Starting and running problem

[supermoto1962]

Can anyone help with this problem:

I have an XLR250 which i bought as a non-runner. A little work and it now starts, runs for about one or two minutes then stops.

So far:
1. Cleaned and set carb as per manual
2. Fitted inline fuel filter
3. Installed a good working plug & checked for good spark
4. Set inlet/outlet valves
5. Checked electrical connections are good.

It will start with choke fully out and no throttle. Engine seems to rev quite high. Reducing choke to half the bike will revs freely.
Throttle can be blipped and less choke applied but all of a sudden engine stops.

Sometimes it will start if kicked up at once but more often it refuses.
Leave it for a while (usually while i remove plug to check if it's fouled) and it can be started again but same thing happens.

At a loss now. Any idea's? Don't have any spares to try.
Regards

[stretchy]

That's a tricky one but I'd start with the electrical bit (poss because I'm an Electronic eng!)

So Coil going open or CDI going funny. Coil first but as you have no spares maybe a little trickier to suss. There's also the stator and pulse gen for the timing.

Does sound electrical.

[andreww5680]

I had a yamaha xt550 that would idle and not rev and it would idle for as long as you liked, as soon as you revved it , it would cut out - turned out to be the bottom coils (alternator etc) once rewired it was fine. Check every connection, if necessary clean connections and possibly remove things from the running circuit to try and isolate the problem. This is the first step as well as the inexpensive step. If you have no joy maybe look at coils, cdi, pick up coils or bottom coils- i have heard side stand switches can give trouble- check everything.

[pistonbroke]

Is the breather on the fuel cap blocked? Try unscrewing it slightly(the fuel cap) and run the engine again.