Hi All.. I have a had a weird problem with my 2006 Rev 3.....

I was riding in a Trial a couple of weeks ago and after the 14th section the bike started to vibrate and make a noise like the mains/bigend had gone.I pushed it back to the car park where I started it again and asked a few people what they thought the problem was and they said mains/bigend.!!!

So today I took it to a reputable mechanic for him to take a look at...So I started it ( first kick as usual) and guess what no noise or vibration at all !!.

Does anyone have any ideas ??Surely if it were mains/bigend it would be noticable all the time !!!

Any thoughts /comments gratefully appreciated..

i would try engine bolts.if it was mains it would not cure itself?

Had a similar problem a few years ago, quarter turn with a spanner cured it.

What model Beta are you riding? If it is an Rev 3 08 and you can't find any loose engine bolts or flywheel then I would take a close look at the main bearings as there have been many reported failures.

I think i read a post about someone having the same sort of problem, It turned out to be flywheel weight was loose!

other than that i dont know!

Main bearings sound more like grinding, and from what i know big ends is a distinctive knock, If it didnt do it when you started it the second time it could be something to do with engine temp!

Hope this helps