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  1. #1

    Is my Ski down on Power/RPM? Need Advice.

    After many, many hours of reading old posts on here, my head hurts and I just need some advice!

    A quick little background:

    I bought my ski with a fresh engine that was done by a local shop for the previous owner. It ran 73 1/2 on GPS but I can not remember what the top RPM was for the life of me but could swear it was in the 7100-7200 range. After just a few hours it tore up the rear seals and it took a few more hours for me to figure out what was causing the run ability issues. Come to find out one of the seals was put it backwards.

    I pulled the engine and replaced the seals and while I was in there I took out what looked to be about 2-3 degree keyway and I put in a 5 degree keyway I bought from WFO. I also milled the head .030 more than it already was and got the squish to .052.

    Put it back together and it runs great, all previous run ability issues are gone. The thing is, the highest rpm I have gotten it too is about 6870 (via tiny tach) and I could have sworn it was over 7k prior. I didn't have the ability to GPS it but the speedo only read in the mid 60's and it was pretty accurate when I check it via GPS when I first got it. I played around with efi settings some but nothing I did made much difference.

    So am I down on power? Is this normal due to the additional timing? Does it need a different prop?

    Also I noticed if I am cruising at a little over half throttle, then jump on it, it has a brief hesitation before it takes off. Which adjustment on the controller needs adjusting to take care of this? The crossover?

    Thanks for any advice you guys can offer!

    2003 GP1300r 40:1 Premix

    EFI Settings : 5616

    Stock Milled Head .052 Squish

    5 degree timing key way.

    RIVA Girdled Head Hardware Kit
    RIVA GP1300R Power Filter Flame Arrestor
    RIVA Pro-Series E.F.I. Control Unit
    RIVA GP1300R Cat Removal D-plate
    RIVA / Boyesen Reed Stuffer Kit (66V/60T)
    RIVA GPR Free Flow Exhaust Kit
    RIVA GP1200R/1300R Top-Loader Intake Grate
    RIVA GPR Pump Seal Kit
    RIVA / Solas Concord Set-Back Impeller 13/20
    GPR Pump Exit Nozzle (87mm)
    RIVA GPR Performance Ride Plate
    RIVA GPR Performance Trim Tabs
    RIVA GPR Pro-Series Adjustable Sponsons

  2. #2
    Matt Hill's Avatar
    Join Date
    Jan 2011
    South Jersey
    What kind of fuel are you running on?

  3. #3
    93 octane. 40:1 premix

  4. #4

  5. #5
    Matt Hill's Avatar
    Join Date
    Jan 2011
    South Jersey
    Well, not to be a prick, but I think you need to do a little more diagnostic work. Can you borrow the GPS to get a new speed run? Can you check the compression on the cylinders?

    My concern with the five degree advance is that one poor tank of fuel and you may have a bit of an issue with spark knock under load. You typically shouldn't see this on the very top of the RPM range, as you shouldn't have quite as much load there. Just something to watch out for...

  6. #6
    I haven't dug into any diagnostic because I don't even know if anything is wrong with it to diagnose and that is why I am here. Like I said, it runs great. I just wanted to know, with what is done to it (mods, timing, and prop wise) should it be seeing higher than 6900 rpms and if so, how many rpms should it be turning?

    The compression was fine when I checked it, prior to replacing the seals. I have only run about 16 gallons of fuel through it since the seal replacement. After milling the head an additional .030 it should be higher now of course but I haven't checked it.

    I don't get that much time to work on the ski as I live 500 miles away from it and its just a long weekend here and there that I get to ride/work on it. I plan to GPS it when I go down and ride it again in June, but just want to be as prepared to do what I need to do to it as possible (if anything), as my time at the lake is limited.

  7. #7
    After doing some more reading I remembered something and not sure if it has anything to do with it or not.

    When I was putting the engine back in and hooking up fuel lines etc. One of the dryer hose looking tubes was getting in my way so I took it out because I noticed it was open on the end while the other one had a plastic ball on the end. I figured the plastic ball was just missing and it was serving no purpose or it was part of the factory air intake that I no longer needed.

    My ski has the Riva filter that just hooks to the intake. So should that hose I took out be feeding fresh air towards the filter? Could that be causing my low top end rpm?

  8. #8
    Nobody knows if my ski with my prop/mods should be hitting a higher rpm???

  9. #9
    Cliferton's Avatar
    Join Date
    Sep 2011
    Jackson TN
    I would say yes. I am achually batteling the same issue with my 03 gpr. as far as what I am told the ski shoild be running 7100-7200 rpm. I am beginning to think that my prop pitch is a little high. power valves appeared to be set correctly ( with servo closed the disck hole and the pv hole line up to a 4mm pin). I got rid of the ff tube and i went with ngk bre9 (side gapped and gapped to .035) that took me from 69.2 mph @ 6900 rpm to 70.7mph @ 7050 rpm. I am going to recheck my compression tommorow. I had good comp before I had the head redone 130ish on all 3. these things are goofey sometimes I am learning. here are my mods so you can compare... lol maybe we have the same issue and someone will hit the lightbulb. I know i have been buging a couple of the gurus on here and they are scratching their heads and giving test suggestions and seem to think I should be a good bit faster. here is my mod list so you can check my results against yours
    03 efi gpr
    r&d plate (trued and shimmed)
    pump shoe sealed
    1200 grate with trimmed wings
    stepped stock sponsons
    stock trim tabs resin filled on both sides and shimmed down 1mm
    ho pump with ceramic bearings
    85 mm nozel (tube removed and plugged and pisser hole plugged)
    dynafly 14/20 pitched to 14/21
    jetworks holeshot kit
    d plate and chip
    airbox gutted (tube ran from box to right side vent hose with vent cutout )
    seat air flow mod
    stock head cut to 150 psi running all 3 gqaskets (as per jim's performance)
    bre9 plugs (side gapped and gapped to .035)
    vf3 reeds with stock stuffers ground to fit correctly
    5 degree timing keyway
    ejk fuel tuner
    93 ocrane and oiler but add 1 oz of oil per gallon

    I think thats all of it maybe you saw something in there that will help you or maybe smeone will magically chime in with an answer to help both of us but I think we both are going to have to spend some time with our toys to get it right. ill keep you posted on my progress though

  10. #10
    Yea yours is very close to mine but mod and rpm wise. Well when you were only getting 6900 out of it that is. I only get to mess with mine every so often since it is 500 miles away but mid June I'll be back down there and am getting a game plan together of things to try. I am hoping that it may be starved for air since I pulled that tube out that was directing air towards the intake and didn't put it back in. So first thing I am going to put that back in. I'll gap and index the plugs. (Right now they are just the standard NGK bre9 thrown in out of the box.) Do you think the extra rpm came from the plugs or eliminating the ff? I have read a lot lately about the ff slowing you down so whats the benefit from it then?

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