i have several friends with yfzs.. varying in years and they all seem to have the same problem. when you crack the throttle off an idle they die!!! some of these are modded some are stock. they all run very well at all other throttle ranges. we have put the accelerator pump cover on a couple but it didnt really help much. jetting has helped the most. what have you done to yours to correct this. is there a fix? thanks for the help

 

no one has this problem????????

 

Personally, I've never had that problem. As long as I let her warm up, the only time it will die is due to user error. [img]i/expressions/face-icon-small-blush.gif[/img]

 

You need a smaller leak jet for your accelerator pump. Its a common problem on the YFZ450. Go to YFZ central forums, theres posts there about how to fix it and where to get the leak jet. Also, dont expect your dealer to know what your talking about, most of them dont even know what the leak jet is. After reading your ENTIRE post though, if the pump cover didnt fix it the leak jet might not either. Mine got much better when i switched to the GYTR jet needle, i used to have the JD needle and it had that problem bad.

 

Here's what was wrong with mine...........

There's a switch in the thumb throttle AND a switch in the carb throttle housing..........BOTH switches have to open OR close at the same time (i think it's part of, OR the T.O.R.S. system) Look at the switches and see what I'm talking about........
ALL I had to do is readjust the throttle cable and problem solved......[img]i/expressions/face-icon-small-smile.gif[/img]

 

I had the same problem and it was all jetting. Installed new exhaust pipe did that new jet then changed air filter system started all over. I took the bike down to a race shop here they put it on a dyno and fixed the jetting runs great now. It will stall if it is not warmed up. If you don't have a dyno keep changing the jets till you get the right match for the mods

GITRDUN
is right on track IMO