I bought a 2002 yamaha blaster rebuilt top end. New wisco piston and only bored cycl. 20 over. started up second kick. rode great about 3 hrs then parkes it. It ran great. I put 93 gas with yamalube in mix in the oil mix tank. now starts great wont idel well and has a little backfire to it. any ideas? thanks

this happened with my sons pw50 where the piston ring had snapped and when it locked it was stuck bewteen the piston & bore

i would seek a shop or mechaninc to look at the top end and isnpect the piston & rings for wear or damage

dont keep kicking as this could result in further damage

Raise the back wheel with a stand and see if it starts and wheel spins. With it still on stand kick down thru gears and see if you really are in neutral. Pull in clutch and try to brake back wheel. To me it sounds like a gearbox issue if you really are in neutral (expensive) but could also be a clutch cable (cheap).

you probably seized the engine. The piston rings have most likely scored the cylinder wall. At the very least you will have to rebuild the top end. Oversize rebuild kits are available. You will have to have the cylinder bored to a larger diameter to accept the oversize piston kit.

http://cgi.ebay.com/ebaymotors/Yamaha-Blaster-040-Platinum-Piston-Engine-Rebuild-Kit-_W0QQcmdZViewItemQQhashZitem1c1ad757dbQQitemZ120709404635QQptZMotorsQ5fATVQ5fPartsQ5fAccessories

The crankshaft is also lubricated by the oil in the fuel. There is a possibility that the crankshaft is also toast due to lack of lubrication. You will have to tear the engine down (top end) to verify the damage. you could remove the exhaust and look into the exhaust port to view the condition of the piston.

You may be able to find a used engine at a reasonable cost from the internet. Google search.

Smoke in a two stroke motor is caused by two things. 1) Even a four stroke will smoke if it has too rich of a mixture or a carburetor that has a malfunctioning choke (a new choke plunger would fix this). Make sure you have a good o-ring on the main jet holder. This was a common problem on old Yamaha two stroke carburetors.2) The type of oil you are using is of a very low grade. Smokeless oils and synthetic oils will smoke less and could solve the problem.
You could just be seeing old residue burning out of the exhaust system, try cleaning the baffle. When you rebuilt the motor did you use a semi drying liquid type gasket material between the two case halves? This would keep transmission oil from leaking into the crankcase. If you have only started the motor in the driveway you may have to just go out for a long drive down the road to clean up all the systems.

If you can turn your engine over by hand easily by pushing down the kick lever, and your not Arnold Schwarzenegger, You have a compression problem. Do a compression check. If your bike has under 100 PSI you need to disassemble the top end , bore or hone the cylinder (depending on condition) and install a new piston, rings, and gaskets. This should fix low compression. If the lever is going down but the motor is not turning over then you need to remove the side cover and check for broken kick gears. Reed valves have nothing to do with this problem.

did you check the clearances between piston & bore it sounds very much like its time for a rebore & oversize piston that is a top end rebuild rather than just a clean up

Hi I am vortash .. firstly 32 - to - 1 may be a tad high I would say ... it would be fine at the same as the ducati ratio 20-to -1 with a good quality oil , you should check that your sump is not filling with oil as this will cause performance problems with backpressure .. but maybe the best thing to do would be to replace the oil pump and run it as it was designed to do ?. I am sure you will get one off the net cheaply or from a local bike breakers .... Regards Vortash

re- strip top end, hone cylinder bore and then re-assemble piston, rings and cylinder dry, yes that's correct use no oil on piston assy. apart from gudgeon pin. Has the valve stem seals been replaced?

could be the ignition control box, I would try locateing a used one and trying that first. Good luck