Tuning Backfile with 123

[Labman]

Hi all. Haven't posted here in a while. I have a 650CC engine in my '71 500F. I had issues with the stock distributor so I installed a 123. Car runs great now but after driving it for while, when I go to turn it off, there is a backfire through the exhaust. What is it from...timing too advanced or too retarded? Or something else altogether?

 

[Labman]

Hi all. Haven't posted here in a while. I have a 650CC engine in my '71 500F. I had issues with the stock distributor so I installed a 123. Car runs great now but after driving it for while, when I go to turn it off, there is a backfire through the exhaust. What is it from...timing too advanced or too retarded? Or something else altogether?

Subject should be Backfire not Backfile. Sorry!

 

[Labman]

Could it be tappet adjustment? Anyone know?

 

[FR85]

Could be wrong but I'd say too retarded, I have just come out the far side of backfiring when decelerating and advancing timing combined with a refurbished carb has transformed it. And yes, if valves aren't opening and closing at the right times fuel could be getting ignited within the exhaust.