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  1. #1

    1200 NPV SUV cylinder 1 dying, RIVA F/A?

    I have been running this 2001 SUV motor for about 10 hours with perfect compression results each time. Swapped the stock fa for the RIVA round singles that came off a 99 gp1200 npv but didnt swap the carbs. The jets in the 99 were exactly the same and high and low speed adjustors were set to stock on the 99 just like the SUV carbs. The suv carbs were just rebuilt with oem kits, popoff adjusted to 55psi and pressure tested. All gaskets are new and in place. I also took the ski off of premix and put the oil pump back on. I could see oil dripping under RPMs out each RIVA collar and had cleaned the li es and the check valves by injecting WD40 through them before install. Primed the pump and lines b4 firing it up.

    The ski ran well for about 5 miles and then I could tell I was losing a piston. The front cylinder has low compression and not sure about the middle because I heard a clank when testing the front and didnt want to punch more holes in the block (if it already did?).

    We'll see what it looks like when I pull the head later this week. Motor pulled last night outside by flashlight...what a painful hour!

    I guess the question I have is this...

    Since both skis had the exact same carbs, jets and settings before swapping the FA, why would one burn hotter (if that turns out to be the case?) Everything appeared to be an even swap. Maybe just coincidence? I'll upload pics. I suspect the oil pump or the check valve for the front oil line but who knows?


  2. #2

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    If you have a fuel supply problem, as in a bad fuel selector switch, kinked or damaged line, a piece of debris partially clogging a N/S or jet, then you can have a lean cyl, also you may have a crank seal going bad. Doubtful on the oil pump check valve. Need to see pics before speculating more.

  3. #3
    Something that I neglected to mention that may or may not be important. For the last 2 hours of riding or so it has been an unusually hard start after sitting for 30 minutes or so while fishing. Also...when cranking it, now and then it would "sneeze' when trying to kick over. Literally, it sounded like one of those weak girl-type sneezes with a very slight lurch forward when it happened. It could also be described as almost a pressure relief sound like vvvzzzzzzzzzziiiii if you were to be able to sound that out quickly

    It happened a couple times when going from idle to trying to open up the throttle as well 10 minutes before it fried on me. For what it is worth, I always mash the throttle when I'm cranking it over to start it and then let it go quickly when it fires. I assssuuuumed this was some sort of a backfire due to being overloaded with fuel; however, it was not a bang sound at all.

  4. #4

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    did you jet the carbs or just put the flame arrestors on? if you didnt rejet it could have been pretty lean.

  5. #5
    I did not rejet the carbs. The 99 gp 1200 that I took them off of had the exact same jetting inside the carbs and the exact same hi and low speed adjustments as stock. They even had stock pop off pressure. I just removed the flywheel and all of the oil seals are intact. I inserted 10psi into the motor through one of the pulse line nipples after blocking off the carburetor intake manifold and the muffler. I sprayed down the entiremotor with Windex as well as the oil seals and spark plug base. no leaks anywhere.I ran out of time but will have a chance to pull the head tomorrowClick image for larger version. 

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    Last edited by macGruber; 10-02-2014 at 11:48 AM.

  6. #6
    at this point I am highly suspicious that of course it was the lack of rejetting regardless what the other carburetor rack was set at.I will check again by inserting 15 psi into the motor to do a leak down test tomorrow before pulling the head. If I do not find any air leaks does it make sense that if this was a lean condition due to the wrong jetting, I should expect to find the exhaust side of thefront piston starting to become eaten away?I would assume that since it is the last carburetor to receive gasthat it would suffer first?

  7. #7

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    That little "sneeze" is the infamous dead cylinder cranking over. As a rule of thumb you usually reset when installing aftermarket F/A's. I think there is a thread on here about proper jetting for those motors. Run a search. Sounds like a good winter project. Also, the SUV hull needs more power to be pushed through the water....I would think it would need more fuel....I.E. more jetting.

  8. #8

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    I would carefully check the fuel system , but we need to see pictures of the cyl and piston before really being able to trouble shoot this failure any further. The Non-power valve motors were not so sensitive to adding flame arrestors without rejetting, but the SUV may be closer to the edge on jetting due to the extra load.

  9. #9

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    Your comment about the SUV being harder to push thru the water brings up a curious tidbit of info:
    XLT's came stock with 87.5 pilots/117.5 mains where as GPR's with the same engine came with 95 pilots/117.5 mains.
    Weird huh?

    Quote Originally Posted by butterbean_29512 View Post
    That little "sneeze" is the infamous dead cylinder cranking over. As a rule of thumb you usually reset when installing aftermarket F/A's. I think there is a thread on here about proper jetting for those motors. Run a search. Sounds like a good winter project. Also, the SUV hull needs more power to be pushed through the water....I would think it would need more fuel....I.E. more jetting.

  10. #10
    Attachment 343257
    Attachment 343253


    Mystery solved. Boudin nailed it in an offline conversation. It was the front rod bearing. In fact, all of the rod bearings have quite a bit of play compared to 2 other cranks that I have on hand. The front was nearly siezed with debris. It really pays to shut these things down when they act up because the case halves just have minor rubbing and the cylinders will easily hoan out with a flex hone.

    About the re-jetting. That makes a ton of sense and would easily explain why the much much lighter gp1200 can get away with the lighter jetting with the aftermarket FAs. I'll switch them over to Osidebills recipe for success jetting. Here is a vid of the rod freeplay.


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