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  1. #1

    Best Bang for the buck

    Hey everyone, I'm new to the watercraft sport but I've got a lot of experience with 2 stroke and 4 stroke engines, I have my own machine shop and I am capable of a fair amount of mods to engines. I've been racing ATVs for while and this is a new sport I sort of fell into, so i'm learning what I can about it.

    I just recently acquired a '99 900 STX with 131 hours on it, and it seems to be in good shape. I took it out last weekend for the first time and it ran pretty strong, a little rich from what I could tell, but strong.

    The only thing I did was install a pump primer to eliminate the long times to get it started when it was cold at the dock. I noticed when I slammed on the throtle from idle, it boggs sometimes then picks up and goes fine. When I am at full throttle and I drop the gas and let it run back down to an idle, it stalls. Is that normal or is that a side effect of the fuel primer I installed?

    My next question is what is available for mods on these? I know you can get an impeller, but is there aything else? Keep in mind I don't know aything about how a PWC moves other than it pulls water in from underneeth and pushes it out the back. Is there a prop and impeller? When you change one should you change both if there is? It maxes out about 44MPH on an average day on the lake (not glass.)

    It probably needs some reeds, maybe rings, but it runs good enought for right now I'm not going to tear the motor apart. Are there other thing that need to be maintained; things that need to be replaced ever so often? Bearings? shafts?

    Thanks in advance, I appreciate the help

  2. #2
    Are you basing your 44mph off the speedometer on the ski? Usually they show faster than you're actually going, and even so, most of those skis top out at around 50ish in reality, give or take some.

    Have you checked the compression in it? It's not normal for them to die, so it may be a little problem.

    When you say it bogs after idle, that could be a problem, or it could be the water pushing out and sometimes that happens (usually after having it off). The water settles inside and then is thrushed out quickly, causing it to bog a bit on take off.

    But I don't know too much.

  3. #3
    Yes, I base the speed off of the speedometer on the dash, it's more of a refrence than anything, the guy I got it from said that's what he always saw as a top speed, about 44-45 MPH.

    Yes I am also talking about it bogging after sitting at idle for a little bit of time, so it sounds like it's pushing the water out after being stagnant, and it's jjust straining the motor momentarily. If I let it idle for a few seconds it's not as bad, but if I sit there for a longer peroid and slam the gas on, it boggs a little then zips right back to life. If I slowly hit the gas, it does fine.

    I was thinking that when I am at full throttle and drop the gas it probably stalls because it has a lot of fuel in there and chokes it slightly. If I slow down gradually it's fine.

    What is the idle RPM suppose to be at?

  4. #4
    If no one can or wants to answer my questions, then where can I find my answers?

    I want to know what kind of bolt on mods the 900STX could use and what kind of gain I can expect. WHat's the best bang for the buck as far as mods? I'd like a little more takeoff and overall speed; is that even possible?

    Any help is appreciated

  5. #5
    pokechop2006's Avatar
    Join Date
    Jun 2009
    summerville sc
    wel on your idle ive got an ultra an its set at 1200 rpms in the water,i figure thats a base line for most kawi 2 strokes.on your bog could be a few things first look at your plugs,are they burning, black also could be a sign of running too rich,change em an see how it runs,also remember that the longer you idle around the easer the plugs foul so it might take a second or two to burn you warm up the ski when you first ride?

  6. #6
    The plugs look a little rich, but I was also a few thousand feet up in elevation, and I'd rather run a little rich than lean. The plugs have about 10 hours on them or so.

    I always try to warm the bike up for a good amount of time because I know you can seize the engine if you don't...LOL! A friend of mine started his Banshee, got on it and went screaming off and about 30 seconds later he seized both cylinders. Several hundrand dollars later...

    I'll turn the RPMs up then, I thought 800 sounded a little low; but there again that could have lowered slightly because of the elevation.

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