I have a 1979 340 Drifter that I fixed up this past fall and winter. After putting it all back together I took it for a test run Superbowl Sunday to see that I put everything back together properly. All seemed OK, however I did not open the throttle wide open at that time.
Yesterday we got a nice six inches of snow so I took it out again. This time I opened it up all the way. It seem to run good until I got past 3/4 throttle, then it would bog down.
I tried adjusting the air screw on the carburetor but this didn't seem to make any difference. From what I read in the Service Manual, this air screw if primarily for idle adjustment and should be between 1/2 and 1 1/2 turns open.
Background on sled: This sled sat for about 15 years without running. I did not replace the crank seals. When I took the heads off, one of the cylinders had quite a bit more carbon buildup than the other.
QUESTIONS:
1. Would adjusting the needle valve clip be worth trying?
2. Should I do a compression check on the cylinders?
3. Should I just go ahead and replace the crank seals?