Main Gearing Whine

soram · Dec 22, 2015

All,
I got one of those 80cc kits at the weekend (great deal and shipping inner EU from Germany if anybody interested). Paid €104 total and was at my door in 4 days....

Anyway, after some faff - not much - it fires up great and I can ride around the road. Main issues on start up were really clutch and chain guide alignment.

But there is a damn awful whine, screech, scrape from the main gears. The engine sounds sweet but this whine is really loud - if it wasn't there the bike would be really nice and quiet. I've searched around but not found any real clues.

I've had the crank cover and clutch plate off. There is no grinding on the cover. The noise is there with the cover off too. If I pull in the clutch then the drive sprocket is disengaged. With the engine running I can then move the main shaft position within the large ring gear by rotating the back wheel. I can see some eccentricity there and when it gets to a certain point the whining starts. A little further and it stops again. When I engage the clutch and drive the whine is there all the time but I guess it oscillates as the gear rotates. The gear teeth do not foul the casing though.
I'd really like to get rid of this - any tips appreciated! I guess I can try to pull off the drive gear and look but it would be great to know what to look for and if this is a standard complaint and if something needs to be shimmed out or if I can just run it and it will go away? Prefer not to do the latter as it is attention drawing!

Any tips / hints appreciated.

Cheers
Stephen

2door · Dec 22, 2015

A little lubrication is suggested on the primary and secondary gears. We usually suggest no more than a dab, about the size of a large pea and spread it around over the gear teeth. Too much grease will eventually find its way into the clutch and friction pads. You don't want that.

Nevertheless I have encountered several primary (small ) gears that were drilled off-center and not concentric with the shaft and I had one that wobbled badly. The noise was a loud, pulsating gear noise that no amout of grease would help. I replaced the gear.

If you can actually see the eccentricity on either gear you might want to give some thought to replacing the bad one. Usually it is the small one that gives the most problem.

Good luck.

Tom

soram · Dec 22, 2015

Thanks, I did look at a lot of posts before my post and have lubricated the gears but unfortunately to no avail. The small dive does look a teeny bit off centre but I'm not sure that is an issue.
The issue seems to be a concentricity issue in the main drive and the clutch. When the clutch is disengaged the big cog rotates around a stationary centre clutch piece. This is OK for some points but if the clutch is rotated internally by rotating the back wheel there is a point where the rotating outer gear starts to whine big time.
I have no idea what it is scraping off unless of course it is just the mesh with the small gear that is getting too close in that position and starts to make noise

I guess I'll have to take it all apart

Stephen

2door · Dec 22, 2015

By removing the spark plug and suspending the rear wheel off the ground and spinning it slowly, clutch engaged, you should be able to rotate the gears, watching closely and seeing what isn't meshing correctly.

There is another area that might need attention and can be the cause of gear/chain noise. I'll post a link that illustrates that issue. http://motorbicycling.com/showthread.php?p=465011#post465011

Tom

soram · Dec 22, 2015

Hi Tom,
It's not a chain side issue. The whine can be reproduced with a stationary chain just by 'repositioning' the clutch inside the main large gear to a different position. I'm new to the whole thing unfortunately but if I find the problem I'm sure it will be of benefit!

I am sure when disengaged the the big cog runs around some rudimentary bearing on the clutch assembly when idling. This bearing surface must have some big run out. I guess I am not sure if the two cogs are just being forced together at some position causing the noise or there is something at the back rubbing.

As I type I am guessing they are being forced together so I will need to take it apart, check the run out and buy a file!

Stephen

Greg58 · Dec 22, 2015

I have had a couple of engines that were very loud when I first started them, one I am still running. Like Tom said if you don't see any wobble in the gears it will probably quite down after you run it a while. Mine makes little to no noise at all now, I like you thought something was wrong when it was new.

2door · Dec 22, 2015

Greg is correct when it comes to quieting after some miles. Things 'settle in', sort of 'self adjust' themselves and the noises go away, to some extent. Maybe just ride the bike for a couple of hundred miles and try to ignore the sounds and see if things don't quiet down a bit. Keep the gears lubricated and hopefully they'll quiet down or...you'll get used to the noise.
If nothing else, reflect on what you paid for the engine and that might tell you something about the quality you can expect. It isn't a Honda or a BMW

Tom

crassius · Dec 22, 2015

in these cases, I just assume one or the other shaft did not get its load properly seated onto the taper of the shaft and loosen both small gear & clutch hub, then seat them firmly straight onto the shaft by putting a socket on them & hitting with large hammer (being sure the woodruff key is nicely in its slot)

except in cases where the piece has been pressed on with the key out of the slot (bending the piece a bit) this will always make it run concentrically again

this can take a while, but the two rules are:

1- don't get in a hurry

2- don't get lazy

soram · Dec 23, 2015

Thanks for the tip. I have no real problem with riding until it is sufficiently worn for the noise to go away but I'd prefer not to be announcing myself so obviously to the local constabulary!

I'll take the drive off over the next couple of days and see if I can re seat or fettle it a bit......

Bikeguy Joe · Dec 23, 2015

I always thought the gear whine made them sound like I was running a blower, haha.
I took it as part of the whole Chinese bicycle engine experience.

Kioshk · Dec 23, 2015

And now, a non-sequitur!

soram said:
I'd prefer not to be announcing myself so obviously to the local constabulary!

A belated welcome, Soram. I had a little chuckle at this, and your name. I have some family members in the Dublin Guardi, and S.O.R.A.M. is a program they implemented in North D. Might want to look it up!

crassius · Dec 23, 2015

Bikeguy Joe said:
I always thought the gear whine made them sound like I was running a blower, haha.
I took it as part of the whole Chinese bicycle engine experience.

true that some motors will be louder than others, as chinese finish work is not always the best - some folks add noise suppressors to inside of covers

Scol · Dec 23, 2015

Where did you get the engine from ? I bought one from the UK and sold it recently and I bought a 4 stroke, I'm hoping to pick up a 2 stroke so I have the best of both.

Shey
Co. Louth.
Ireland

Chaz · Dec 23, 2015

I'm having a bit of trouble understanding your thick accent but I believe that what you're experiencing is the classic Chinese Engine noise. Like someone else mentioned you can buy or make something to go inside the covers to help deaden the sound. It will probably get a little bit quieter as the engine breaks in.

The clutch cover is the worst. It seems to have been designed to amplify the sound of the gears. You can put the palm of your hand over it and hear the difference, nut it's not recommended that you do this while riding unless you have an extra long right arm.

good luck

sbest · Dec 23, 2015

After 3 tanks of fuel my gear whine has finally quieted down.
I'd suggest that grease the size of a pea on the gears is too much. I use a wad the size of a match-head and apply it with a match stick. I don't know about the run-out however.

Steve

dbledsoe · Dec 24, 2015

I'm another who had a noisy (whiny) gear set on a GT5 engine that quieted considerably over time. Initially I thought my neighbor's were staring at me as I rode by because of the jet turbine like noises coming from the motor. As it quieted over time they were still staring when I rode by. I now attribute their stares to either me zooming by so quickly on a bicycle without my legs/feet moving the pedals, or it's the really funny looking helmet I wear.

Don

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