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Thread: GP1300R rebuild

  1. #1

    Join Date
    Oct 2019

    GP1300R rebuild

    Hey guys im new to the forum and jet skis in general. This summer I purchased my first ski, a 2007 GP1300R. After putting about 15 hours on it I was looking for a better whole shot so I installed a D-plate myself. It took me a couple of hours, but i finally got it. I was really happy with the responsiveness and speed out of the hole as well as some added top speed. I also got new spark plugs for it. Since I bought it at 96 hours, I have put about 40 hours on it. After researching some more and finding out the life span of the GP1300R is I panicked a little. The last thing I want is for one of my cylinders to go out while im riding. I looked into some builds but couldn't really find many threads on built gp1300r motors. Ive had my eye on a few top end rebuild kits and now that it is fall I have plenty of time till the next riding season. Id love to rebuild it myself im just not sure where to start. I wanted to get some more information if any of you guys know about building these. My main goal is to get a couple more summers out of it while adding some more power. How would I go about achieving this?

  2. #2

    Join Date
    Oct 2019
    sorry wrong forum meant to post in 2 strokes

  3. #3

    Join Date
    Sep 2010
    Lake Travis, TX
    Hey Kyle,

    There are four main methods of increasing power with 2-stroke engines: 1) Increase displacement; 2) Porting; 3) Triple pipes; 4) Increase efficiency. The first three methods increase the airflow through the engine while the last extracts more energy from the combustion process . As you increase power, you can force more water through the pump by using a more aggressive impeller (higher pitch numbers). Bear in mind that making these changes often requires other changes in the engine in a systematic way to maintain reliability and to achieve the expected results. For example, porting a stock engine without also removing inlet restrictions from the stock air box may yield disappointing results. Without improving the fuel delivery, the engine may be lean and become more prone to detonation/preignition and could result in a seizure from a melted piston.

    You are right to be thinking about a top end job for your engine. You need to determine what your budget is for modifications beyond the actual cost of a basic rebuild. Your cylinders may need replating and this can run $200-300 per cylinder. If your cylinders are in good condition, then you will need a Aluminum Oxide hone to deglaze your cylinders. Pistons rings and bearings will add another $100-200 per cylinder. A top end gasket set is in the neighborhood of $200. After the basic rebuild costs are covered, then you can take a look at your budget for mods and upgrades. Bear in mind that there are fewer options available today than there were 10-15 years ago when these skis were in their heyday. Nobody makes triple pipes anymore, I'm not sure anyone is making ignitions for your model anymore (although you may be able to adapt one from a 1200), R&D has closed its doors, and the list goes on. For sure you will want to pressure test your engine after the rebuild. I'm not sure anyone makes a kit for your engine anymore, so you will likely have to make one yourself.

    Having said that, there are still options for increased performance. You can port the engine, mill the head, add a fuel controller, improve cooling, remove the stock airbox and add flame arrestors, add a 3-4 degree advance key, seal the pump, change the impeller, change the intake grate, machine the ride plate.... It's all a matter of how much time and money you want to spend. Rich at WFO is a great resource and you may just want to consider crating up your engine and sending it to him for your rebuild and any mods you want to make.

    Good luck with your rebuild. I hope I haven't discouraged you too much, but you need to go into this with your eyes (and your wallet) wide open.


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