Pilot jet setting

I understand that but when I removed the old fuel mixture screw with no O-ring, spring or washer came out with it and when I put the new one in with a O-ring on the shaft and then thurn the screw out 2 turns and tried to start the bike all it would do is backfire and not run at all. I put the old one back in and it back fired once and started right up. That is what I don't understand. The only thing that I can think of is that the new screw is not the right one. I did notice that with the new one that when I seated it and then turned it 2 turns, it was real wobley and real loose.

Thanks for everybody's help.

What brands screw did you use? What screw was in before?

You do have it assembled like this: Screw-spring-washer-oring, right?

I do not know what brand the old is, but it is red and has a red knurled round knob with numbers 1-4 on it and has not O-ring. The new one is from haynes racing for fcr carbs, and it came with it's own Oring. I'm sorry but I have not had the chance to see if a Oring is stuck in the tunnel for the screw goes yet. So I don't know if it has a spring or a washer in it yet. will a oring if it is stuck in the shaft not allow the spring and washer to fall out?

The washer could stick to the O-ring, but the spring wouldn't. You'll need to clear the bore and be sure you have these three parts.


> Some after market screws have needle tips that vary in shape considerably from stock, and from other screws. If one worked and the other did not, compare the tips.

> There are two different length screws available for FCR's, depending on year and model. Compare the length of the two screws from the threaded portion to the tip.

There is evidently no reason, unless I missed something, for you to be changing this screw anyway. The old one worked, it simply needed the spring, washer and seal on it. Put it back together that way and send the new one back.

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