Jonsered 670 Champ carb screws backing out in use.

At least it's rich not lean! Any fixes that don't lock the screws in?

Are the springs under the screws

ancy said:

At least it's rich not lean! Any fixes that don't lock the screws in?

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Check the springs. Beyond that in my opinion it is best to replace the carb. The threaded holes for the needles get hogged out so that the needles will vibrate themselves loose. If you can move the needles up and down in the hole at one turn out then it is time to replace the carb. I have junked a bunch of those Tills this year.

Basically the needle boots get hard and shrink a bit. That messes with the spring tension and allows the needles to vibrate ruining the holes. Sometimes the springs themselves will be broken or worn thin.

Had one carb that the low turned out and the high turned.

Find a different carb if you can move the needles up/down and side to side. Not worth the effort to repair.

If you get a different carb then get a SOFT boot or do not install the boot, no sense in ruining another carb.

pull the jets out and use a thin piece of zippy tie in between the threads.. it will hold the screws in place