Running on two cylinder only

[tosn]

Help me find a cure!
My Zuzuki DT55 year about 1986-1988 running on two cylinders only, the one in the middle (no 2) will never more pick up under no-load an load conditions. One day the problem appeared suddenly without any close signs. Just after a short break in waterskiing we were able to proceed and then it suddenly occurred after starting (in connection) the engine.
Measures been taken ?
New plugs
Checking the spark, status OK
Swapping coils and wires between no 1 and no 2, no difference, the engine still bogging
Compression test -
cylinder no 1 9,1bar
cylinder no 2 8,7bar
cylinder no 3 9,4bar
Pumping the primer when it?s bogging, no difference
Etherspray, startgas direct in the carb, no difference, rather worse when affecting the healthy cylinders beside.

Next step in my plan is the carb, dismantled and clean.

Anyone who have better advice? I?ll really appreciate any suggestions!

Thanks

 

[deejaycee_2000]

Re: Running on two cylinder only

Welcome to iboats ..... so the problem remains on the middle cyl even if you swop the coils? ..... have you checked the reed valve on the middle cyl?

 

[tosn]

Re: Running on two cylinder only

Thanks for being a member,
I appreciate your recommentation so I have now dismantled the reed valve and checking for abnormal function but I can?t discover any thing explaining the root cause.
I have also dismantling the the reed valve from the upper cylinder for comparing them togehter. Each valve consist of two leafs and one of them have a visible opening (1 mm) on one of the valve blades due to the adjustment of the valve on the stopper, besides that I have notning to declare.
Next step I planning for shiftning valves between upper and middle cyl, have anyone other suggestion?

 

[deejaycee_2000]

Re: Running on two cylinder only

so the problem remains on the middle cyl even if you swop the coils around?

 

[tosn]

Re: Running on two cylinder only

Yes the broblem remain in spite of coil switching. But I have good news telling You, the problem have been solved, the engine is now running on all cylinders!
After I checked the reed valve I understand the function fault likely must be in the fuel system so I decided to dismantled the middle carb. Inside the carb it doesn?t looked pretty I will say. A clear corrosion on all Al-parts in the throttle house which lead to loosen Al-flags. The flags among ather things packed the jet main. After cleaning the parts in the carb the engine running as expected.

A following question is why the corrosion have taking place inside the throttle house? (see picture, can?t attached because of exceeding the forum's limit of 97.7KB)
Thanks for profitable discussion so far!

 

[deejaycee_2000]

Re: Running on two cylinder only

the corrosion can be caused by water in the carbs, always good to install a water seperator ....