Vibration in engine

[laladownunder]

Hi Karl, I meant, that with the timing chain and new tensioner in place, if I turn the variator by hand there is instant movement on the cam. Checked the blades on variator and all the blades in place. I told a friend about what you said, move the crank up, down and sideways, He reacon that even that I could find no movement, it can still be the crank bearing in the block ( split casing in this case ) on variator side that worn away the bearing hole / seat just slightly now causing the outer race of bearing to actually turn in the casing. When idling, no vibration, when revving up it start vibrating. He even recon that there is maybe nothing wrong with the bearing, it just ate away the alum casing. What u recon

[CROSSBOLT]

Sounds like it is time to completely dis-assemble the engine and inspect everything.

Karl

[tortoise]

maybe nothing wrong with the bearing, it just ate away the alum casing

Unlikely . . crankshaft and connecting rod bearing failure is typical with 139QMB big-bore-kit installations, but somewhat rare for stock 50cc's.

[star667]

Now this is coming from a older mechanic I am honestly not to familar with this scooter but the usual assumption if there is any vibration on the crank its a bad bearing knowing that don't run it anymore even if it is not it pays to be careful better that then paying for a new crank

[laladownunder]

Thanks Tortoise, with no up down side way movement, I still think it to be the crank bearing, it just started and I have not driven it again, just fishing out to what might be the problem.

[laladownunder]

Hi, thanks Karl, yup I am going to do it this weekend and hopefully it is only the bearing

[laladownunder]

star667, I tend to agree with you and will strip it this weekend, Lucky I did not continue riding it when vibration started and hopefully it is just the roller bearing

[laladownunder]

Thank you for everyone making an effort to help me. I think I am on the right track now and will not strip the engine for nothing, must be a bearing. Thanks

[CROSSBOLT]

Don't take too long. I am holding my breath to find out what you find in that thing!

Karl

[paceneedsstides]

I bet bad bearing

[laladownunder]

Well, here we got it. It is the bearing on the variator side. Seems a bid of a grind - very softly - but enough for me to replace. Also there is ringmarks on outer racer indicating the bearing was turning in the seat/ hole. Will have to get a new crank as it seems like one hellofa job replasing bearing and will have to knurl the bearing seat/hole for a tap in fit - now both bearing slide in and out with hands only.

[CROSSBOLT]

Don't forget about a Loctite product called "bearing mount" for just such an occasion as yours. I used it years ago on a SAAB transmission and it worked perfectly! Inside knurling is nearly impossible to find a shop that has the tooling. Need the whole crank just for the bearing? Gotta be some way to get that thing off.

Karl