Need Help

[2wcp]

Hi, I've got a 1988 YZ250 that has just had a motor rebuild done. New rod, piston, gaskets, ect. The bike will start up without the expansion chamber installed on it and it sounds ok other than being loud, once I put the pipe on it, it just kicks and kicks over but doesn't try to fire. I tried to blow air through the pipe and it seems like it has flow. is there anything else that could be going on that i'm missing? If you need any other info let me know, but I need some help guys.

Thanks everybody.

[oldschoolzuk]

could be so much carbon in the pipe????????Try some castrol super clean and put a rubber cap on one end then pour some super clean into the pipe and shake it up let it sit for about 15 minutes then hose it out you will be amazed at how much black soot comes out of there.If the silencer is plugged take out the baffle and repack it with new insulation...Hope this helps

[oldschoolzuk]

Also be sure to put your spark plug cap back on....

[tecate/250r RiDeR]

welcome
where are you at in nv?

[2wcp]

I live in reno too.

Im getting spark, i'll try cleaning the expansion chamber out, and i've even tried it without the silencer on.same results.

[FPMXer]

Is the exhaust valve timed right and or installed right? Another way to clean out the pipe is to spray alot of carb cleaner into the pipe, let sit for a few minutes and add some fresh then using a aim-n-flame light it up and let it burn off. Make sure it's at the end of the driveway and not inside the garage. Try to start it with only the pipe on and leave the silencer off. If it still won't start then you know it's either the pipe or exhaust valve.

[fastman69]

Does it run right with the pipe off?
If so, leave it off. Weight reduction right there and more power.
You are looking at a 6:1 weight to power ratio going to a 5:1. Talk about a nice increase.