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  1. #1

    2017 GP1800 fresh rebuild running rough

    So I finally got my short block reassembled, head resurfaced, 4 valves replaced, pressure checked and all new gaskets throughout. Basically a brand new engine. Got it all together and started it tonight. It started right up but sounds rough. Almost like a knock of some sort that I can't exactly pin point where. Once water got to circulating it did quieten down a bit but still runing rough as in at idle the engine is shaking and the obvious rattling/knocking sound. I bought this ski used and completely apart in the bed of my truck so the supercharger, intercooler, clutch etc was all used before hand with 19hr total.

    Also at idle the two Jets out of the intercooler don't spray water.

    Just comparing this to another GP1800 I have which at idle runs smoothly and quiet without the engine shaking.

    Where do I start with troubleshooting? Mods are maptunerx stage 1 plus, Riva retainers, through the hull exhaust, ribbon delete, factory intercooler with riva air intake.

  2. #2
    Here's an idle video and pics that show the timing marks
    Click image for larger version. 

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    And a rev video that shows the noise goes away. I don't think I'm getting water throughout the block. It has a Riva block cooling kit so it may not be correct


  3. #3
    jetpilot785's Avatar
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    Usually when it idles rough but sounds decent higher in the rev range, that is typically a cam timing issue and if you're running stock cams with stock cam gears, the timing looks off on both marks so it could be too advanced on one and too retarded on another putting the LSA too close or too far apart. Another thing to look at is if the cams were switched and the exhaust is on the intake side and vice versa. Intake should have 6S5 on it and the exhaust should have 6ET. The cam gears are the same so I can see them getting switched up if not paying attention or keeping track of what side came off where. Get those marks dead center or as close as you can and it should run decent for you.

  4. #4
    Quote Originally Posted by jetpilot785 View Post
    Usually when it idles rough but sounds decent higher in the rev range, that is typically a cam timing issue and if you're running stock cams with stock cam gears, the timing looks off on both marks so it could be too advanced on one and too retarded on another putting the LSA too close or too far apart. Another thing to look at is if the cams were switched and the exhaust is on the intake side and vice versa. Intake should have 6S5 on it and the exhaust should have 6ET. The cam gears are the same so I can see them getting switched up if not paying attention or keeping track of what side came off where. Get those marks dead center or as close as you can and it should run decent for you.
    Yeah stock cams/gears. The exhaust side has the purple mark so should be correct. I thought maybe it was out but it's so close it looks spot on. I was having to bump it over using the starter so got it as close as I could for a picture

  5. #5
    Cam timing is very important, but a simple check would be to install new plugs no matter what they look like, I’ve seen new looking plugs be fouled and cause rough idle

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  7. #6
    Quote Originally Posted by snipe243 View Post
    Cam timing is very important, but a simple check would be to install new plugs no matter what they look like, I’ve seen new looking plugs be fouled and cause rough idle
    Im going to re adjust timing in an hr or so. The plugs are new out of the box. This is the first time they have been used.

  8. #7
    xkon's Avatar
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    Quote Originally Posted by Z'mnypit View Post
    So I finally got my short block reassembled, head resurfaced, 4 valves replaced, pressure checked and all new gaskets throughout. Basically a brand new engine. Got it all together and started it tonight. It started right up but sounds rough. Almost like a knock of some sort that I can't exactly pin point where. Once water got to circulating it did quieten down a bit but still runing rough as in at idle the engine is shaking and the obvious rattling/knocking sound. I bought this ski used and completely apart in the bed of my truck so the supercharger, intercooler, clutch etc was all used before hand with 19hr total.

    Also at idle the two Jets out of the intercooler don't spray water.


    Just comparing this to another GP1800 I have which at idle runs smoothly and quiet without the engine shaking.

    Where do I start with troubleshooting? Mods are maptunerx stage 1 plus, Riva retainers, through the hull exhaust, ribbon delete, factory intercooler with riva air intake.
    If a dedicated line was added from the pump to feed the intercooler, you will not have water pissing out the intercooler side when running on the hose which probably would be the case if you have the engine block anode cooling kit.

  9. #8
    Have you checked the lashings gaps?
    if both the timing marks are lining up, check to make sure the engine is also at top dead centre


  10. #9

    2017 GP1800 fresh rebuild running rough

    To me it sounds normal my 15 fz when new was rough and would die. after 10h it smoothed out. When my tc broke and I got a new motor, new motor was rough then again smoothed out

  11. #10
    Took the cams out and started from scratch. Took a few times but it's correctly timed now and idles/revs smooth. No shaking or knocking. I've got one small oil leak on the tensioner I need to fix tomorrow and should be good. Thanks for the suggestions!

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