Cam chain replacement, now won't run

I just helped a friend put in a new timing chain in his '99 wr 400 and now we have a problem. It will start up and run w/ the choke in, but when you take it off it backfires bad and cuts out when you give it throttle and will not run. It was actually backfiring bad enough to blow flames out the exhaust. We first thought it had to be off time, but we checked everything and according to the book it is spot on. Is there anyway it would start and run if the timing was 180 degrees off? We don't know what else it could be. He took the carb off during the chain replacement to clean it out, but we are pretty sure it was put back together the same way it came off. Anybody have any ideas? We are stumped. :lol:

Any help is much appreciated.

Thanks, DW

I just helped a friend put in a new timing chain in his '99 wr 400 and now we have a problem. It will start up and run w/ the choke in, but when you take it off it backfires bad and cuts out when you give it throttle and will not run. It was actually backfiring bad enough to blow flames out the exhaust. We first thought it had to be off time, but we checked everything and according to the book it is spot on. Is there anyway it would start and run if the timing was 180 degrees off? We don't know what else it could be. He took the carb off during the chain replacement to clean it out, but we are pretty sure it was put back together the same way it came off. Anybody have any ideas? We are stumped. :lol:

Any help is much appreciated.

Thanks, DW

It could be a piece of dirt in the pilot jet or you have #12 installed incorrectly. http://216.37.204.206/wps/Yamaha_OEM/YamahaDB.asp?Type=13&A=226&B=10

Most likely the slide in the carb is installed backwards.:lol:

Thanks for the replies. We just discovered that the accel. pump is torn. We think this may be the problem but since no dealership around here carries any parts at all, we will have to wait until one comes in. Does this sound like an accel. pump problem?

Oh Yeah! If you give it throttle the ACC pump must work correctly or the bike will stall!:lol:

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