Hi guys. My little project has hit a problem. Yamaha sr125 wont start without a little choke even when warm. When it does start it revs fine but as soon as i pop the choke back in it dies.

When its trying to start it does alot of popping and farting. Here is what ive looked at so far. Had a meter on the ignition coil, all good. Plug good. Stripped and checked the carb. Checked and reset valve timing. Done leak test on carb rubbers. Mixture good. Getting spark and fuel. Im now stumped. Any ideas lads and lasses greatly recieved.

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Sounds like the carb pilot jet could be blocked. Once unscrewed you should be able to just see through it or spray some carb/contact cleaner through it to see if its clear (Don't be tempted to poke bits of wire down it).

Thanks mate but have checked carb and all jets clear. Im thinking it could be crank case pressure or valve guides as the problem started after throttle cable snapped and apparently after a sudden shut down of revs, valve guides can go. Looks like im stripping the top end.

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And where did that wonderous piece of bollocks come from.

Almost every bike on the road will have had the throttle shut quick. Happens most times you use the brakes. People rely on it.

The problem is in the carb. Some add fuel with the choke. Some choke systems strangle the idle air flow.

Any way round its not the valve guides. 

If your adamant the carb is good no2 on my list would be a leaky valve from wear or off adjustment.