Hi - just joined and hoping to get some pointers.

My Wuyang WY125-24B (Honda Innova clone) is not behaving itself...

In the last couple of weeks I've noticed some excessive vibration through the seat and foot rests. Here's some detail I hope might help:

- it happens when I'm on a 'balanced' throttle and when off the throttle - very noticeable when I first roll off the throttle
- not at all evident when accelerating
- appears to be rev related, fairly high up the rev range but do not have a counter so can't be more specific. Get it in 3rd gear at about 32-35mph and 4th gear at 40-45 mph, also when revving in neutral as revs start to fall
- engine is not showing any other signs of ill health: no increase in oil usage, no change in power output (still underpowered ;o)

Last weekend, I thought I'd best just tick off the usual culprits to ensure it wasn't anything simple, so changed the spark plug (old one was fine), adjusted plug gap and checked and adjusted valve clearances. The oil was fairly recently changed so I left that, but just checked the level again. After that the engine started a bit more brightly (though it was starting fine before) and it idled a bit better, but nothing I wouldn't expect from a brand new NGK and valve clearance adjustment.

I warmed her up for a few minutes and then revved it a bit on the centre stand - still got the vibrations and it made the bike creep backwards. Bit of a surprise, but it could be normal?

Used it Monday and Tuesday but now together with the vibration, there's a new noise that accompanies it. I'm calling it a fluttering flappy sound. It's not popping from the exhaust - it's more mechanical.

I've tried holding onto every bit of the bike I can find while revving the engine in the hope it's a loose bolt, but it's still there and sounds like it's in the engine, though it's not easy to locate as it's a low pitch.

So, where should I concentrate my diagnosis? Could this be a bottom end issue? If it was valves/rings then I'd expect increased oil consumption, a smokey exhaust and/or a loss of power.

I had a Honda C90 before and kept the Haynes manual. The closest symptom in the engine troubleshooting section points to:
- Excessive run-out of crankshaft
- Worn crankshaft bearings (rumble)
- Worn connecting rod or big end (knock)

I don't think it's a knocking or rumbling sound.

Any ideas?

Cheers,

Matt