Jbarker
Active Member
Part number is not 685. No digital display on box. Looks like an MSD box. I don’t think it’s a pig rich at idle. I have turned the idle screws so lean that it will barely run yet the problem persists. I have switched carburetors and the same problem persists.Is the part number 685 and does the box have digital display on the top, or does it look like an MSD box.
I doubt it’s the box, I’m just trying to determine what you have.
And it’s probably a bad exhaust valve or it’s pig rich at idle.
I initially thought maybe it was a sticky exhaust valve. Now this seems unlikely. It seems like an exhaust valve would be less likely to stick when the engine is hot as things heat up with aluminum heads. But the problem only occurs when the engine is hot. Valve is not sticking when engine is cold because leak down test was good.