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  1. #1

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    Question modded 951 jetting opinions

    so i bought a 99 seadoo XPL 951 and it has a sbt motor, coffman exhaust, micro-touch, and stock air box. Im going to do the carbs and was wondering how I should be jetting this thing. Ive never had to deal with carberators before i always played with fuel injection on my toys so I dont have much knowlege of carberators. I think its already been jetted as it HAD flame arrestors according to the previous owner but now has a stock air box.(previous owner bought it off the guy who modded it) Plugs are getting fouled out and is running very rich. Im going to get the flame arrestors and was wondering what jets i should use with this combo. thanks
    Last edited by formula355lt1; 08-27-2011 at 09:54 PM. Reason: add info


  2. #2
    mibunkerking's Avatar
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    Find out what you have first. Pull the carbs and check the jets for size as well as the needle and seat. Then report back. To run that pipe it had to be rejetted or it would have seized already. The question is what jets did he use. They don't call them the purple piston eater for nothing.

  3. #3

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    well what kind of jetting should it have with these mods? Im having someone else do the carbs and dont want to have them pulled apart till i know what i need. Well heres the story on the ski. The previous owner bought the ski with a bad motor from the guy who did the mods. The guy said the motor got water and locked up, the guy bought the ski and put a sbt motor in it and had a shop install it. Prevously it had the exhaust flame arrestors, and a microtouch installed. The shop told the guy the flame arrestors were bad for the motor and took them off and put on the stock airbox. I got the ski and it didnt run right it had no power and wouldnt go past 6500rpm but it had the old fuel lines so i figured that was the problem. I replaced them and put in new plugs. Now it runs like crap feeles like its missfiring and running on one cylander till its warmed up all the way then runs better but still lacks power and will go to 7500rpm for a few secounds then will fall to 6500. After about 30min on the water it looses power and wont go past 6k and feels like its powerd by a lawnmower engine. Pulled the plugs one is rich and the other is really rich. Looks like the guy Ported the carb a little too but not that great of a job if you ask me. I figure its the carbs but im clueless about carbs and tuning them so Im having it done by a friend. He can rebuild them but doesnt know what jets it should be running with the mods. Maybe there just not tuned right? Does this sound like carb probllem?

  4. #4
    SURFnTURF's Avatar
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    Hi yes if your running coffman exhaust i would go with this set up

    Accelerator pumps working --- Lows 87.5s open 1.5 turns from closed , Highs 172.5 closed , 2.3 N/S pop off 19 psi
    Accelerator pumps not working ---Lows 95 open 1.5 turns from closed , Highs 172.5 closed ,2.3 N/S pop off 19psi

    This is a safe jetting config,I actually use 95 lows and 170 highs closed with no pumps. You have to use a good quality digital tacho (fast refresh rate tacho like .5 sec) and when you open the throttle it should instantly get to 7250-7300 dependent on prop pitch and stay there.If it drops off even 20-30 revs it is too lean and either open high speed screws or jet up one size.
    If it has trouble getting over the 7000 rpm hump as some can do your prop is to tall and will need re pitching. I re pitch the stock prop which is 14/21 to 13/19 which relieves some stress on the engine.These have to be revving into the 7300s to make good power and lessen engine stress due to to tall a prop.Make sure the wear ring in the pump is good as this will affect performance because it will be processing allot more water through it now.Use the stock intake grate as well. Hope this helps.

  5. #5

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    ok the carbs have 170 high jets with aftermarket ajusters for the highs, how many turns from closed should i do for the high jets? one carb was all the way closed and the other was open 1 turn. Dont know what to set them at any one know what i should have them at?

  6. #6
    SURFnTURF's Avatar
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    Quote Originally Posted by formula355lt1 View Post
    ok the carbs have 170 high jets with aftermarket ajusters for the highs, how many turns from closed should i do for the high jets? one carb was all the way closed and the other was open 1 turn. Dont know what to set them at any one know what i should have them at?
    If you are going with 170 highs and want a little more fuel, opening the adjusters 1 full turn will give you approx 5-7 more base points. The low speed jets play a part in the overall jetting as well so they need to be as above depending on if accelerator pumps are used.

    For starters if a little unsure of tuning open them both 1 full turn and then its a matter of riding and tuning.

    It will be rich so don't expect revs to be up near 7300 .

    You need a good refresh rate tacho as well.

  7. #7

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    thanks surfnturf, im waiting for the shop to call me i orderd prok flame arrestors and need them to tune it on the water.(hoping for today) I should start with the high adjusters set at 1 turn from closed and go from there?(i was gonna go 1.5 on both) I read somewhere that you want the pto side about 1/4 turn more open than the mag any truth to this? I am using the accelerator pumps. I believe my low jets were 85's. So does 1.5 Highs and 1.5 lows sound good for a baseline adjustment? Also not sure what you mean about base points... What kind of rpm and speed can i expect from this ski with stated mods and stock prop? thanks.

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