i recently purchased an 88 Kawasaki JS550. After owning it for a month or so, only once cylinder started firing. Casually, I replaced the plug, and even switched the plugs to test is the one misfiring was bad, but both coils and plugs fired outside the cylinder when grounded. Now everytime I ride, it'll run great for 5 mins, then starts misfiring on the same front cylinder. Considering it is a single carb, I canceled that problem because one cylinder is firing fine. My assumption is that the ignition coil has gone bad. After riding for 5 mins the coil heats up and stops responding. I would love any opinions or advice, because this part is extremely hard to find and expensive due to rarity. Also, if this is the problem, how hard of a fix would this be? I have found some used EBoxes I could use to replace either the coil or the entire thing, but like I said I would hate to purchase this and it not solve my problem. Thank you in advance! Also something to note, the compression is fine as well. Rings were replaced and compression tested fine
Plugs fine, but only one cylinder firing
- Thread starter BradyK
- Start date
BombThreat
'Diggity
- Location
- Johnstown, NY
I'd agree with your diagnosis of a bad coil .
OCD Solutions
Original, Clean and Dependable Solutions
- Location
- Rentz, GA
What happens if you swap the plug wires? Does the problem follow the wires or does it stay with the cylinder?
Unfortunately I was unable to test this due to the length of the rear cylinder wire. It was unable to reach the front cylinder. I tested the spark on both wires and they tested fine out of the cylinder, but this was when the engine was cold. At this moment I thought something was going on with the carb and flooding the cylinder, but if that were the case I assumed it would affect both cylinders considering it is a single carb. I then resorted to the ignition situation
OCD Solutions
Original, Clean and Dependable Solutions
- Location
- Rentz, GA
Too bad those coils are so elusive. 
Is there enough wire left on the back one to trim it back and crimp on a new end? Sometimes the wire breaks internally.
JSS offers a rebuild service on those as long as the coil is good and it's just a wire problem.
http://www.jetskisolutions.com/p83_...0_igniter_plug_cable_replacement_service.html
Is there enough wire left on the back one to trim it back and crimp on a new end? Sometimes the wire breaks internally.
JSS offers a rebuild service on those as long as the coil is good and it's just a wire problem.
http://www.jetskisolutions.com/p83_...0_igniter_plug_cable_replacement_service.html
Thank you very much. Unfortunately you're correct on how difficult the coils are to come across... My only other concern is why the wire would work for the first 5 mins then stop working. That's when I resorted to the coil because I am aware they might fail under high temperature, which would make sense riding it 5 mins and letting it heat up. Just a stressful situation I want to make sure I get right so I don't spend money on useless partsToo bad those coils are so elusive.
Is there enough wire left on the back one to trim it back and crimp on a new end? Sometimes the wire breaks internally.
JSS offers a rebuild service on those as long as the coil is good and it's just a wire problem.
http://www.jetskisolutions.com/p83_...0_igniter_plug_cable_replacement_service.html
OCD Solutions
Original, Clean and Dependable Solutions
- Location
- Rentz, GA
A spare coil is never a useless thing. Especially as they get harder and harder to find.
Thank you very much. I'll respond with an update as soon as I get what's needed
Replaced the entire electrical box, both plugs fire out of the cylinder but it is doing the same thing. My next thought is the rev limiter. The owner before me seemed to attempt to delete it, but I'm not sure if they did it correctly. I'm convinced it is flooding the carb causing the cylinder to misfire. Would really appreciate any other opinions towards the problem because this is the last resort. Thanks in advance
tntsuperjet
Tntperformance-engineering.com
- Location
- Georgetown ca
Coils are almost never the problem. When it isn't a consistent miss or run issue.
The stator is bad. Either the exc or pulse coil is going bad in the stator and not generating enough cap current for the coil to fire
Also you can get the spark plug wires out of the stock 550 coil.
The early models have solid copper core and the wires do get corroded inside.
Make sure you have either resister caps or resister plugs but do not run both.
Also when diognosing spark open the plug gap to .070-.090 this will better simulate how much spark energy needed to fire a spark plug under pressure.
A weak spark will fire a plug in ambiant pressure but add the 100+ psi compression and the spark energy needed to bridge the gap doubles.
The stator is bad. Either the exc or pulse coil is going bad in the stator and not generating enough cap current for the coil to fire
Also you can get the spark plug wires out of the stock 550 coil.
The early models have solid copper core and the wires do get corroded inside.
Make sure you have either resister caps or resister plugs but do not run both.
Also when diognosing spark open the plug gap to .070-.090 this will better simulate how much spark energy needed to fire a spark plug under pressure.
A weak spark will fire a plug in ambiant pressure but add the 100+ psi compression and the spark energy needed to bridge the gap doubles.
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My next aproach is to check the compression. The top nuts on the head might've loosened up over time on the side of that cylinder that is misfiring. I'll check that and post an updated after that. Unfortunately it is at the Lakehouse so I'll get to it next weekend. Please correct me if I'm wrong but without compression, it can't ignite
tntsuperjet
Tntperformance-engineering.com
- Location
- Georgetown ca
550 usually blow the base gasket first if the head comes loose. Unless it has copper base gaskets.
I'm really hoping that isn't the case, but we will soon find out I guess. All gaskets are almost brand new though, so I'm hoping for some reason the torque was off and I didn't tighten the head enough. Key word "hoping"
Well I checked the compression and there is 155 in both cylinders. I honestly have no idea what it could possibly be at this point. Pull the ski out of the water after riding it just before dark and checked for any exposed sparks and I couldn't find any. Then I checked the spark on the plugs and they sparked fine. Really taking any advice I can possibly receive. Thanks again!
tntsuperjet
Tntperformance-engineering.com
- Location
- Georgetown ca
Here the problem with looking at spark.
When the plug is in the head it takes 3 times the spark energy to bridge the gap as it does out of the head and not under pressure.
So if your going to check spark open the gap up to .100 or more. So at least your in a similar spark load to fire the gap.
But my take is the stair is bad and once it warms up it goes bad.
Either that or you have water getting in the motor.
Have you looked close for any water.
If you have an old stamped head pipe not a car head pipe they love to crack by the base internally and leak water into Cyl
When the plug is in the head it takes 3 times the spark energy to bridge the gap as it does out of the head and not under pressure.
So if your going to check spark open the gap up to .100 or more. So at least your in a similar spark load to fire the gap.
But my take is the stair is bad and once it warms up it goes bad.
Either that or you have water getting in the motor.
Have you looked close for any water.
If you have an old stamped head pipe not a car head pipe they love to crack by the base internally and leak water into Cyl
Well I finally found the solution. In all honestly the only reason I am posing this is if anyone has a similar problem because the solution is completely embarrassing. So the carb just needed tuning. The high end was unscrewed almost an entire rotation too much, so I screwed it clockwise just over a full rotation and it performs like a dream. Only reason I looked past it was because it was only flooding the front cylinder and it's a single carb, but that apparently wasn't the case. Thank you to everyone for the advice, but just a little carb tuning was all it needed!!