In the 1971 Thunderbolt, what was the pilot jet size?
My parts book does not list it.
"I've got the Ethanol Blues"
So I been broken for about two weeks with a mending hand. Today i decide to kick the bikes to life. The BMW cranks up and runs idling just fine. I have a hell of a time starting the Thunderbolt and then even after it gets going it doesn't want to idle. So this gets me thinking (can I put a Bing on the Thunderbolt) what is the difference. Cause the Beemer has been sitting for three weeks and the BSA only for two.
I think the difference is that the Bing jets are sitting down in fluid not getting gummed up while the pilot jet on the AMAL is high up out of the fluid where it gets gummed by drying fuel.
So first chance I get I'm going to drill out that pilot jet and screw in one on the bottom of the carb body. It will still be high up but at least I can get to it to clean it.
Or put an pilot jet in the bottom of the float bowl...hmmmmm.
Last edited by Semper Gumby; 05/16/138:03 pm.
Gaggle of BSAs a Honda an old BMW and a Montesa Parking lot Elf in training
If you drill the pressed in pilot jet,you would need a 20cc screw-in pilot jet.The bike would idle better if you don't drill the pilot jet but just clean it with a 0.016" wire,#78 drill,or 0.4 mm drill. The difference in idling quality isn't huge.
You dont need a longer drill bit--just stick the normal length drill bit into a piece of the flexible tube supplied with cans of WD40. Then then you are sure that you have the drill bit through the pilot jet apply a small piece of tape such as masking tape in line with the outside of the carb body. Then next time you will know when you are correctly through the pilot jet----=when the edge of the tape lines up with the outside of the carb body. HTH