XR carb won't stall during adjustment?


Sep 23, 2000
I'm trying to adjust the carb on the kid's XR100R. The manual says to set the fuel screw at 2 5/8 turns out, start bike, turn fuel screw in until bike stalls, then back out 1 turn.
My problem is the bike doesn't stall. It keeps running with the screw all the way in.
I have installed a brand new needle jet kit (needle and the jet that is pressed into carb throat). The clip is in the middle (specified) position. All other jets are original and seem to be in good condition. Air filter is clean. Points are gapped per spec.
I adjusted the screw at 1 turn out and the bike starts and idles fine, but runs rich. Plug is black and sooty. Exhaust blows a puff of wispy (not dark) smoke when I rev it from idle.
What am I missing?
Any comments would be greatly appreciated!


Aug 22, 2000
You were right to replace the float acuator needle and seat. That would be the first thing I'd think of when you describe the symptoms you're experiencing. When you say the bike runs rich, is it rich all the time, or only at certain points on the throttle, or under a load?

If all the other jets are correct, start checking the airflow. Is the filter clean, is the exhaust clean and free of water, debris or holes?

If these check out, then it may not be fuel, it could be burning oil from sacked rings, or leaky valves.

As far as the fuel screw goes, I've never been able to make one of those completely kill a little bike when it was warmed up and the idle set high. Try dropping the idle a bit and see if you can kill it then.

You didn't mention what year the XR is, if it's a points model, have the points been changed recently?


Aug 8, 2000
That's the idle screw that you are adjusting I think. I found I had to set mine at 3 and 1/4 turns out, otherwise it idled way too high. Good luck with adjusting it. Oh yeah, to get it to stall the idle screw must be turned out, otherwise it just gets more gas and idles higher.
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