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  1. #1
    DavidH's Avatar
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    Just another GPR 2001 rebuild thread

    Hey, first thread started here.
    I have a 2001 GPR and I am going to rebuild it (again....). I have been reading up on options and have taken the exhaust and head off for diagnosis. I'll post questions and updates here, please chime in as it goes!

    History: I bought the ski in 2002 with 12 hours on it. Raced it in superstock for 4 years (Texas SuperCourse). It has 13/19 solas prop, removed chokes and added flame arrestors, jetted up (don't remember what at the time) and primer installed (accel pump deactivated). Intake grate (don't remember if it is riva or protec?) and Riva sponsons. Oh yeah, D plate and waveeaters before I even ran it the first time.

    It used to run 70+ at the end of the tank regularly. Blew the #2 piston around 2012. Rebuilt it (top only) in 2015 and it hauled ass again like always. For three whole days. Blew up #2 again and I put it on the trailer and waited for a rainy day.

    Now I have ordered a 2022, having ridden a friend's 2018 FX SVHO I just had to get something more reliable. FIngers crossed this new ski actually arrives!! In the mean time, I kicked my older race ski off the double trailer, and brought this one back home with one open slot on the trailer for the new ski. Reading up on some small mods I want to do to the new ski, I couldn't help but look at what it would take to rebuild the 2001 GPR while I'm waiting for it to hopefully show up.

    I see there are a few additional mods that were not in play 20 years ago. Double fuel feed, carb channel blocking (on the rail), back pressure drill out and install the 95 jet in the return line. I'm going to rebuild all the carbs and have the crank looked at (rebuild if needed, but I think it's pretty good). Going premix for sure.

    First question is, my old jug from the 2012 failure is pretty gouged. I assumed this time it would look the same so I was contemplating sending all three jugs for machining and plating (MT) and size up to 1300 pistons. Now that I have the head off, this time the cylinders look pretty smooth still. #2 will require a little work, but the damage is not enough to catch a fingernail on and does not penetrate the nickasil anywhere I can see (haven't pulled the jug off yet).

    1) Should I just stick with 1200 pistons? If so, should I re-ring the #1 and #3 pistons, or just keep runing them as is? Or just go through with resizing them to 1300, is there an appreciable gain to be had? I know I'd have to mill the head out and such. Cooling mods are in the works for opening up the head gasket on #3 and routing the hose overboard & capping the exhaust at the hose connection.

    2) If I can't find anything wrong with the crank, should I even worry about splitting the case and sending these for rework? I'm thinking I don't want to get into this engine again so yes, but would like some advise on: leave it or work it. I have never split/resealed a lower on these engines (yet).

    3) The head is pretty dinged up at the #2, pitted a bit and such. Can it be reworked (welded and milled back to shape)? I see this as an option on GroupK but wanted to know if there is more input. Haven't seen anything but used ones on ebay so far.

    I want to stay on pump gas, but I don't mind running 91 octane if needed. Would prefer to keep it on the rich side and reliable, pulling high 60's would be just fine so not really looking to bump compression up much if any.

    More to come, TIA for the comments. I have pictures soon-


  2. #2
    DavidH's Avatar
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    Click image for larger version. 

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  3. #3
    jeffg426690's Avatar
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    Pics of head?
    Splitting the cases isn't a big deal, just a bit more time consuming in your rebuild but worth doing imo. Primarily to inspect and CLEAN. Clean the crank and bearings thoroughly. You had debris flying around inside the motor, gravity says some of that debris will go down into the crank journals. There's also a strong chance with your crank seal being as old as it is, it's leaking. You can do a quick leak test before pulling it apart if you wanted to just to see what's what. If you don't open it up and clean it, you're taking a coin toss gamble of failure sooner than later. Just my 2c.
    The Oside Bill jet recipe is very reliable.
    Don't have exp with going up to 1300, not sure I would want any more stress on the crank.
    More pics & good luck with the build!

  4. #4
    DavidH's Avatar
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    As requested. Looks like 1 has some minor damage as well. Definitely made my decision to have the crank rebuilt.

    Here's the head
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  5. #5

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    We also have a 01 1200R. We have dual fed the carbs, extended and clunked the pickups, drilled return mod, Oside Bill recipe with chokes intact, run 40:1 Interceptor premix, holeshot kit, Waveater clips with PV couplers, intake grate with ground ride plate, windscreen and storage bucket mod and removed the oil tank. We’re at 69.1 on GPS with a stock prop and 155lb rider on half tank.

    We plan on doing a 1300 conversion with a milled head. Would like to be mid 70’s on a single pipe.

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  7. #6
    DavidH's Avatar
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    Got the carbs off. Woo hoo, making progress.Click image for larger version. 

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  8. #7

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    Looks like that machine has had some work done to it…. Flame arrestors, a primer kit and t handles installed

    You can call Newmiller machine about your jugs and head, chris will take the time to answer all your questions.

  9. #8
    DavidH's Avatar
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    Yeah, I did all that 19 years ago. It was bone stock when I got it.

  10. #9

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    The GPR is such a fun ski.... we hope to bore the cylinders to 1300 this winter as well. Likely shaving the head too.

  11. #10
    DavidH's Avatar
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    Click image for larger version. 

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    Shade tree mechanic FTW.

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