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Discussion Starter #1
First off, let me just say one word...UGHALKFLALKDHA

That's better.

Long story short - 90' JS550 with a milled head. Great compression (~150 in both). The ski has been sitting for 2 years in a garage since the last start up.

I replaced all hoses and lines, new battery and drained all the old fuel. Then I started on my journey.

I have been able to get the ski to run but it will not idle even with carb adjustment. As long as I keep giving it gas it revs out just fine. It's also really picky about when it wants to start. I'm getting plenty of fuel. My spark seems to be a good blueish color. Here's the tricky part...

I fired the jet ski up and had a friend throttle it. I removed the rear plug wire and the ski seemed to run exactly the same - same sound and didn't even seem to be missing. I put the rear plug wire back on and removed the front - it started missing.

It seems like the ski has been running on one cylinder the entire time since there was not a noticeable change after removing the rear plug wire. I'm thinking that's where my problem is. Any ideas on what to test? I know the CDI could be bad but wouldn't that affect both cylinders?
 

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First off, let ME say, ughalkflalkdha is not a word ;)
Yeah, take your plugs out, set them on the head, give it crank and look for spark on both plugs. I've bought plugs that have been bad, so try buying a couple new plugs. If your getting spark in both, let me know, I have a couple of ideas for you. What plugs are you running?
 

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Discussion Starter #3
I'm getting spark in both plugs. Appears to be fine - it may be a little weak but it should be plenty enough to fire.

I'm using NGK-R's.
 

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Do you have a spacer in between the plug and the head? When you mill the head you should put a spacer in between them, so the plug isn't either hitting your piston or about to be. Whatever its been milled, use that size spacer
 

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Discussion Starter #7
There doesn't appear to be a spacer. It does have a thicker copper gasket, though. There's also no sign of the piston contacting the plug.
 

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Try a couple different little spacer in there and see if that helps out by raising by the plug a bit. It may be that the fuel can't burn like it should if the plugs are too far down, and also check the gap on the plugs make sure they are the same and the correct gap. I know it seems dumb, but even new ones aren't alway's gapped right, or the same.
 

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Discussion Starter #9
Going to give that a try today. Keeping my fingers crossed...

Makes a little sense because it seemed to rev out fine but it would not idle...and the plugs would get pretty wet.
 

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Discussion Starter #10
Welp...no luck today. I am able to get the jet ski to run, just not idle. We've tried adjusting the carb but I can't seem to find a sweet spot. I'm pretty sure it's getting too much fuel and bogging out but I'm not certain.

I've also got a throttle issue. Every so often the throttle will get stuck wide open and I'm not sure if it's the throttle cable or something with the carb (we always seem to be adjusting when it happens). I'm now aware that my stop switch isn't working and I've came close to blowing the thing sky high. Definitely not getting in the water with this thing until that's figured out.
 

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Dumb question for you! Do you have it hooked up to the garden hose when your making your adjustments, or do you just try to make quick adjustments when it's dry? The reason I ask is because it will change from no water, to hose, and most noticeable on the lake with a full load under it. If your not far from the lake, I used to just go there and get it under a full load to tune mine. Fix your kill switch first though, lol. Have you gone back to stock settings and started from there, and how big of an adjustment do you make at one time?
 

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Discussion Starter #12
Yes, I have it hooked to a garden hose when making my adjustments.

I live near a lake so I could go there to make adjustments. I've wondered if having it under full load would make a difference. As for stock settings - we tried that and then started having trouble starting the ski. I suppose the milled head and higher compression would require different settings? I'm really starting to suspect a carb issue for the lack of idle and weird WOT issues.

Not sure if this is normal or not but when the ski got stuck wide open the second time we weren't making any carb adjustments (so we didn't know what to back off of to make it stop). After hitting the stop button a few times and not having any success I grabbed the plug wires and yanked them off. The thing continued to run for quite a bit longer! Maybe it's posessed...
 

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Did you rebuild the carb? I would try the lake myself. If the kill switch works, then take a screwdriver with you and A LOT of patience. Jetting -for me anyway- has always been a pain. I didn't have a trailer, so I just rode it around to see if was top or bottom end that needed the adjustment, then pull into shore make a a little tweek and do it again, and again, and again etc. You can also pull your jets and make sure the ends are not round out
 

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Discussion Starter #14
The carb hasn't been rebuilt. That's the only thing left that I can figure out. It seems to run fine while on the throttle but as soon as you let off it starts sputtering and dies.

I think I'll try and figure out my kill switch problem and then head to the lake. I may pick up a carb rebuild kit and try that just for the heck of it.

Thanks a ton for your help! I really appreciate it. I'll report back with what I figure out at the lake.
 

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Discussion Starter #15
After tinkering around a bit today, I found a few more culprits.




Does the 'low' mixture screw look a little more rounded than the 'high' screw? Is this significant enough to cause the ski to not idle?

Also - after reading around a bit last night I found out that when an engine revs high by itself it's usually a sign of an air leak in the carb. Is there a quick way to check that?
 

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As far as the jets go, I don't remember and I sold my 550. Not to be mean, but I won't take my new 800 apart to look at it for you. I'll ask around though and see what I can find. Let me know after your lake and carb rebuild.
 

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Discussion Starter #17
This thing is giving me one heck of a fit...

I rebuilt the carb and replaced the intake and insulator gaskets. If there was an air leak on the intake side it should be eliminated now.

I'm still at square one...no idle. I can get the ski to start and rev up fine but the idle adjustment does nothing. If I let off the throttle the ski will die. After that I have to pull the plugs and dry them off before it will start back.

So it's looking like I should be able to tamper with my pilot screw and get this thing to idle. Is there something I'm over looking?
 

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If the just won't idle now, there are two ways to fix that. Either on the throttle control, or the carb. The throttle should have an adjuster on it, just screw it outwards. Its the piece where the cable first goes into the throttle housing, or on the carb the crescent shape piece that the cable attaches to will have a little flat area on it, with a screw above it. It just screws in and tightens your free play in the cable
 

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Discussion Starter #19
Woo! I think I finally got it fixed!

Apparently the previous owner had the ski set up to not idle. I guess he was afraid the ski would get away from him on a spill.

After messing with the idle adjuster and about a half turn in on the pilot screw I was able to get it to idle. I'm running pretty rich right now but I should be able to get that lined out once I get this thing in the water.

Thanks for all of the help p10sdad!
 

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Discussion Starter #20
I spoke too soon...I still have a problem. I wish I could change the name of this thread since it's not an electrical issue.

I'm about 99.9999% positive my crank seals are bad. A quick google search gave me the following list of bad crank seal symptoms:

Hard starting - yep
Stalling at idle - yep
Engine "runaway" - BINGO

I should have known it was something more serious than an air leak after the unexplained runaway's. This thing revved out like an indy car. I held the kill switch for a good 5 seconds and it continued to run...I then yanked the plug wires off and no luck. Finally I was able to primer it a few times and flood it out. Scared the crap out of me.

This has definitely been a learning experience. I get to split the case tomorrow...yay! :|
 
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