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  1. #1

    Join Date
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    Portland, OR area
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    '99 GP800 Engine rebuild

    Hello, I am new to the forum. Wish I would have found it sooner.

    I am rebuilding a GP800 engine that I blew last summer. It seems that either one of the power valves fell into the cylinder or the wrist pin clip came loose and destroyed the cylinder. Either way, I am now with no working ski.

    I did some research on things I should do for a rebuild and decided that I do not have the resources to do the rebuild. So I found a couple of shope/places that will do it.

    I first found SBT, but seen A LOT of bad reviews on their rebuilds. So I opted to not go with them.

    I than found PWCENGINES. They seem like it was a good choice, but they're in New York, and I am in Oregon. So I kept looking.

    I found ShortBlaocks-R-Us and seen that they are out of California and found some ok reviews of them here on Greenhulk. SO I decided to go with them.

    I spoke with the last two shops listed, and felt like SHORTBLOCK was the better choice for me since they are on the west coast and also liked that my cylinder will be replated and not sleeved.

    My question to everyone, was this the smartest choice? The choice being, 1) the shop? 2) the Rebuild? 3) Replated or sleeved?

    I am hoping that the rebuilt engine last me a long time, but am worried that it might not.

    Should I sell it and get a 4 stroke?

    I welcome all feedback,

    Thanks!


  2. #2

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    Feb 2014
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    Bump

  3. #3
    Happily Self-Employed WFO's Avatar
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    You should be able to get that one rebuilt and get more life out of the craft without going 4 stroke.

    Definitely go with the nikasil plating over sleeves.

    Problems with these budget rebuild places are the use of inferior parts. They have to keep costs down to be competitive with SBT, so usually the parts (bearings, pistons, gaskets) are cheaper quality than OEM.

    When I overhaul these engines, I try to use only OEM parts. (depending on the customer's budget). I may go to ProX pistons vs OEM, but I never skimp on seals, gaskets, or crankshaft parts.

    Also you will want to go thru your carbs and rebuild while you are there

  4. #4

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    Feb 2014
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    Portland, OR area
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    Thanks for the reply WFO.

    I would love to use OEM parts cause they usually are better quality, but like you said, The cost for these parts are pretty high. I am going with Wiseco Pistons. I hope these are good. As for the crank, I'm not sure exactly what manufacture the parts are, but I specified that I didn't want SBT or chinese made parts. The only thing I can hope, is that he is true to his word and uses quality parts.

    On rebuilding the carbs, what is required if I decide to do a oil pump "block out" kit? Do I need to rejet my carbs, or will the stock jets be ok and just rebuild them with a rebuild kit? Also, what would be the proper oil to gas ratio/mixture?

    I will post more info and pics as the rebuild/reassembly continues.

    Thanks!

  5. #5
    Happily Self-Employed WFO's Avatar
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    Sounds like you are already committed to this guy rebuilding your motor.

    Wiseco pistons are usually forged, and require different specs than the standard cast pistons.

    Oil pump block-off is fine, just be sure to keep an eye on mixing the correct ratio. I recommend 40:1

    The GP800 carbs were almost fine as far as jetting in stock form, just clean everything out and replace soft parts, and needles valves if needed.

  6. #6

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    Yea, Pretty much committed on the rebuild. Just hoping for the best!

    What do you mean by "Wiseco pistons are usually forged, and require different specs than the standard cast pistons"?

    How about the WSM Platinum Pistons? Are they pretty good?

    I'm planning on going thru the Carbs completely. I've seen that 32:1 & 50:1. I think I'll just go with your recommendation of 40:1. (average)

  7. #7

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    Here's what my engine looked like when I opened it. AWESOME, right? lol


    Click image for larger version. 

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  8. #8
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    Wisecos are good pistons but can sometimes present their own set of issues. For a rec boat, WSM pistons are fine. I have used them a bunch with good luck.

  9. #9
    To answer the above question, a forged piston will expand at a faster rate than the surrounding cylinder so you have to leave a larger clearance for the piston or a bigger bore so that it doesn't seize on initial warm up. It requires precise machining and careful operation for the life of the engine. There are lots of opinions both positive and negative on the WSM's. I just installed a set in an 800 and so far so good. If the person putting the engine together leaves factory clearance for the piston, you should be fine. Stick with OEM for the seals and gaskets, and use mikuni rebuild kits. The penalty for saving a few bucks on these could mean a new engine... Keep the bent rod as a conversation piece. It would make a gnarly paper weight.

    On the topic of plated vs sleeved, on the 800, the cost of getting an existing one replated is 250 or more per cylinder plus the cylinder. It looks like you have have to find another cylinder and get your "good one" replated. A sleeved cylinder runs a little hotter than the plated one and the industry has gone to the plated ones for a reason. Like the pistons, a recreational ski would probably be ok with the sleeves but cost wise the sleeves are close to the same as sourcing replated ones. As you are probably discovering, rebuilding an 800 aint cheap. Sad but true. Good luck and use synthetic oil. No recommendations but search the site for what other say to use.

  10. #10

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    CNYMAN, Thanks for your post and suggestions. I did go with the replating option. I found a good core cylinder to replace the damaged one. Both are replated and using Wiesco pistons. The crank was also rebuilt. Now I'm just waiting for my carb rebuild kits. Hope all goes well. Thx!

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