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  1. #1

    Seized #1 piston gp1200r- mod carbs?

    Hey guys my GP1200r shut down on me over the weekend while cruising at about 30. Thought it was going to be the worst case scenario and have carnage when I pulled the head off. i just had the cabs off 2 weeks and 7 hours on the motor ago to sand the throttle bushings down due to sticking. compression was 110 110 75 with the snap on comression gage hose being really long so i figure 5-7psi higher. well i got the head off and the piston was all in tact but the cylinder walls have some build up on them from the rings, can probably be cleaned with some muratic acid. looks like it was not getting any oil in that cyl. but it must have come off at the pump. so im probably going to do all the pistons while its apart. my question is should i have the carbs sent out to modify with new jets and t handles and put the flame arrestors on while i have it apart again? how much would something like that cost? what is the top of the piston supposed to look like in ideal conditions? the two cyl's that were fine have some bare piston showing and the rest black but the low compression one is all black, is it running to lean or is that how stock is? or should i just rebuild and keep stock? what gaskets should i be replacing? also the small black o ring rubber bushing that are on each side of the throttle shafts does anyone know where i can get a few of those? ADD: ski idled great with crisp throttle response at all rpms, but last week for the first time it did this i was taking some kids for a ride and after coming to a slowdown and idling for a few minutes then trying to reacclerate it stalled on me. is this a lean condition? only did it twice in the 7 hours since i had the carbs off

    Thanks in advance, Josh


  2. #2
    TX21's Avatar
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    Look up the t-handle write up OSIDEBILL did. I did mine at it works great. You will have to look up all the parts on boats.net. Cost a bit but its worth the money to know your motor will run almost forever. F/A filters cost more than the t-handles and other stuff I think. Pull the oil pump and pre-mix. Add Stabil Marine grade every time you fill up and it will never let you down.

  3. #3
    Ok got all of the cylinders off off and the one that siezed will have to be replaced or replated. The oil line came off at the pump. When replated is it back to stock bore? But the rear cylinder has some markings on it and the piston is scarred up but the compression was good hopefully i can just clean it up. I ordered updated lines on ebay that come with metal pinch clamps but seeing the condition of cyl 3 ill probably go pre mix. Ill post pictures tomorrow if i can... last question when looking for the number on the cylinder to order the right piston is it the number on the side facing the rear? In my case y- 4
    Last edited by jdmak13; 07-02-2014 at 09:57 PM.

  4. #4
    TX21's Avatar
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    They can re-plate them back to stock if the dammage is not too bad. Cost $250-$300 per hole. The numbers are stamped on the top. Here is my auction on ebay. This one is stamped #14 see the top right corner. http://www.ebay.com/itm/261522858316...84.m1555.l2648

  5. #5
    I sent my cylinder off to Millennium Technologies (MT) to be fixed and recoated. Every one I talk to says they are the best. I haven't received the cylinder back yet so I cant speak yet of the job they did. It is costing me $260 with shipping. Your price could vary some. MT told me that they are fixing it back to stock specs and I should go with the A piston size.

    Only bad thing is turn around time from MT. Since I am on the West Coast it is about a week to get it to MT and a week to get it back. Then maybe a week or so for them to do the work.

  6. #6

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    I would update the carbs to the F/A's, jets, and accell pump removal. That single mod works wonders for performance and gets ride of a potential issue of running to lean in the midrange. Don't count on all the damage being from the oil line, you will want to pressure check the engine to make sure you do not have any air leaks which will cause leanness and damage to pistons/walls.

  7. #7
    TX21's Avatar
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    Quote Originally Posted by canon714 View Post
    I sent my cylinder off to Millennium Technologies (MT) to be fixed and recoated. Every one I talk to says they are the best. I haven't received the cylinder back yet so I cant speak yet of the job they did. It is costing me $260 with shipping. Your price could vary some. MT told me that they are fixing it back to stock specs and I should go with the A piston size.

    Only bad thing is turn around time from MT. Since I am on the West Coast it is about a week to get it to MT and a week to get it back. Then maybe a week or so for them to do the work.
    That's who did the ones I have for sale. Look in the classifieds I have three done ready to go from millennium no core needed

  8. #8
    How do you pressure test the engine to make sure you don't have an air leak? Also would an air leak cause damage to multiple cylinders and not just one?

    Quote Originally Posted by LT1GMC View Post
    I would update the carbs to the F/A's, jets, and accell pump removal. That single mod works wonders for performance and gets ride of a potential issue of running to lean in the midrange. Don't count on all the damage being from the oil line, you will want to pressure check the engine to make sure you do not have any air leaks which will cause leanness and damage to pistons/walls.

  9. #9
    TX21's Avatar
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    Quote Originally Posted by canon714 View Post
    How do you pressure test the engine to make sure you don't have an air leak? Also would an air leak cause damage to multiple cylinders and not just one?

    Quote Originally Posted by LT1GMC View Post
    I would update the carbs to the F/A's, jets, and accell pump removal. That single mod works wonders for performance and gets ride of a potential issue of running to lean in the midrange. Don't count on all the damage being from the oil line, you will want to pressure check the engine to make sure you do not have any air leaks which will cause leanness and damage to pistons/walls.
    Would likely cause it to one cylinder first. Depends on where the air leak is. There is a tool kit you can buy to block off all the ports on the motor so you can pressure test it.

    I think it was $150 ( or so) I can't remember where I got it but it was someone from here that makes them.

  10. #10
    I couldn't find your listing in the classified

    Quote Originally Posted by TX21 View Post
    Quote Originally Posted by canon714 View Post
    I sent my cylinder off to Millennium Technologies (MT) to be fixed and recoated. Every one I talk to says they are the best. I haven't received the cylinder back yet so I cant speak yet of the job they did. It is costing me $260 with shipping. Your price could vary some. MT told me that they are fixing it back to stock specs and I should go with the A piston size.

    Only bad thing is turn around time from MT. Since I am on the West Coast it is about a week to get it to MT and a week to get it back. Then maybe a week or so for them to do the work.
    That's who did the ones I have for sale. Look in the classifieds I have three done ready to go from millennium no core needed

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