hi all,my 2011 ossa has developed a vibration at about 2/3rds throttle. up to that point all sounds well and starts fine.I cant find anything loose anywhere to cause it.The spark plug was black and a bit oily so I was wondering if the tps was a bit out would it cause the vibration.

 

Sounds like crank bearings.You can pull the left cover to check that one.

I agree with ric h, that it could be the crank bearings. The left side has a caged needle roller bearing, the axial control of the crankshaft is only down to the right side ball race, a similar bearing to the ones used by GG. If this has worn, then you would tend to feel vibrations through the footrests, getting worse as the revs rise, you would be able to hear it too as a rumbling noise. The TPS would not cause this vibration. There is no other way to check that this right side bearing has failed, only from the motor vibration and the sound. It is not an easy bearing to replace, you would need an Ossa crank bearing, while it is the same type as a GG and JGAS, the Ossa bearing has a short slot machined in the outer casing to locate a 3mm allen screw. Ask for help locally to determine what the vibration is, if it is not that bad, it could be that something has come loose in the fuel tank, pump or filter. Bye, Peter B.

thanks for the replies,the vibration seems to be at the top of the engine and starts at a certain rev,otherwise she sounds good.