Engine stalls when decelerating

Help. My bike has started to stall when I decelerate, especially when I disengage the clutch to downshift at slow speeds. It starts easily and idles great while standing still. Acceleration is strong. But when I slow down nearly to a stop it stalls. If I leave the clutch engaged it sometimes backfires and restarts.

It developed this bad habit over the last 5-6 rides. I have changed nothing, except to adjust the pilot screw during the past 2 rides attemtpting to correct the problem. It seems to improve when I use a leaner setting on the pilot screw, but still stalls sometimes.

I'm running a '99 WR400 w/stock exhaust and cam timing, grey wire cut, throttle stop removed, air box cover removed.

Kinda sounds like the coil going bad. Or maybe something funky with the stator, like metal shavings? Have you checked your spark intensity? If it’s not up to par, you may want to check these two things.

Assuming the air filter is clean, another thought would be a plugged slow circuit in the carb. You may want to give it a good disassembly and cleaning.

Good luck.

Check your slide while your in there.

This is exactly how my bike performs when I forget to close the hot start button. Just a thought. :)

SMD makes a good point with the hot start. I had a similar problem with stalling while deccelerating and found it to be my decompression cable. Every time I would turn right at low RPMs the cable would push the decompression lever at the motor just enough to stall the motor. Just one more thimg to check. Mike

1. change your spark plug ...

2. clean your carb ...

then report back ...

Temporary fix would be to turn the idle up.

Thanks for the suggestions, everyone.

I replaced the spark plug and cleaned the air filter today. Gapped the plug at .028, adjusted the fuel mixture, and set the idle a little high. Stalling is minimized but not completely normal yet.

Also, tested coil and found resistance about twice as high as spec on both primary and secondary. I've ordered a coil and carb gaskets, etc.

I'll report back when I've got the carb cleaned and coil installed.

After another ride or two I figured out that the bike only stalls when I use the rear brake. I discovered a short in the brake switch, replaced it and the problem was resolved.

By this time I had also bought a new coil. I rechecked the resistance on my old coil after removing the spark plug cap from the lead and found it was as good as new. If anyone wants to buy my new one let me know. The dealer wouldn't take it back.

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