Weber Backfiring

[zrayr]

Originally Posted by James Stern

John,

I'm sorry I am not responding all that quickly. I was away for 2 weeks and didn't see your response. I got a 2nd set of idle jets (55) and main jets ....."

Jim

That seems way lean to me. I'd try 65 idle with a 100 or 110 idle jet holder and a 135 main jet ( at least, if not bigger)

It's a BIG HELP to get a decent wideband A/F meter, then you see exactly where the problem is. That will save you a lot of time. I use the AEM unit.

Z

[Gaz64]

Jim,

You have dropped your idle jet from 70 to 55 in one hit?

Way too much percentage change.

A 55 jet is 62% of a 70 jet.

Obviously a 70 was rich, a 55 is lean. A 60 to 65 is what you need for fuel.

So get a number drill set and drill your 55s to #74 and work up, until you find your driveability is acceptable, watch your A/F meter while tuning.