Suzuki Smash 110 Noisy Drivetrain

[MaiChai]

This bike was fine until the gf lent it to her younger brother so he could use it for going to school; while in his possession he has thrashed it, and we have just had the rear brake and exhaust put back in order, put the number plate back on, but the rear light cluster back, and put back screws and stuff to make it road worthy. This lot cost a couple of thousand baht, and we decided to put off the noisy engine problem so as the spread the cost of the repair. I recently replaced a piston in a Honda Wave 125, and thus have got interested in more advanced repairs on motorbikes. So I thought I would have a go at this, rather than paying over the odds to a local mechanic (and they will charge if its a major repair). Needless to say we are very disappointment with the way he has treated what is in effect a good deed from our part; basically he gets a motorbike for free and he has thrashed it. Now I will not be doing anything for him again.

Basically its Honda Wave/Cub clone with auto clutch (centrifugal clutch). This means when the engine reaches a certain speed, the clutch engages; also when you change gears, the gearbox takes care of the clutch. I have got hold of several old Honda Cub repair manuals, and this looks very similar.

The engine makes a rubbing noise, even when standing still. It sounds like the part of the clutch fixed to the engine side (the centralfugal part), or could even be a bearing. Not had the chance to open it up yet. Any suggestions on what the problem could be?

[Lickey]

MaiChai,

Kids in our village hold the gear selector pedal down, rev the engine and let the pedal up, this holding the pedal down effectivley acts like a manual clutch as you know, they also stamp through the gears without relaxing engine revs,

Centrifugal clutches will not stand much of this kind of abuse, The rubbing noise could be 1 of 2 things, the bonded lining has come of the shoe or the return spring/s have broken due to eccesive heat.

More the latter i would think, if a lining had come off, it possibly could jam into the other lining and caused perpetual motion once a gear was selected.

Definitley a time for a looksee, Cheers.

[MaiChai]

Kids in our village hold the gear selector pedal down, rev the engine and let the pedal up

Gf advises the little rotter has been doing this

Thanks for the reply. I have still not got round to opening it up (although have bought a gasket set in anticipation). Hope to take a look this week.

Took a trip over to Nontaburi from Ladprao today on the bike and its still holding up. Seems like the problem can stall the engine when the engine isnt quite warmed up. Other bike was off the road so had to use this one, but other bike is now operational so can take a look at this one (always need one bike operational before I can take the other one apart).

Edited June 8, 2008 by MaiChai

[MaiChai]

I had time to take it apart, and there seems two problems:

-Exhaust valve seems to stick, which would explain the noisy exhaust. Cam chain also seems noisy too, so that probably needs inspecting and replacing.

-A rubbing noise from deep inside; hard to place this noise, but it sounds like a major bearing and not the clutch.

Aside from this, the drive is interesting. It has in effect, two clutches. One is the centralfugal clutch, and the second is a regular clutch, which is actuated from the gear shift. The first clutch consists of three brake pads that swing out when the engine gets up some speed. Explains why a friends Wave with traditional clutch is cheaper new than the auto clutch (one clutch instead of two). Looking at the Honda Cub manuals and its seems like this has only one clutch, and this more modern arrangement is designed to be heavier duty and thus more resilient to heavy Asian family use?

Anyway, still not much time to delve any deeper. Seems like we can leave it longer until its gets unbearably noisy or something breaks.