Ok, as a disclaimer, this is my first bike. I'm fairly mechanical and I have a bike person to help me out on this little project.

Just picked it up on Sunday and we've cleaned the carbs and lines (a nice 2 inch clog of crud in the fuel line), changed the gas and got it running with the kick start (starter chain won't stay on). However it backfires. Pretty sure it's because of the lack of an exhaust gasket. Is there something I can use as a quick fix to seal that up until I can get the gasket ordered? I really want to get this bike moving better so we can see what else it needs. Is there another reason for the backfiring? Everything else runs smooth and it starts right up with good compression. It only seems to backfire at a higher rpm.

hello,

the chances are you have the timing set wrong, the xs250/400 are terrible for needing acurate timing and I have had many problems from the timing on my 250se being just slightly out, set the timing by ear, not by strobes because it never works on these bikes. Could also be that the carb inlet manifolds are split, new ones are easy to get and are cheap on www.ebay.com with little postage to the uk.

good luck

richard