I got a new bike from my mate and all of a sudden everytime I start it it runs for about 15seconds with full revs and doesnt go very fast and then cuts out. It sounds really loud defferently not healthy I got told itwas the piston rings but idk I have changed fuel and clean air filter I have to bump start it as the kickstart doesnt work but sometimes it does. And I would like to know what is wrong with it befor I take it to a garage

JackM, October 2013

Hi,

You need to ensure that if the piston rings are worn enough to need changing (as you were told), that the cylinder bore is ok.
No point doing half a job because if you have fitted standard size piston rings when you have a worn cylinder you will lose compression.

Cheers

westcountry, October 2013