Miss or rough running when cold

Minn-Tex Lee

Minn-Tex Lee

Senior Member
I have a miss or rough running engine when cold. This just showed up. I have 1200 miles on the rebuilt engine. The GAV is at 1/4 ccw. Changing it makes no difference. I changed the plugs. No difference. I start full retard and run 3/4 advance.
The problem seems to go away after 4 miles.
Could it be a stuck intake valve? How much trouble is that to fix?
Any thoughts on this would be appreciated.
Lee
 
What you describe is actually pretty normal for a cold engine, until it warms up, but it usually clears up by opening the GAV a bit when cold.

1. Make sure turning the GAV knob is really turning the GAV on the carb. Repro choke rods have the knob screwed on and it is possible to turn the knob without actually turning the GAV.

2. It could be a blocked passage. Take the carb off and apart, open the GAV a lot, spray through each jet backwards with spray carb cleaner, follow that with compressed air. Then put it all back together and test.
 
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