Hey guys, bike blew up not long ago. I have an aftermarket exhaust which burns oil really quick. Bike was serviced 3 weeks ago and it was still running on no oil! It lost it's power while riding, was smoking pretty bad and it has no compression now. I know that it's piston rings and cylinder 100% and I've got my parts here already. I have no idea how to fix it and I'm not taking it to a garage as they will charge me for a "new engine" when they will simply replace the parts. I've got the bike taken apart all I need to do now is fit piston and cylinder. Anyone could help? Like guide me. I have the tools. And if you are thinking of what bike I've got, it's a little 125. I know, I know. I'm not old enough to do my full licence.

An exhaust doesn't burn oil!

Strikes me that if you don't get the job done properly, you're only going to have more problems.

Sorry, but that's just the hard truth that I've learnt over the years.

See if you can find an independent mechanic willing to do 'homers' and although it'll cost, at least it'll be less than at a garage, and you might get to help and learn a few things in the process :-)

It does, trust me. It backfires a lot so it spits everything out plus it doesn't have a baffle.
I've done mechanics in college, never fitted a piston though :/
And yeah I've got a mechanic coming in tomorrow, will get it done for around £100 :)                                                                                                                                                                             

Kazz. Sounds like the piston and rings ate worn causing back pressure forcing oil to be burnt via the intake. Is the air filter full of oil? You will need to check if the cylinder needs a rebore, as fitting a new piston will not sort it if the barrel is worn. What bike is it? You may be able to get a top end from a breaker cheap, then you just need a gasket set and a torque wrench!

Hi Kazz, If your barrel and piston are off take the top piston ring off the piston and put it in the barrel just below the top of the marks it made when running. When its level measure the gap at the ends with feeler gauges then you can check it against the manufactures specification. If you then move it right to the top inside the bore and re measure the gap you will get a good indication of bore and ring condition.

Hey guys I've got it sorted 4 months ago, took the engine apart and the piston was melted. Got the engine rebuilt and its running fine ??                                                                                                                                                                             

Excellent, glad you got it sorted

Hopefully whatever issue caused the piston to melt doesn't happen again!!