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I rebuilt the motor this past winter, hotrod crank, cam, 11:1 piston, stg2 cam, timing chain and both gears, exhaust rocker for the decompression and it's pin, starter, battery and cables. Jetted at #25 pilots, 3rd groove in dynojet needles, 2-1/2 turns on air screws and 165/170 mains. This seems a bit lean.

The motor will crank but it also backfire's in the exhaust before it starts. It will backfire 10-15 times then start and idle fine. If it's shut off and restarted it will fire right up, if it sits 5 minutes it will backfire a couple times and start, the longer it sits the more it backfire's.

Checked the valve clearance, it's OK.

Cam timing I though was OK but after rechecking it again I had to stop past the TDC mark to have the cam gear dimples even with the head. The crank mark needed to be between the center of the viewing hole and the edge. Moved the cam one tooth and the ingition mark aligned with the cam gear dimples. Had to test it, two back fires and it starts.

Anything?
 
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