742B carburetor/ governor

[Russell]

In a recent post (742B timing marks) I described my experience in replacing the head gasket on my machine. Now that it is up and running, there is a serious problem with the carb and/ or governor. It starts OK, powers up, and idles, but sounds like it has water in the gas, or is running on 3 1/2 cykinders. The exhaust smells like the fuel mixture is too rich, but if it starts to lose power, choking it helps. During re-assembly I filed and gapped the points, installed new plugs, and timed it correctly. In my teardown, I did not remove the carb-left it bolted to the intake manifiold. The only part I touched was the throttle linkage from the governor, and when I re-installed it I believe it was just a matter of putting in the two small bolts--no adjustment. Also had to remove the air horn, but that is pretty straightforward. In my first examination after experiencing the poor running, I found the airhorn gasket improperly seated, but after correcting it, the engine did not run any better. Added dry gas-that didn't help. I did a compression check, and have 160, 135, 160, and 165. I don't think one cylinder being low would cause such a rough running situation. I am not inclined to start adjusting mixture screws, or rebuilding the carb since it ran perfectly before the head gasket issue. I strongly suspect I made an error during re-assembly, and hope someone out there can save me an expensive session with the dealer.

 

[Russell]

PS--this is a Mitsubishi engine

 

[Tazza]

PS--this is a Mitsubishi engine

That compression is rather low.... Is your valve clearance correct? I can't remember what the spec was, but i thought it was around 10% difference.

 

[rpw]

That compression is rather low.... Is your valve clearance correct? I can't remember what the spec was, but i thought it was around 10% difference.

I also agree that you have to low of compression on that cylinder. I wouldn't expect to see anything less than about 145. Either valves or you have rings bad on that cylinder. Good luck.