Re: The Official Yamaha Chappy (LB50) Thread!!!

unicorn sighting!

alas too rich for my blood... :(

Re: The Official Yamaha Chappy (LB50) Thread!!!

Jack Rutherford /

Near Cleveland, Ohio

Re: The Official Yamaha Chappy (LB50) Thread!!!

Jack Rutherford /

for sale Cedar Lake, Indiana

Re: The Official Yamaha Chappy (LB50) Thread!!!

still testing things, but i have to say that the clutch characteristics are remarkably dependent on the tranny oil.

like dillon, i've been annoyed by how quickly 1st gear grabs especially once the cases are nice and toasty after summer stop and go traffic, bogging down hard on launch. in my case it also happened during the upshift to second, getting stuck in the no-mans-land of sub 4k rpm.

first i tried a "grippier" oil by topping off with a bit of pennzoil synchromesh MT fluid. unsurprisingly it made the problem worse.

i drained and refilled with mobil1 5w40. a bit better than the syncromesh blend, the multiweight synthetic didn't change characteristics with case temperature as much, but still got too rapid clutch engagement.

i did a partial drain and added some (about 4 oz) STP engine oil treatment. the bottles i had were from the 90s so it was the high ZDDP formula that they used to use (i hear the current off the shelf version has less zinc). it's very thick stuff, almost molasses, and is primarily a viscosity booster.

long story short it made a tremendous difference in shifting characteristics. now 1st gear grabs very gradually from a stop and i don't get the quick RPM drop as before. not only that, it actually winds 1st out and then i can feel second start to ramp up. it almost feels like there's a variator for those few seconds of transition where rpms are steady around 5k but speed is increasing. then second is fully engaged.

i did note a slight drop in flat out, probably due to the increased viscosity and fluid losses, maybe 1mph on top. i have been watching for excessive slippage at lower speeds and haven't noted any yet.

being thicker i'm not sure if this will be a good colder weather mix but time will tell. the bottom line is that the bike became a lot less stressful and more fun to ride in this warm weather with some small changes in tranny lube.


Re: The Official Yamaha Chappy (LB50) Thread!!!

had a 40 mile day yesterday (route on Google maps) and did some math after topping off the tank, netted 57mpg. not bad considering how many minutes were at wot.

also finally got my hands on a 10 and 12.5 pilot jet. swapped the 15 that was in there for the 12.5. the 15 was 3 turns out and wanted more. the 12.5 sits perfect at 1.75 turns out. tiny throttle adjustments while coasting have cleaned up. that just happened this afternoon and I've only got a few miles logged but so far im pleased. (edited)

Re: The Official Yamaha Chappy (LB50) Thread!!!

Eric Migliorino /

What tires does everyone use on their chappy’s? I have the stock 4.00 x 8 tires.

Does anyone use the thinner 3.50 x 8 tires? Any reason to go with the thinner tires? I would think the slightly wider tires would be more stable.

I have a set of Shinko white walls - 4.00 x 8 tires but need to mount them. Anyone else have good luck with these tires? Obviously cheaper than stock tires.

Re: The Official Yamaha Chappy (LB50) Thread!!!

> I have a set of Shinko white walls - 4.00 x 8 tires but need to mount

> them. Anyone else have good luck with these tires? Obviously cheaper

> than stock tires.

i've been running those WW shinkos for a little over 1k miles now. they're a bit taller than oem tires so speedo reads about 8% low. run 15psi front/30psi rear. tread life is good, traction is good. little slippy in wet but what isn't? biggest pita is keeping the rear sidewall clean since the white shows everything.

Re: The Official Yamaha Chappy (LB50) Thread!!!

Eric Migliorino /

Anyone use the Michelin s83’s?

Re: The Official Yamaha Chappy (LB50) Thread!!!

finally got my hands on a 28t rear and slapped it on last night. combined with the 16t front the FD ratio is 0.571. oem on the lb50j was 13/32 which is 0.406. total ratio change is 41%.

compared to what i was running before today (16/32, 0.500, 23% taller than oem) i jumped up 14%. in theory picking up 5mph top speed. didn't have road to test flat out during the commute this morning.

however i have geared up too far imo and acceleration is now too sluggish for my driving patterns. maybe if i had more long stretches it would be worth it.

it's easier to swap the front sprocket and i have 13t, 15t, and 16t available. i'm going to stay 28t in back and drop back down to 15t in the front which will give me 0.536, (32% taller from oem and halfway between today and yesterday).

i also bit the bullet with the treats sale and grabbed a MLM PP, so a lot of this fucking around will probably have to be repeated. (edited)

Re: The Official Yamaha Chappy (LB50) Thread!!!


Your gearing experience seems to be consistent with mine as well as Jack's. My LB80 has 15/28 gearing. Only modification is the MLM people's pipe. The gearing is just ever too all, even down here in south florida where its all flat. I think 15/30 gearing would probably be ideal. Not much is gained in top speed by changing from 14t to 15t (other than lower cruising RPMs) . so maybe 14/28 would be better if your commute has hills. I want to say on these bikes +1t in the front is equivalent to +3t out back. Keep us posted with your findings.


Re: The Official Yamaha Chappy (LB50) Thread!!!

slapped the 15t front on and pickup is much better vs 16t. treats won't be in hand until Thursday so I might mess around some more and try the oem 13t in front w/the 28 rear.

Re: The Official Yamaha Chappy (LB50) Thread!!!

went back to oem 13t in front with the 28 in the rear. this is shorter (0.46) than I was running for a long time (16/32, 0.50) and an even bigger change from what I was last on (15/28, 0.53).

as expected rpms went up, acceleration went up. top speed changed less than expected... with 0.53 I could sit at 45mph on a long stretch. with 0.50 it was around 43, and with 0.46 it was 41.

I've found as it sits my motor doesnt appreciate sitting past 8k5 or so. I felt the slightest hint of a seize coming on during some sustained pulls with the lower gearing. since i have the sudco adjustable main I immediately richened it up but then at 8k5 it was just starting to 4 stroke. anything past that and it got worse. so when richer speed was limited by 4 stroking, but leaner was too hot. (this is at 20:1 too.)

at this point it's starting to seem like 0.50 is a sweet spot in terms of revs/top speed. to that end I just snagged a 14t front off Amazon and I'll go back to that to compare.

getting pretty quick at these front sprocket changes now... lol

Chappy & Chappy Stuff


Stock Chappy with an exhaust leak

Second engine

Used 70cc kit

MLM pipe


Re: Chappy & Chappy Stuff

Jack Rutherford /

Re: Chappy & Chappy Stuff

Can’t wait to see how this turns out

Re: Chappy & Chappy Stuff

Jack Rutherford /

Hopefully, well.

Re: Chappy & Chappy Stuff

been holding off to collect more info so i could make a big post here, then i fubared a piston which set me back a few days... but i have a lot of info to contribute.

so one of the big complaints with these chappys is the transmission. not the robustness, which seems pretty much unparalleled in the moped world, but rather the tuneability of shift points. as the builds get more screamer the very low rpm engagement for both gears means a lot of bogging down.

many pages back dillon went at his first gear clutch to see if he could squeeze out a higher stall for help on takeoff. unfortunately despite taking a few coils off it made little to no difference.

i tried messing around with fluid mixes and found some success, but not enough to satisfy.

i tried drilling a few holes to lighten the shoes, and i could barely tell the difference. (admittedly they were not in the best location, just on some casting buttons.)


so i started looking at the springs. original dimensions:


i measured the pull tension of both 1st and 2nd gear OEM springs. interestingly, both came up at 8lbs/in, and had identical dimensions, despite having different part numbers. i tried swapping one for the other and i could tell absolutely no difference in performance.

going for broke i went ahead and ordered two sets of the heaviest off the shelf garter springs of "looks close enough" dimensions i could find: comet 216115A ( i got them from ).

to my happy surprise they turned out to be almost exactly the same length as OEM:



Re: Chappy & Chappy Stuff

however, the diameter of the comet spring was quite a bit larger:


the circumferential channel for the spring through the alignment plates was not large enough to fit.


so out came the dremel...



Re: Chappy & Chappy Stuff

despite getting the comet spring into the channel of a single shoe, as dillon can attest threading the bastard through all three is another thing entirely (never mind hooking the ends together). the comet springs had some hefty tension compared to OEM. i tested a virgin spring at 35lbs/in.


so two things were working against me: the clearance from spring to channel, and the massive spring tension. i decided to kill two birds with one stone by sanding the outside of the spring with a flap wheel. i brought the diameter from 7.36mm down to 7.22mm:


i also gave it a few pulls to break it in a bit, and was left with a hair under 30lbs/in:


now we're talking!


Re: Chappy & Chappy Stuff

now, the real challenge was left... get the thing threaded through, and hook the ends.

i worked out a technique that might be of use to others. it requires a vise (to hold the clutch), two vise grips, and two short sections of stainless safety wire.

make two loops with the safety wire and clamp the ends securely with the vise grips. use the loops to hook the ends of the spring and pull them across each other.


at one point, in order to work the "slack" of the spring around to the loose ends, i put a drywall screw into the scrap wood which held one vise grip in position. then i pulled on the other vise grip while nudging the spring towards the loose end.

the advantage of the safety wire is that once hooked, the wires can simply be cut off, instead of trying to get a hook or some other appendage out of the spring loops.

there was gratuitous cursing and swearing.

finally, success:


i cleaned everything off, put it all back together, refilled fluid, and went around the block. the sonofabitch worked, and pretty well. whereas 1st gear used to start engaging very low, around 2-2.5k rpms, now it was at least 1.5k higher, between 3.5 and 4k. not as high as i wanted (5k) but still a massive improvement.

one thing i noticed is an odd consequence of the mismatched spring tensions and the way the chappy tranny works...

so the crank spins the 1st gear clutch, but the 2nd gear clutch does not rotate until the bike is moving. at a rest it is not spinning at all.

as the throttle is opened, 1st gear engages the clutch bell, which is coupled to the 1st driven gear. sprags on that 1st driven gear turn the jackshaft, and ultimately the output sprocket.

as ground speed increases, the second gear clutch rpm starts to increase since it is being "reverse driven" by the shared jackshaft, but it is spinning at a slower rate due to the gear ratio difference. at some point its shoes contact the clutch bell which is coupled to the crankshaft via the 1st gear clutch shoes. the bell is spinning faster than the clutch is, so when the clutch fully engages the shoes transition from "slipping" to "engaged" rather abruptly. the 1st gear driven gear is now "freewheeling" with it's sprags as it is overdriven.

this method of securely engaging 2nd means there is some hysteresis to 2nd gear, since once engaged it is spinning at crank rpm, which is faster than it was with 1st engaged.

i found quickly that i had strange situations like 2nd was engaged, but 1st wasn't. ie, i felt the clutch slipping, but it was the 1st gear clutch with the higher stall point.

this did not strike me as very good for the first gear clutch longevity, so i repeated the whole process again for second gear... (edited)

Re: Chappy & Chappy Stuff

when all was said and done, the ped rides better than ever. 1st gear comes on around 4k and winds out to 9k, then second ramps up. because of the hysteresis of 2nd i still have to drop down forward speed to a lower point than i'd want in order to trigger a "downshift," but it's not nearly as bad as it was before. the bike is more "point and shoot" at low speeds which was a flaw that really reduced the fun factor.

i ordered two sets of two springs so i have two spares that have been left unsanded. the next time i open the tranny i'm going to swap 1st gear to one of those unsanded 35lb springs to see if i can squeeze just a little bit more out of it. i will also get more aggressive with weight removal from the shoes, especially the outboard tips.

Re: Chappy & Chappy Stuff

a few final notes:

not only are 1st and 2nd gear springs indiscernibly different but also the shoes. i was able to mix/match shoes from one clutch to the other and they were identical.

based on this knowledge and careful looking at pictures, i ordered a pair of clutch assemblies for an LB80 off the internet. the shoes have a different part number but are physically identical:


i also noticed that 1st gear on an LB80 has a different hub design with three extra holes. i don't know if that's an lb80/lb50 thing, or it could be year of manufacture. i prefer the holed version due to rotating mass reduction and may end up using this hub in the future.

Re: Chappy Recommended Transmission fluid

I put a lifan 125 in my 78 lb80. It took some minor changes to mount, but love it. Had to bulk up some of the frame at mounts as the 125 was shaking the s&*# out of it...

Re: Chappy Recommended Transmission fluid

Any pictures?

Re: The Official Yamaha Chappy (LB50) Thread!!!

Jack Rutherford /

Re: The Official Yamaha Chappy (LB50) Thread!!!

good stuff Jack!

when you were kicking it over I immediately thought of this:

Re: The Official Yamaha Chappy (LB50) Thread!!!

Jack Rutherford /

Thanks Ken, that was hilarious! Next time I'll say, Aw Fer Krist's Sakes, C'mon!

I'll test out the acceleration soon. With that tiny mini-rotor, acceleration should be much better and now I can advance the timing. Hopefully, I can avoid getting into serious clutch surgery but, if not, your guide will be invaluable. Thanks.

Btw, the pw50 offset timing key sold at should work in the Chappy to advance timing 3.6 degrees as it appears the Chappy key is the same dimensions as the qt50 key and thus the pw50 key.



Re: The Official Yamaha Chappy (LB50) Thread!!!

Jack Rutherford /

more potential Chappy info.


I put this headlight on the qt50 and it should work on the Chappy. I just had to put some washers between the rack and the bucket to get the spacing right. It has a removable bulb. I needed to go 12v on the qt and now the Chappy as a result of the HPI system. This appears to be the same headlight but you have to order it from overseas. It basically replaces the entire headlight assembly so you lose the painted bucket that came with your Chappy although I've seen several Chappy's with damaged headlights so it may be no big deal. I'll report back later with more info.

Re: The Official Yamaha Chappy (LB50) Thread!!!

Wow Ken! Just WOW

Finally got around to reading your transmission mods. You are the guru of the chappy trans! Your technique using the vice grips is invaluable. I love how in depth you go with your process. You are on the leading edge of Chappy transmission innovation. Keep up the good work

Re: The Official Yamaha Chappy (LB50) Thread!!!

Terbo Speghetti /

Post #420

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