Super Jet Ski ran great for a week..now its dead in the water...halp!

Ok so the problems never end with this damn thing.

Rode for a week worry free...was hitting hard and reliable, started up fine all the time and was overall fun for once. Towards the end of the last day it ran well I had a pretty hard crash off a 40' cruiser. Held onto the ski but as i have no idle screw it died before i got balanced and back on it. It started up fine but ran like it was almost out of gas...as i was almost out of gas when i left the beach I assumed it was that and head back and refilled it. 92 octane w/ quicksilver oil.

Ran like crap from there on out. Was bogging badly and had no pop to the throttle at all. Ran like I had fouled the plugs. So i swapped in new plugs. Same issue.

Dug a little deeper and found that my dry pipe coupler had split and I had a nasty exhaust leak. YAY! that would explain my symptoms...i just ripped that in the crash and its a easy fix. Replaced it annnnnnnd same issue.

In fact it got worse as after riding it for awhile trying to diagnose the issue it dropped down to one cylinder while riding.


Checked out rest of exhaust system...from what I can tell there are no other leaks.

Checked out water cooling and water injection system..from what I can tell there are no leaks.

Pulled the plugs one looked "normal" one was washed clean.

Pulled the flywheel to check on stator plate, was still tightened down secure.

Pulled the electrical to check for leaks and was still sealed up tight.

Pulled the carbs off and AH HA! the carb that feeds the cylinder that was having issues had the butterfly valve very loose. It would not always open all the way with the other carb and would stay closed in some cases. That HAS to be the issue.

Fixed it and while the ski did run better and on both cylinders it still ran with a bog the entire time. It would get up to an estimated 25mph but it would get there veeerrrrryyyy slowly and if I turned it would lose all power, harder the turn the bigger the loss of power...it would then slowly accelerate back up to its current max speed.

Screwed with the adjustment screws on the carbs a bit to see if i had tuned it with a minor exhaust leak and now that it was fixed the carbs were off...they were 1/2 a turn out to begin with..put them at 1 turn out and still same issue. One thing I did not do is close them which I guess I should have tried.

For the record the ski sounded great in the garage before I took it down to the water today. Revved fast and hard and sounded like it was fixed. However soon as it hit the water it was done.


Talked with a guy who knows his :):):):) and he said to check and make sure the holes on the popoff side of the carbs was not blocked as that could lead to similar issues. He also said to swap in a different CDI to make sure my EPIC system wasn't taking a crap on me.

I will check both those tonight if possible but open to any other suggestions.

I appreciate your help guys.
 
Ok so I tested the compression with a crappy Shucks gauge. I took both plugs out screwed the tester into one of the holes and got 60psi...repeated for the other cylinder and got 30psi.

Obviously horrible PSI...where do I go from here?
 
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Ok..pulled the head..here are the pics..head oring did have a 1/2" piece missing on the cyl that showed 60psi. Also the engine held compression..just had really low comp.

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Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
Hmm. Well ur correct there. Did u pull the jug and look down in the cases. Did u eat a ring? I don't see any gross piston damage to the piston domes and the head domes don't show any pitting from debris. Compression is achieved between the pistons/rings and the cylinder/head fitment. Spare orings r a must if those are the originals. Ur crash could have caused enough of a wiggle to shift the head (unlikely but possible) and shear a oring. If the head has any uneven spots u can start blowing rings that way too. I've seen guys use thread sealant or gasket maker goo to help orings seal.
 

Waternut

Customizing addict
Location
Macon, GA
No offense but based on your findings so far, I would have to say that your ski has been neglected for some time so don't rule anything out. You're right, the engine SHOULD still run properly even with a blown o-ring but the cooling will suffer. The compression may be affected by the blown o-rings but I'm guessing there is another culprit here. IMO, it should be your highest priority to figure out why the engine is putting out 30-60psi because one cylinder didn't have a blown o-ring. Is the battery charged fully? Are the battery cables getting hot after cranking? Are the battery cable connections flexible indicating a worn/loose cable end? When you were in the ebox, did you happen to check for loose/frayed wires? I assume you've checked the plugs for a decent spark by laying them on the head and watching them fire?

If the compression ends up being something silly, you might want to check or replace your fuel lines and pulse lines. They could be cracked or a hole could be worn in one of them. Might be worth pulling the waterbox, fuel tank, and one way valves on the tank to see if anything is jacked.
 

Waternut

Customizing addict
Location
Macon, GA
Also... Is this just the light or are these two ports gouged? If they're gouged, you might want to check the status of your rings and pistons.
 

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Crab

thanks darin...noswad!
Location
Seattle
also looking at the walls there is evidence of blow by, I would pull the cyl and do a complete inspection. Also get a good comp guage.
 

Cannibal

Tasty Human
Location
Summit Lake, WA
One thing to clarify, engines don't hold compression, your compression tester has a schrader valve in the end. That's what hold the compression in the tester.

That one cyl with the two ports that have something going on is also too clean. Me thinks you have had some water getting there and steam cleaned that piston. You said the compression o-rings were fine, so it might be a good idea to check for warped head or cracked liner.

Time to pull the cyl as suggested and take a look.
 
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Ok...tested with a different comp tester...this one from auto zone. 120/150psi - Better than before..but still not the 180ish it should be with a ada girdled head and 35cc domes. Going to replace orings on the pistons and check it again. Will report back.


As for the damage to the cylinder that was there when i installed it...with all the other issues i had he happened to have a spare 760 laying around. He said it should work fine for me till I can afford to buy a mint cylinder. And with all the other issues I have had to fix on this thing I have not had the money to buy a new cylinder.
 

Waternut

Customizing addict
Location
Macon, GA
It's not local enough for me to drive to. I always just order and wait. The difference is, you get 10 o-rings for less than the price of 2 from a jetski place.
 
K here are pistons... You can see the verticle marks on the pistons..but you can not feel any of them with your finger. Pistons feel just as smooth as when i put them in new.

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