Help Please on Lightwin Carb issue?

[mercuryman]

Great tip on the screen Chinewalker, I have a 1966 Lightwin that is running lean. I went out and installed the screen and put it in a barrel, now there is no lag when you give it the gas.

[fleetwin]

How about the bowl vent, is that open?

[jerry]

Chuck…if you don’t find the solution, I think I have one that worked when I scrapped the motor…should be pretty cheap. Send me an email if interested and I’ll look for it….Jerry……………..studenut8@gmail.com….. P.S. leaving for a fishing trip on the 7th

[cajuncook1]

quote 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.

Seakaye, I had similar issue with a 1958 Evinrude 3hp I got on Ebay about 4 or 5 years ago. Good compression and ignition was all new and I could not get it to idle and run reliably. Frustrating!! I would fine adjust and it was run ok for a couple of minutes then start running rough again. Re-cleaned, the tank, fuel line, carburetor, and tank fuel filter, new carburetor kit…nothing. I decided to take a tiny light and remove the slow/high speed needles and inspect the orifices they reside. Come to find out it had a bugger up slow speed needle orifice, so I could never dial it in even with a new needle. Got a replacement carburetor from a donor 1959 Evinrude 3hp and all was perfect. 😎

Here is a video of my sweet "Ugly" nice running 1958 Evinrude 3hp. Had fun with it at Chicot State Park in Louisiana. I got it on Ebay for cheap because of the poor paint job.

https://www.youtube.com/watch?v=IoGNLlYPzRs

https://www.youtube.com/watch?v=2EDaZ5omLZk

[seakaye12]

quote fleetwin:

How about the bowl vent, is that open?

I’m not sure where that is. There are lead shots in various holes; I will have to look at other carbs to be sure but I think they should be plugged like that. Where is the bowl vent?

quote cajuncook1:

Your video on youtube….

Cajun; I had already seen that video and I thought at the time "wow; this is the answer"…So; I pulled the welch plug (again) and looked in there. The orifice looked fine to me; the tip of the needle was poking through…just like I assume it should. Same with the HS one; I see no problems there.

quote Jerry:

Chuck…if you don’t find the solution, I think I have one

Thanks Jerry. I might just do that. I am going to swap carbs again here (I have a few Lightwins) just to convince myself (again!) that it’s the carburetor. I’ll let you know.

[fleetwin]

Did the engine ever run well for you? Or, has it run this way ever since you have owned it. The compression seems OK, any signs of an internal water leak? You say that it ran pretty well with a different carb, why not just run it with that carb instead of getting another carb somewhere else?
The issue of RPM fluctuating up and down is peculiar, usually a messed up carb will just cause a lean/rich condition, not surging. The loose throttle shaft was a good thought though. The only other thing worth trying would be to set up an alternate fuel supply to eliminate the tank/filter/line/valve/tank vent as a cause.
Does it look like the intake manifold has been off before? If so, perhaps the gaskets are mixed up. Installing the outer gasket behind the reed plate will create a crankcase leak between the cylinders.
I can’t quite remember just where the bowl vent is but you can figure that out fairly easily. Remove the carb bowl, invert the carb body, then slowly inject gas/carb cleaner into the upper carb body cavity, the vent will make itself known quickly. Someone may have inadvertently plugged the carb vent with a lead shot/screw. Make sure there is nothing in the intake silencer or screen that might be blocking the vent hole as well.

[seakaye12]

quote fleetwin:

Did the engine ever run well for you? , any signs of an internal water leak? You say that it ran pretty well with a different carb, why not just run it with that carb instead of getting another carb somewhere else?

It was a basket-case motor when I got it free a couple of years age. Lots of salt corrosion; I had to pull the cylinder head and exhaust cover and spend a lot of time and effort getting the coolant passages open again. what a mess. I’m surprised it runs at all LOL! But; as you say…the compression is ok …

The water leak issue is I suppose a possibility; the exhaust cover has a broken off screw; there is no external leakage but I wonder if perhaps it is leaking into the exhaust port area? Does anyone know if that would cause speed variation?
The speed variation is most noticeable at medium to high speed. It actually idles fairly well….although the lowest speed happens with the mag lever between SLOW and START…..not over by SLOW like it should be…. (and yes; I have adjusted the mag-plate/throttle synch so it touches the lever when the throttle lever is between the dots….)

As for needing another carb; I have an equal number of Lightwins and carbs. If I took a carb off another motor…then I would need one for that motor…..

[fleetwin]

OK, well a water leak is surely a possibility, considering one broken exhaust cover screw, depending on which screw is broken. The outer screws would cause an external water/exhaust leak, but having one of the inner screws broken might let water leak from the cooling passage into the exhaust cavity. Water leaking into a cylinder(s) would surely cause an RPM variation though. There may not be enough water to drop a cylinder completely like you might expect though. You might try running the engine at WOT for several minutes, then shut it down quickly. Pull the plugs and look for water droplets. These exhaust covers get pitted from salt water/exhaust as well, which might create a path for water leakage.
The good news here is that you say the engine idles well, is that correct? An engine that idles well usually has a powerhead that is in good shape, with no crankcase leaks, which makes my intake gasket suggestion a waste of time.
A restricted/plugged up fuel supply would surely cause the engine to hunt at high speeds though. I can’t remember if your engine has a copper or rubber fuel line. It would be fairly simple to make an alternate fuel supply if your engine has a rubber fuel line. Just rig up another fuel line connected to a little lawnmower tank (using premix not straight fuel from the lawnmower!). These engines are known for having plugged up filters, fuel valves, fuel cap air vents, and crud in the metal fuel lines, so it is worth ruling all this stuff out. You mention having other lightwins, you might just use a tank/valve/line/cap from one of your other engines instead of the lawnmower tank rig up I mentioned.

[mr-asa]

quote Tubs:

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

How do you remove that?

[seakaye12]

quote fleetwin:

OK, well a water leak is surely a possibility You might try running the engine at WOT for several minutes, then shut it down completely. Pull the plugs and look for water droplets. These exhaust covers get pitted from salt water/exhaust as well, which might create a path for water leakage. A restricted/plugged up fuel supply would surely cause the engine to hunt at high speeds though.

I guess I should re-visit the exhaust plate; I can swap it with a less corroded one if that turns out to be the case. Some of the work I’ve done was like two years ago….so it’s tough to remember exactly what it looked like. I have been thinking that the exhaust pressure would be greater than the water pressure….and therefore it would not leak water that way….but I guess I’m wrong about that.

I did exactly that with the sparkplugs yesterday; no water droplets that I can see…..but it still might be a possibility.

The fuel flow is not the issue; although the sintered metallic filter in the tank was a devil to clean. BTW….after trying carb cleaner and brake cleaner to no avail….I found that the "Simple Green" cleaner in warm water did a bang-up job! Lightwin folks take notice!

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