift fork from a Nice tranny. 

 Here is a disassembled Nice oil pump, oil spinner (centrifugal oil filter) and oil screen. The pump gerotor assembly is approximately four times the size of the units found in CT70/Z50/CRF engines - even larger than the ones sold as "300% oil pumps" and more than up to the task of keeping even 175cc tuned versions properly oiled. Note the comparatively huge oil passages in the pump body itself; it takes some serious oil flow to keep those passages filled. Better still, the pump is driven directly from the crankshaft. With no pump drive shaft competing with the crankshaft for space, strokes beyond even 62mm are possible with this engine. Also note the large, dedicated oil spinner. Since the clutch is located on the transmission mainshaft, a much larger centrifugal oil filter, with an optimized internal design that really holds particulates, can be used. Clean, high-volume oil flow equals long engine life.

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 Note the 4-plate clutch. The spring-damped basket is identical to the type used in many current-model fullsize bike engines. This setup has proven bulletproof even with 20hp+ tunes, with little more than the addition of heavy duty friction springs. Honda has used two designs, the older type has 3 pairs of damping springs, the newer uses a single H.D. pair and a larger throwout bearing. This clutch is used in a number of current production, new-gen, engines. The cheap copy engines we've seen use solid, non-damped, clutch baskets; drop the clutch on a hard downshift & all the shock goes into your tranny! That's less than optimal for gear & basket life. 

 A cool engine is a happy (and long-lived) engine. Compare the size & total area of cooling fins compared to the stock CT/XR/CRF70 design.

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Along with its 12V electrics & CDI, the Nice comes with a real alternator, more than capable of powering real lights. For the road rider, having a proper headlight and the added visibility it provides is more than a bonus.

 

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Chinese 110 vs. Honda Nice 110  road test details: ct110 - 3.png

  • Zongshen 110 motor, secondary clutch model with big valve head, fast road cam, 22mm carb, K&N air filter, Stealth exhaust. Ambient air temperature 68F, calm wind. Engine and gearing combination was thoroughly tested and optimized. Top speed observed on this test run was 55mph, on the downhill section. With 775 miles on the clock, the bike would consistently reach 57mph on the flat.
  • Nice 110 motor, 100% factory stock. 22mm carb, K&N air filter and same exhaust used with the Z110.  Ambient air temperature 85F, with a mild headwind. Top speed observed on this test run was 63mph on the uphill section of the exact same section of road. Unlike the previous test run, the throttle was not opened until  midway through fourth gear.  Not wanting to push a fresh engine to its limits, we initially backed-off the throttle once into fourth; the other gears were short-shifted. With 102 miles on the clock, both the carb jetting and gearing were off and the motor was still very tight. You can hear the engine blubbering slightly on the some of the upshifts and near top end. A subsequent change of sprockets and dialing-in the carburetor yielded significant improvement. By the time the engine was fully broken-in, top speed on the flat had risen to 67mph...surprising even to us.
  • The same tires, speedo, chain, air filter and exhaust were used with both engines.
  • We never planned to use this strip of road for shootout-style speed tests. This is just a convenient and safe place for short blasts and is close to the shop. The short downhill section gets bikes through the first three gears more quickly than normal and the longer uphill segment gives a good indication of speed potential in a very short & convenient location. Most importantly, with no crossroads, it's also relatively safe. We use this for tuning & testing carburetion and gearing. Shooting video of tests is a handy tool. You can see and hear things through video that are missed while riding in real time. Such was the case with these two video test runs. We originally shot the Z110 run for later study. It wasn't until after the video was reviewed that we even knew the speedo could be seen at top end. Even stranger is the fact that it wasn't until months later when we discovered that the run with the Nice engine installed was a valid side-by-side comparison. The Nice was given less time at WOT, while the Z110, being fully broken in was run wide-open for the entire run in the first video and had a huge WOT runup that the Nice didn't, in the second. What you probably cannot tell is how much more quickly the bike reached an even higher top speed in less distance. The videos, in full resolution (as we have them) ,allow for detailed analysis & comparison allowing us to dissect the runs. Through frame-by-frame comparsion it was discovered that the bike reached 63mph four seconds quicker than it could hit 55mph on the same test strip, prior to the engine change. We may discover more interesting and useful info on videos already in the library. This "shootout" was just a happy accident(!)
 

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