300/440/550 1986 js550

[Rushford_Ripper]

I have a '86 js550 that I bought all built up. The ski ran great and then one day while riding, she quite on the top end. I did everything possible to figure out the problem but at a loss. She will start fine, run but as soon as the throttle is wide open it dies. I went through the entire fuel system and no luck. I changed the carb, filter, release valve, and fresh gas. I did notice that the exhaust manifold gasket has a leak at the top. Could that be the problem? Someone told me it could be the coil? I don't know. I have the gasket, just need to put it on but I can't tell if it will help without running it at max throttle. Any ideas? Anyone in the western NY area that would want to fix this thing up for me? For aftermarket parts it has a jetsport high comp. head, coffman half pipe, jetsport air cleaner, and a stock waterbox. Thats all the motor work. Any info will greatly be appreciated.

 

[Pro-pulsion]

My ski is going through the same problem. I can start it and let it idle all day...soon as I put some load on the engine it snuffs out like hitting the kill switch. I too put a new carb on and no change but I did notice that the ski is virtually non-responsive to carb adjustments. So my thoughts are that I need to replace the crank seals, possibly the bearings too. If there is too much play in the bearings the crank will move enough to stretch the crank seals and open a small air gap.

I have the new seals but have to wait until spring to prove my theory lol. If you have an exhaust leak, then yes it will starve the engine of air because it will fill the engine compartment up with exhaust faster than it can take in air. So you should get that one taken care of first before going any further. A coil will do that too but most commonly it will get to a certain temp before it starts to fail.

The only other area I have heard of that does this too is the high tension leads (spark plug wires). Sometimes they will deteriorate and get brittle inside the sheath and eventually fail. I've seen it happen on a newer couch once, when the real electrical requirement was there, they couldn't compete with the demand which in turn gave top end running issues.

 

[FlightPlanDan]

carb clean?
Knock out the simple stuff b4 you dig deep. If it was running good b4.....
How's compression?
Fix the exhaust leak even if it's not the cause of your current problem.

 

[Rushford_Ripper]

Compression is 150 or 155? in the cylinders. Carb is good to go, clean on both and both with new pumps. I was screaming on the lake and she died. Then it was a slow ride back to the dock because of the top end. So I am thinking its that gasket.

 

[Rushford_Ripper]

Could have been weak in the spot and blew out.

 

[FlightPlanDan]

How do the plugs look?
Just asking cause I went thru alot of head gaskets with my 550

 

[Rushford_Ripper]

I changed those too. Believe me this thing is a nightmare haha!

 

[john zigler]

an exhaust leak, of any kind will fill your eng compartment, with gasses, and "choke" your ski off. especially at WOT.

fix your exhaust leaks...

 

[jetski9010]

Fix the exhaust leak for sure. If the crank seals have not been changed in a while you minds will change them while its winter time. Also check your crank bearings as was stated before. If you have any questions about the electical system I would suggest just send your whole electical system to john at jet ski solutions to go over everything. A lot of these 80's jet skis are tired as they are but he can bring the system to above factory specs when it was new. http://www.jetskisolutions.com/p13_kawasaki_550650_electrical_box_recondition_service.html

 

[RenoJenkins]

Pro-pulsion: You probably would have noticed this when you changed carbs, but check for water in the gas. I know it sounds strange, but my ski acted the exact same way. Fortunately I noticed the milky colored watery gas, when I was checking the fuel system, before I tore into the motor any further.

 

[Rushford_Ripper]

Did your ski run fine out of the water?

 

[Pro-pulsion]

It seemed to idle fine out of the water and in it but it wouldn't respond to carb adjustments. I know there was no water in the fuel lines because i pulled the tank and cleaned it thoroughly, cleaned all the lines, by-passed the fuel valve and ran the reserve line direct but it still never cured it. The only time I noticed it would run right is if I started it with fogging oil, the oil would coat the base and wherever the air leak was and run fine. I could run it for a good half an hour until all the fogging oil cleared out and then it would act up. My first time ever out with it, it ran perfectly for a good hour and a half with just a little bottom end bog. After that it would run fine sometimes for 45 minutes then just shut down like I hit the stop switch, sometimes it would last 15 seconds before doing that. The only seals I didn't change because I thought they looked good were the crank seals. After fighting with the cylinders to get them off I started to think that my ski was never torn down so I'm probably still running on 17 year old crank seals.

 

[Rushford_Ripper]

Well I am going to fix the gasket, change the waterbox, and wait until spring rolls around so I can get out to test it. If it doesn't fix it then I will have to do the seals or buy a new ski HAHA. I have a back up '84 550 that I am in the process of building. That thing is more reliable then the '86. Everything is going to get done to that except a high compression head.