ns90a dead cylinder

[thebobbykey]

I need some help . I've got a 1992 ns90a with a dead #1 cylinder ( top cylinder ) .I can pull the plug wire and there is no change in the motor, but the other two cylinders have a very noticeable change.

The compression on #1 = 135 psi , #2 = 133 psi , #3 = 134 psi .

If I get the plug boot close to the plug the spark will jump out and hit the plug ( so ive got spark ).

I've swapped out the #2 coil to the #1 cylinder still dead.

The plug has gs on it when I take it out ( so Ive got gas )

I've got new plugs and cleaned the carbs.

What else can it be?

 

[Sea Rider]

Re: ns90a dead cylinder

If the CD has 3 individual cables that sends power to each coil, could be the CD ? If so, must electrically troubleshoot or swap a used one in opt state and check.

Happy Boating

 

[TOHATSU GURU]

Re: ns90a dead cylinder

If you have spark, if you have compression, that would leave....The fuel system. Due to the age of the engine you might want to consider how much money you are willing to put into the engine before you get in too deep.

 

[dtj]

Re: ns90a dead cylinder

I
If I get the plug boot close to the plug the spark will jump out and hit the plug ( so ive got spark ).

What else can it be?

Remove the no. 1 plug and attach the wire to the plug, hold the plug against the block to see if the plug itself actually sparks when the engine is turned over............Don

 

[thebobbykey]

Re: ns90a dead cylinder

If you have spark, if you have compression, that would leave....The fuel system. Due to the age of the engine you might want to consider how much money you are willing to put into the engine before you get in too deep.

I hope its not bad enough that I should just throw this motor in the trash and buy a brand spankin new one.

Remove the no. 1 plug and attach the wire to the plug, hold the plug against the block to see if the plug itself actually sparks when the engine is turned over............Don

I'll try this tomorrow



Do you think it could be getting to much gas?

 

[bighh7]

Re: ns90a dead cylinder

I had the same problem and ended up rebuilding the carbs , make sure you do it properly as they are very sensitive and need to be squeaky clean . I found it cheaper to replace the long metering jets than try to clean them .

 

[thebobbykey]

Re: ns90a dead cylinder

when I pull the plug wire the rpm's seem to go up

 

[pvanv]

Re: ns90a dead cylinder

I need some help . I've got a 1992 ns90a with a dead #1 cylinder ( top cylinder ) .I can pull the plug wire and there is no change in the motor, but the other two cylinders have a very noticeable change.

The compression on #1 = 135 psi , #2 = 133 psi , #3 = 134 psi .

If I get the plug boot close to the plug the spark will jump out and hit the plug ( so ive got spark ).

I've swapped out the #2 coil to the #1 cylinder still dead.

The plug has gs on it when I take it out ( so Ive got gas )

I've got new plugs and cleaned the carbs.

What else can it be?

What method did you use to clean the carbs?

 

[TOHATSU GURU]

Re: ns90a dead cylinder

You may have a twisted crank. Mark the flywheel teeth at top dead center for each of the pistons. Then count the number of teeth between the marks. If they vary you have a twisted crank.

 

[thebobbykey]

Re: ns90a dead cylinder

You may have a twisted crank. Mark the flywheel teeth at top dead center for each of the pistons. Then count the number of teeth between the marks. If they vary you have a twisted crank.

They all checked the same ,also while doing this I noticed there are marks on the top fly wheel plastic cover you can go by.

 

[TOHATSU GURU]

Re: ns90a dead cylinder

Your next step is to determine why the one cylinder isn't doing it's job. You have compression and spark so look at the carb back through the reeds.

 

[thebobbykey]

Re: ns90a dead cylinder

visually the reeds look good.

If I get my hand close to the bottom to carbs I can feel some suction and the motor starts reacting, but the top one has no suction. I can completely cover it with no change in the motor and when I remove my hand the throat is filled with gas

from looking at a 2 stroke animation on youtube . I could have good compression with no suction if something is wrong in the crankshaft area.Pleeeeease tell me Im wrong.

 

[TOHATSU GURU]

Re: ns90a dead cylinder

No suction indicates a mechanical issue on that cylinder...Time to take the engine apart, but on one that old, the cost of any repair will exceed the value of the engine.