Evinrude Lightwin problems

[ausob-collector]

Well, I am completely stumped now. After the reed valves have been cleane and reset and all the other things I have done to this motor, you would think that it would run well. But it still has the same problem as it did before – it would run on one cylinder until I turned the fuel off at the tap, and then as it runs out of fuel the second cylinder picks up and it runs beautifully until it runs out of gas.
Carburetor is spotless, compression is great, ignition is fine, it’s getting enough fuel, what else can it be? No crankcase seals so that ain’t the problem.

Cheers
BP

[cajuncook1]

Have you isolated which cylinder is dropping? If so, which one?

Have you performed a cinder drop test?

While running, remove the spark plug wire to the top cylinder. If the motor continues to run then the bottom cylinder is firing and get enough fuel. If it dies, then your bottom cylinder is suspect. Replace the spark plug to the top cylinder nice and snug. While it is still running remove the spark plug wire to the bottom cylinder. If the motor continues to run then the top cylinder is firing and get enough fuel. If it dies, then your top cylinder is suspect.

If both cylinders pass the cylinder drop test, then your focus is now on fuel delivery.

There was a poster about a year back with a 1966 Evinrude 18hp that had very similar issues that you are having now. It took a year of on and off testing to get his motor right. Both his cylinders pasted the cylinder drop test but did not run well past mid throttle and would run rich or like on one cylinder. His motor would run all day long idling and start very easily. When he would run past mid throttle it would bog down and then, as instructed, he unplug the gas line like to run the carb dry. The engine would smooth out and run great for a few seconds.

Even though his carburetor was set correctly and totally clean it still ran very poorly above mid throttle. Replaced the fixed jet office with a new one and it ran perfectly. It seems the fixed jet may have gotten reemed or damaged along the way. That jet is metered precisely and if it is cleaned and the hole is enlarged, then a rich running condition can result. $5.00 for that little part.

The only thing that is different here is the gasket for reeds was found to be damaged and you stated the reeds were fouled and possibly not functioning correctly.

Just to make sure, are you running the motor on the gravity fuel tank above and not off a fuel pump from an external tank.

[ausob-collector]

CajunCook1, I have done a drop test and it was running so slowly it stopped when I took the plug cap off of either cylinder. Before the reeds were taken off and cleaned, the bottom cylinder wasn’t working but I could feel the jolt of the spark when holding the boot in my pliers while it was running on the top cylinder, which is why I thought the reeds weren’t getting any fuel to that cylinder.
I am running the motor off the gravity feed fuel tank, not an external tank.
It is getting plenty of fuel as I cleaned tank and fuel tap and filter.

Thanks again
BP

[cajuncook1]

quote AusOB_Collector:

CajunCook1, I have done a drop test and it was running so slowly it stopped when I took the plug cap off of either cylinder. Before the reeds were taken off and cleaned, the bottom cylinder wasn’t working but I could feel the jolt of the spark when holding the boot in my pliers while it was running on the top cylinder, which is why I thought the reeds weren’t getting any fuel to that cylinder.
I am running the motor off the gravity feed fuel tank, not an external tank.
It is getting plenty of fuel as I cleaned tank and fuel tap and filter.

Thanks again
BP

After you have run the motor a couple minutes and then turned off the motor by quickly retarding the throttle to off, have you examined the spark plugs? Does the top cylinder spark plug one look dry brownish gray and the bottom cylinder one look wet and dark?

Before you put the reeds back on, did you notice if they were completely flat against the mounting surface?

[ausob-collector]

I will check the spark plugs when I am back, I’m going away for a week.
The reeds are lined perfectly with the plate, they were completely flat against the plate as well.
Still very confusing huh?

Cheers
BP

[fleetwin]

Yes, very confusing indeed.
I just want to mention something about a test you recently performed. You mentioned that the engine picked up RPM as it ran out of gas with the fuel valve off. You concluded that the fuel system is somehow flooding just one cylinder and the affected cylinder begins to fire again as the fuel runs out which resolves the flooding problem.
Perhaps this is the case, but I am going to doubt your conclusion a bit. It is normal for most engines to pick up RPM as they run out of fuel as the fuel system/crankcase leans out. So, I just don’t want you to go down a bad path based on your conclusion. Indeed, you conclusion may be possible, but unlikely. Again, you have stated that your engine does NOT have an auxiliary tank/fuel pump set up. Your theory would have more validity if your engine had a leaky fuel pump that was flooding just one cylinder. I suppose the engine could have a primary/crankcase compression problem that could create a rich condition on just one cylinder, but this is unlikely, and you have mentioned that your compression gage readings are good.
I will spend some time re-reading your posts, but I fear we are missing something basic here.

[johnyrude200]

Fleetwin…remember my 6hp carb earlier in the year we looked at together at the meet?

I had a 6hp that would bog down at anything above idle…basically running way too rich. Make sure somebody didn’t plug up one of the air vents in your carb. With mine, it happened to be the high-speed air vent. I unplug the fuel line and let it run out of gas and it would run totally fine at all ranges for a second or two before dying off.

Your carb could have the low-speed air vent blocked. Make sure it isn’t plugged up – this would lead to a flooding at low speed, yet your high speed is working OK…right? The only way I figured it out with mine was holding another 6hp carb next to the suspect one, somebody had put a lead shot over one of the vent holes and plugged it inadvertently.

You might want to fish a thin wire down those holes and make sure they’re not plugged…just don’t put one down the orifice holes and ruin either the low or high speed orifice!

[fleetwin]

quote johnyrude200:

Fleetwin…remember my 6hp carb earlier in the year we looked at together at the meet?

I had a 6hp that would bog down at anything above idle…basically running way too rich. Make sure somebody didn’t plug up one of the air vents in your carb. With mine, it happened to be the high-speed air vent. I unplug the fuel line and let it run out of gas and it would run totally fine at all ranges for a second or two before dying off.

Your carb could have the low-speed air vent blocked. Make sure it isn’t plugged up – this would lead to a flooding at low speed, yet your high speed is working OK…right? The only way I figured it out with mine was holding another 6hp carb next to the suspect one, somebody had put a lead shot over one of the vent holes and plugged it inadvertently.

You might want to fish a thin wire down those holes and make sure they’re not plugged…just don’t put one down the orifice holes and ruin either the low or high speed orifice!

Joel
Sure do remember your carb, glad we stumbled on that problem!
In any event, I agree that a flooding engine surely picks up RPM as the carb runs out of gas. But, in this case the poster feels the engine is running on one cylinder and somehow flooding the other cylinder, he goes on to report that RPM comes up/other cylinder kicks in, as the carb runs out of fuel. To me, it is very unlikely that a flooding carb would affect just one cylinder, and that is why I am questioning this theory.

[johnyrude200]

yeah something sounds a little fishy here…

[ausob-collector]

Well, I have been thinking and would like to agree with you on that something strange is happening… When I just had the motor running I pulled off the plug lead for the bottom cylinder (while it was at its max speed right now, a medium idle) and the motor stopped running almost immeadiately. Then I restarted it and pulled the lead off the top cylinder and again, it stopped almost immeadiately, so now I am thinking that one clinger isn’t getting more fuel than the other but the high speed part of the carbie is blocked (or something along those lines).
It has been apart and cleaned and a new carbie it put in it though, so maybe it is just the carbie on it, so I’ll try and borrow another lightwin carbie and try it with that on.
In the meantime, I’ll keep experimenting and thinking about what’s wrong with it.

And johnyrude, it is the high speed range that doesn’t work, not the low speed.

Cheers and thanks again
BP

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