clunking sound coming from 3-speed semi-auto with reverse

[bsheppar]

I have the 125cc Loncin engine with 3 speed semi-auto with reverse. It runs great, plenty of power, and it shifts fine BUT it has a clunking sound coming from the back part of the engine where the transmission is. You can hear it in any gear plus reverse and at any speed. Could it be just a chipped tooth on one of the gears? Or is it something more serious? How hard is it to get in where the gears are?

http://www.peaceindustrygroup.com/details.asp?id=326

[katoranger]

To replace gears it requires complete disassembly of the engine. Are you sure that the chain/sprockets and the clutch are all adjusted properly.

Allen

[bsheppar]

the chain and sprockets seem to be running true to each other and the chain is nice and tight. And since i replaced the swingarm bushings, the issue of the chain jumping off is no more. Are there any other adjustments that i can make that i don't know about?

[katoranger]

Is the chain too tight? Sprockets are not loose?

We are getting beyond my level of knowledge on this so hopefully someone else will chime in.

Allen

[chrism1]

make sure all engine mounting bolts are tight and not broken,also check the swingarm bolt!!! :)

[VinceDrake]

Other thing to check, Check for siezed links in the chain-- Was out sand blasting on my ZMC last weekend, and geez does that make a brutal noise when a couple links lock up in the chain!

--Vince

[DesertDog]

I have the 125cc Loncin engine with 3 speed semi-auto with reverse. It runs great, plenty of power, and it shifts fine BUT it has a clunking sound coming from the back part of the engine where the transmission is. You can hear it in any gear plus reverse and at any speed. Could it be just a chipped tooth on one of the gears? Or is it something more serious? How hard is it to get in where the gears are?

http://www.peaceindustrygroup.com/details.asp?id=326

be very specific on the where abouts b-4 you go tearing into it and find out it was something totally different,
just my opinion, measure twice and cut once 8O ,

that motor has pretty good torque so check all the mounts, to the shock its self, and the swing arm

what type of bike do you have ,? can you post any pics

DD

[bsheppar]

I'll be sure and check all the nuts and bolts and lube up the chain real well.

[/img]http://www.peaceindustrygroup.com/Upload/200781323495053857.jpg[img

[yurkia]

had a wierd rattling on the front of my bike when you really got on the throttle. brother thought it was something in the engine itself (timing gear, exhaust manifold, etc). turned out to be a loose bolt in the skid plate.
Moral of the story: check the easy stuff first!

[DesertDog]

I'll be sure and check all the nuts and bolts and lube up the chain real well.

[/img]http://www.peaceindustrygroup.com/Upload/200781323495053857.jpg[img

sorry BS, you did link that, i'm tired.

uh lift it off the ground , hopefully you have a lift of some sort, milk crate or a harbor frieght tool atv 39" lift cart, start it up put it in gear and go from there, i do alot of sound , walk around checks that way on mine,

with it shut off grab the rear tires or axle and try to move it , and so on , check check check
oh yeah that was said b-4

[bsheppar]

i've checked all the bolts, brackets, bushings, chain, etc and they're all good. When i lift the rear end off the ground, crank it up and put it gear, i don't hear the noise unless i press the rear brake to add a little resistance - and this is in all gears. the sound is definitely coming from the transmission area so i figure it has to be a tranny issue. maybe a chipped tooth on a gear possibly? can you get to the gears by taking off the right side cover of the engine? it looks like it's held on by 5 or 6 bolts. has anyone had the loncin 110 or 125cc engine apart yet?

[VinceDrake]

One more thing-- Maybe make sure *ALL* the teeth are intact on the *FRONT* Sprocket. Could cause nasty clunking noise under load.
(Rd350 got me once that way...)

--Vince

[katoranger]

You need to split the engine cases to remove the gears. Requires pulling the engine then the top end and essentially an entire tear down.

Allen

[warrior91]

Are your bolts loose holding on brake rotor? How about splines worn on sprocket or brake hubs???

[bsheppar]

i checked the sprocket teeth and all is good there and checked all the bolts. i'm pretty sure it's internal. everything seems to work fine it just has an annoying knocking sound coming from the transmission area. anyway my son and i went down to broadriver atv park all day saturday and put another 50 or so miles on it with no trouble at all. the chain never came off, nothing shook loose, not a single problem. And it was dry, rutty and rough out there. My son is at the age (10) where he has only 2 speeds - fast and faster so believe me when i say he doesn't baby this thing at all. The only thing i did see wrong was on the rear shock it looks like the bushing is wearing out where it mounts to the swingarm. Anyway, if the knocking gets worse or it stops shifting properly then i'll definitely tear into and see what's going on.

[VinceDrake]

Just for my own curiosity, Just a couple of questions:

--Does it ever pop out of gear (Either under deceleration or accel?)
--Does the awful clunking transmit itself through the bike?, i.e. can you feel it under load as well as hear it?
--What's the rear axle/chain alignment like?

I'm *really* reaching here, but *maybe,* just maybe, I've noticed the drive spockets tend to fit on the output shaft really poorly, possibly, if your (the Bikes, not your buttocks) rear end was really out of line, it could cause the drive sprocket to flop around on the output shaft and kind of cock over and release, type of thing, kind of like a bad U-joint... Most likely would drop chains, but like I said, I'm reaching here....

If no, I'd have to agree, you're likely going to have to go into the engine/trans. Although, if you're just going to run it for a bit, it might not be a bad idea to put in a magnetic drain plug or something, incase it has damaged a tooth or bearing-- Just to catch the pieces so they don't go somewhere disastrous...

Or you could do what I do, and blow it up good, so it's nice and obvious :D

--Vince