Rough running/backfire/die PROBLEM SOLVED

[maxducati]

After working through the carbs and compression tests and manifold exhaust leaks the problem was solved adjusting the exhaust tappets. The manual suggest 0.12mm gap. There was hardly any play in the tappets so set them at between 0.15-0.20mm. It now idles perfectly and runs like a dream. Airscrew is set at 1 1/4 turn out. Advice was provided by a 2CV expert who suggested that with modern fuel and running in hot weather old 2CV's are now run with 0.25mm gaps whereas the manual suggests 0.20mm. Hope this helps others with the same problem.

[catteeclan]

A lot of vehicles hammer the valve seats and tighten the gaps. The only fix is good maintenance.
Well done.

[desertjoe]

just been through the same sh%$t! sitting on the east coast of africa with a XLR 250 1992. cannot find anything on them but assume mostly the same as the XR and XL?! just rebuilt almost everything and it is not idling 100%, then dies. also massively backfiring blue flames when decelerating. new piston, cam chain, valves etc etc, but set the valves according to the XR haynes at 0.1 in and 0.12 out? am at sea level, hot and high humidity. air screw now at 2 turns. gonna change the ex setting to .2 now and see what happens! any other advice lads? oh yes, just posted all this on africa twin forum for more details!

[maxducati]

Sorry just seen this......i have to be honest I only had a 0.2 feeler gauge. so i just kicked her over till the inlet valve was fully extended and set the exhaust to 0.2. Nothing very scientific i am afraid, but she runs well now. on the 600 the airscrew should be out 1 1/4 turns.

the only other thing i did was make sure all the hoses were tight and the airbox was fully open until she ran fine then, but the foam back in.

hope that helps