Need Help Please

[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? I have also tried it with just the expansion pipe, and not the silencer attached. If you need any other info let me know, but I need some help guys.

Thanks everybody.

 

[CR 125 RMX 250]

Adjust the air mixture with the pipes on up and down see if it starts or runs

 

[whenfoxforks-ruled]

First, stop running the engine without the pipe! It is about the same as trying to start it without the carb. It is a very vital part of the 2 stroke package. Are there any dents or folds in the pipe? Has the motor been modified? Have you taken apart the carb? How are the reeds?