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Hi.
I picked up a cheap xr80r for my teenage son. It's a 2003 model I believe. Neither of us have ever done motorcycle mechanic work before but i love diy projects. Here goes...
It was running ok when we first got it, but choke could never be taken completely off. Then at some point while my son was riding it the chain broke. This spurred us on to do little bits of tinkering cause we like learning about how stuff works. It was just minor stuff though, like removing plastics and things.
Then it became harder to start, wouldn't run smoothly, and we discovered fuel was leaking out of the air filter compartment whenever we went out to try starting it.
I then fiddled with air and fuel screws on carby and managed to make it run nice with choke all the way off. But fuel leak still happened.
I dismantled the carby and reassembled, problem was the same.
We bought a replacement carby. Problem the same.
I ran the motor with air filter not attached briefly, still the same.
I fully dismantled cylinder head/piston/cam part of motor.. cleaned up heavy cabon deposits, replaced o rings and gaskets...did it all exactly as manual said to. New oil, new fuel.
Motor runs and sounds good, but fuel still leaks. Valve clearances are good. Rubber boot and gasket between carby and motor are good.
Also, motor seems to only run properly in reserve mode. I have removed fuel valve and cleaned up the filter thingy. Still only runs good on reserve.
The only thing i cant confirm is how good the valve seals are when shut (both before and after removal of carbon) and i have a feeling that cam chain could be a touch stretched? With the circle on cam sprocket pointing up, te t on fly wheel is about 1 cm off from lining up with indicator.
 
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