Post Number: 4
|Posted on Sunday, April 15, 2018 - 08:19 pm: ||
I have a 1955 Gray Marine 4-75 with a Zenith 63 M carburetor. It starts easily but I cannot get it to idle on a consistent basis. At times it will idle at 600-800 rpm but a few minutes later it revs up to 2000+ rpm and no adjustments have been made? When this happens, Adjusting the idle screw (turning it counter clockwise) will not decrease the rpms as it should but may actually increase the speed and it shortly after dies. Suggestions?
Post Number: 968
|Posted on Wednesday, April 25, 2018 - 08:27 pm: ||
It sounds like your throttle return spring isn't working right or at least the linkage to the throttle is somehow not returning to the idle position or there is too much play in the throttle linkage.
You might try removing the linkage to the throttle and force the throttle to idle position - then see how much play there is on the wire connecting to the throttle.
The throttle control should be fairly stiff.
Or - (worst case) the throttle plate inside the carb has somehow become loose and squirms around.
That means that you'll have to take the carb off the engine to inspect. Not a tough job - just a bit awkward - it works best if you hang yourself by the ankles from the roof rafters.
You may need to re-set the mixture - start with it about 1 1/8 to 1 1/4 turns from dead closed.