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Thread: gp1200 troubles

  1. #1

    gp1200 troubles

    Hi and great site,
    I need a little help with the gp1200 motor, i have a 2001 xr1800 jetboat with 2 gp1200 motors in it they call it the xrt1200y. This boat hasn't run in about 4-5 years, I cleaned out the gas put new in and one motor started right up and ran rough, I gave it a compression test and it was way low in the last cyl so up for a bit of money there.
    The 2nd motor has good compression on all 3 cylinders, good spark, fuel to the carbs but will not even fire the slightest. It even sounds weird and different to the other motor when turning over... sounds like its being turned over to fast!? or like when you don't have the plugs in, but it has good compression 130-140 each cylinder.

    Anyone had this problem or any guesses... hope no one minds me posting this here but cant seem to find a jet boat site that is any good.

    Rod


  2. #2

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    welcome to the site, could be the carbs are plugged with crap from sitting, try putting a small amount of premixed gas in each cylinder thru the spark plug hole & see if it try's to start, if so you know it is a fuel problem

  3. #3
    mudslanger's Avatar
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    If it has been that long since the motors have been run i would premix the fuel and go with new plugs. you need to check the oil injection lines if you can bend them in a 2 inch loop without them breaking they may be ok if they are hard and brittle replace them. you may want to pull the oil supply line off at the oil pump to make sure your getting clean new oil there should be a line coming off the oil pump to bleed the air out of the oil pump. the carbs. probably need to be removed and cleaned also. compression sounds good. these motors are hard to crank sometimes you can install a primer but you can pump the throttle a few times and hold wide open wile starting that works pretty good most of the time. if you do get it to crank and its not running on all cylinders dont run it long you could fry a cylinder.

  4. #4
    Hey thanks for that, i will give it a try on the weekend and post what happens...

  5. #5
    ...
    Last edited by Pale Rider; 03-08-2011 at 07:13 PM. Reason: ...

  6. #6
    ok, i got the engine to fire, I changed the plugs, cleaned the carbs as good as i could without taking them off put a bit of premix down each cyl, turned the key and she went ding ding...ding, now before i run it to see how it runs, how do you check to see if the oil injection is working? the oil lines all seem in good condition but just not sure on how it works.

  7. #7
    also think I found out why the other engine has low compression in that one cyl, I took the air intake off and there sat the 3 carbs.. 1 & 2 both have a small pool of oil laying beside the choke butterfly but none sitting on the bad cylinder's carb.
    So i'm guessing the oil injection to that carb clogged or stopped for some reason, is that common??

  8. #8
    Yamaha artisan Cutlass's Avatar
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    Quote Originally Posted by rbjb99 View Post
    also think I found out why the other engine has low compression in that one cyl, I took the air intake off and there sat the 3 carbs.. 1 & 2 both have a small pool of oil laying beside the choke butterfly but none sitting on the bad cylinder's carb.
    So i'm guessing the oil injection to that carb clogged or stopped for some reason, is that common??
    That happened to mine. Saw a puddle of oil in the intake on 2 cylinders and one was dry.

  9. #9
    mudslanger's Avatar
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    The oil injection pumps on those engines are usually not what fails. its the oil lines going to the carbs. that shrink and pull off. as for the oil on the choke butterfly thats normal for one that has sit for a wile. if the engine with the bad cylinder still has the oil lines still attached to the oil pump and carbs. the engine may have dropped a power valve you need to remove the head and cylinder anyway to fix the problem and find the cause of the problem. if theres a lot of trash and shavings in the cases you probably need to do a total tear down to clean and check everything.

  10. #10
    Was going through the oil lines and thought I would just check the check valve on the oil line to the bad cyl and sure enough the arrow is pointing backwards. Thant might explain why its not getting oil

    Is there a way i can get that pump to pump oil up the lines without running the engine? or just pour a bit of oil down the cylinders and crank it over for a bit.

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