Help Please on Lightwin Carb issue?

[seakaye12]

I have a 1964 Lightwin Evinrude that I have been having an on-going "hard-time" to get to run well. It’s got 75/80 PSI, all new ignition and a completely gone thru carburetor. New float; all the kit components (boss gasket) etc have been replaced. More than once lol….

What am I missing?

It runs "ok" ….but not the way it should. The rpm’s vary up and down…and it is NOT dropping a cylinder. It won’t idle down like it should. It seems to sometimes run rich…and other times it seems to run lean.

If I hadn’t already replaced the float and needle/seat…..I would suspect that the fuel level in the bowl varies…..but I check and re-check things related to that…and find everything ok. Obviously I am missing something.

Any hints?

Chuck

PS: The carburetor that is on it has the low speed and high speed needles. I know it shouldn’t have that on a 64….. but I can’t see any reason that it would make things worse. If anything…it should make them better?

[chris-p]

I guess the first question is, what carb is on it exactly?

[seakaye12]

It has the original 1964 carburetor but the bowl half was swapped with one from a 1957 3 HP. That’s why it has the two needles.

I originally ran it with the original bowl (fixed jet) and it ran the same with that one. I assumed (perhaps incorrectly) that the fixed jet had been messed up due to improper cleaning which might have enlarged it…

[chris-p]

I wonder if the surging is an air leak.

Check the carb welch plugs, the throttle shaft, the crank seams, things like that?

[fleetwin]

Nozzle gasket OK? Did it run the same way with the original bowl/fixed high speed jet?

[seakaye12]

I can see no discernible play at the throttle shaft. At one point I dabbed heavy grease around the crankcase joint…no change. The nozzle (boss) gasket is new; the genuine OMC version that comes in the kit 439071.

It did run the same way with the original bowl; I was sooooo sure that replacing the lower half would solve the problem.

I did swap the entire carb with another one…and that made a huge difference…..so I feel that the issue is definitely in the carb somewhere.

PS: It also starts hard. Sometimes requires the choke even when warm; other times it seems essentially flooded.

[The Boat House]

Was removing this plug to clean these
passages part of your carb rebuild?
Should be a new one in you rebuild kit.

[kevinrude]

check the throttle cam follower — they sometimes get stuck in the full advance position when you throttle down — grease it up good and make sure that the spring actually pulls the thing back when throttling down

[chinewalker]

Is the screen between the air horn and the carb mouth? It was explained to me by a 40-year OMC tech that it needs to be there to run properly as it creates a rich condition akin to partial choke.

[seakaye12]

Yes I did pull the welch plug when I rebuilt. And; the screen is there.

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