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20LG missing on #2 Cylinder

C

cleco

New member
Hello,

I have a 1989 20LG (6L3) engine that is basically band new and has sat for the last 25 years in a garage. I cleaned the carbs, cleaned the fuel tank, replaced the plugs, and then tried to start it. It runs, but very rough and drops the #2 cylinder and is missing. I swapped the coils around (the miss stayed on #2) I checked the timing, which was correct. I do not have a factory manual and would lie to get one so I can try and test the CDI unit.

Please Help.

Thanks.
 
25 years sitting in a garage? Perform a compression check on the cylinders. 25 years is a long time for lots of moisture to get into cylinders, create internal rust, and all gaskets/fuel lines to dry out/crack/fail. Check all fuel lines for cracks and perform a compression test to see if rust on cylinder walls damaged rings when you turned it over. NEVER RUN ETHANOL BLENDED GAS you buy at 99% of gas stations in the engine as it was manufactured prior to ethanol mandates. All gaskets, fuel lines and everything that comes in contact with fuel wasn't designed to deal with ethanol blended gas that will eat every line and gasket and gum up everything creating a total mess (including the gas tank if it is plastic and a 25-year old vintage tank - I assume it is a metal tank being that old though).
 
Last edited:
deepsea21 said:
25 years sitting in a garage? Perform a compression check on the cylinders. 25 years is a long time for lots of moisture to get into cylinders, create internal rust, and all gaskets/fuel lines to dry out/crack/fail. Check all fuel lines for cracks and perform a compression test to see if rust on cylinder walls damaged rings when you turned it over. NEVER RUN ETHANOL BLENDED GAS you buy at 99% of gas stations in the engine as it was manufactured prior to ethanol mandates. All gaskets, fuel lines and everything that comes in contact with fuel wasn't designed to deal with ethanol blended gas that will eat every line and gasket and gum up everything creating a total mess (including the gas tank if it is plastic and a 25-year old vintage tank - I assume it is a metal tank being that old though).
Click to expand...

Compression test done with 120 PSI in each cylinder. I am in Canada and don't have ethanol blended fuel.Thanks
 
Re: 20LG missing on #2 Cylinder UPDATE!!

I have a 1989 Yamaha 2 stroke 20 Hp that is misfiring. I got this engine from a lady who told me her grandfather bought it new, used it several times then passed away and it sat until now. Here is what I have done:

-Cleaned out tank and lines, changed fuel filter.
- installed new plugs (two sets)
-removed carbs cleaned them completely, they were not dirty at all.

Tried starting, ran, but a bit rough. Took it out for a run on my boat ran ok for 15 minutes and then dropped cylinder.#2 cylinder misfiring, pull that plug cap and engine hardly changes, but pull #1 plug cap and it dies immediately.

Since then:

-checked plug caps and wires, they are like new. Ohms check on caps OK
-swapped coils around and problem remained with #2 cylinder
- swapped out plugs
- tried different tank with known good one
- checked timing both #1 and #2 both good
- checked both coils with meter
- removed flywheel and inspected charge coil and trigger coils, again like new and checked with meter....ohms check.
- rebuilt fuel pump, no change.
- removed carbs and cleaned again.
- checked all wiring connections a good.
- removed flywheel and swapped trigger coils around, no change.


This leads me to believe that the CDI box may be buggered.

Please help
 
Re: 20LG missing on #2 Cylinder UPDATE!!

cleco said:
I have a 1989 Yamaha 2 stroke 20 Hp that is misfiring. I got this engine from a lady who told me her grandfather bought it new, used it several times then passed away and it sat until now. Here is what I have done:

-Cleaned out tank and lines, changed fuel filter.
- installed new plugs (two sets)
-removed carbs cleaned them completely, they were not dirty at all.

Tried starting, ran, but a bit rough. Took it out for a run on my boat ran ok for 15 minutes and then dropped cylinder.#2 cylinder misfiring, pull that plug cap and engine hardly changes, but pull #1 plug cap and it dies immediately.

Since then:

-checked plug caps and wires, they are like new. Ohms check on caps OK
-swapped coils around and problem remained with #2 cylinder
- swapped out plugs
- tried different tank with known good one
- checked timing both #1 and #2 both good
- checked both coils with meter
- removed flywheel and inspected charge coil and trigger coils, again like new and checked with meter....ohms check.
- rebuilt fuel pump, no change.
- removed carbs and cleaned again.
- checked all wiring connections a good.
- removed flywheel and swapped trigger coils around, no change.


This leads me to believe that the CDI box may be buggered.

Please help
Click to expand...

UPDATE: I replaced the CDI and the problem remains.

I got my used CDI and installed it, NO FIX, exact same symptom's as before, #2 cylinder still misfiring. I put the timing light on #2 and checked the timing mark on the flywheel and it was very erratic. So I removed the flywheel again to check and make sure I did not miss anything. While I had the flywheel off I noticed something strange.
The flywheel has TWO small round trigger magnets of the inner shaft, one above the other, also the pulser coils have two pick ups on each coil. One of the magnets on the flywheel is NOT magnetic anymore!!
I have never seen this kind of set up before. Everything I have deal with in the past has had only one trigger magnet and the trigger coils have had only one post on them. Has anybody seen this kind of setup before?

ANYBODY?
 
Re: 20LG missing on #2 Cylinder UPDATE!!

cleco said:
UPDATE: I replaced the CDI and the problem remains.

I got my used CDI and installed it, NO FIX, exact same symptom's as before, #2 cylinder still misfiring. I put the timing light on #2 and checked the timing mark on the flywheel and it was very erratic. So I removed the flywheel again to check and make sure I did not miss anything. While I had the flywheel off I noticed something strange.
The flywheel has TWO small round trigger magnets of the inner shaft, one above the other, also the pulser coils have two pick ups on each coil. One of the magnets on the flywheel is NOT magnetic anymore!!
I have never seen this kind of set up before. Everything I have deal with in the past has had only one trigger magnet and the trigger coils have had only one post on them. Has anybody seen this kind of setup before?

ANYBODY?
Click to expand...
hello there i have the same motor and problem... did you find a solution
 
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