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Thread: RPM problems??

  1. #1
    "Second place is really just the first loser." YSAVE's Avatar
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    RPM problems??

    Hi guys, Iím having a problem with my 2000 Gp1200r. I bought the ski originally with a seized engine. The engine was just completely rebuilt, both top and bottom end. I finished putting the motor back in the ski, and it fired off once the carbs got the fuel. It ran great at idle for about 5 seconds, then the engineís RPMís started to increase to 5000rpm without touching the throttle! I then adjusted the throttle cable and then the rpmís still jump up to 5000+ almost immediatly. Then I adjusted it cable again (itís almost backed off as far as it will go) and the ski jumped to WOT, I pulled the tether cord and the ski didnít shut off!! Then I took off the vise grips that were connecting the battery cables to the battery and that did nothing.. Then I shut the fuel selector off and ripped the spark plug wires off to stop the engine. The ski ran for about 5-6 sec at WOT before it shut off. I then took out the spark plugs out and they look fine except the middle cyl looks lean.
    Does anyone know what I might be doing wrong? The ski sounds strong, no skips or weird noises, but the throttle is messed up. I donít know why the RPMís would automatically climb without even touching the throttle, or why the ski wouldnít shut off when I pulled the tether.. Ski only has 29 hours on it, and I just rebuilt the carbs too.. HELP!!

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  2. #2
    Moderator OsideBill's Avatar
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    Carbs are not filled yet and it is running away on you, pull the throttle wide open or choke it when this happens and it will stop.

  3. #3
    Ramps's Avatar
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    Quote Originally Posted by OsideBill View Post
    Carbs are not filled yet and it is running away on you, pull the throttle wide open or choke it when this happens and it will stop.
    I would also double check carbs just to be sure..Same thing happened to me on my 01' GPR. It was a carb issue..Oside is probably right though..Do what he recommends first...
    Last edited by Ramps; 10-03-2008 at 10:57 PM. Reason: Changed mind

  4. #4
    "Second place is really just the first loser." YSAVE's Avatar
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    Thanks Oside, I'll give that a try soon.

  5. #5
    "Second place is really just the first loser." YSAVE's Avatar
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    hi guys, I tried what Oside said, but still no luck.. The ski will only run on full choke at 3000 RPM.. When I release the choke the RPM's go up to 5-6000 RPM.. then slowly settle back down to 4000 RPM.. But then when I give the ski a little throttle, the RPM's jump to 6000+ RPM (and it stays there) then I need to choke it to bring back down the RPM's

    It's a constant game I have to play with the choke and throttle, the RPM's won't stay in the same place for more than a few sec.

    Does this sound like an air leak? I sprayed some starting fluid near the carb gaskets to see if it would rev up from the air leak, but nothing happened. The ski sounds strong at WOT, so I think it's getting the fuel it needs.

    Also, what is that adjuster knob on the front of the carbs for? (The one that is about six inches long.) Thanks

  6. #6
    Moderator OsideBill's Avatar
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    The adjuster knob is your idle adjustment have you backed it down? when you stated earlier you adjusted the throttle, I assumed you meant this. Back that sucka down.

  7. #7

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    You did go through the carbs right? This is the biggest mistake that people make when rebuilding a motor. If the motor needed a rebuild, there is a good chance that the carbs were involved in its failure. I've seen gummed up carbs cause a runaway lean condition.

    If your carbs are clean, Like Oside said, your problem is either that you idle is adjusted too high, or you have a lean condition (most likely case since rpms are not constant). The motor runs away because the plugs get red hot (lean= hot), and the engine runs similar to a diesel.
    You have to get more fuel to the motor to stop it- ie. choke or open the throttle up (last thing you would think to do). I'd bet on an air leak- check your crankcase seals, intake and even Exhaust gaskets for leaks.

    Like oside told you, make sure the fuel lines, filter, and carbs are full of fuel, and aren't the source of the air. I doubt that the carbs are set up that lean, but it might be worth a shot to check the adjustments.

  8. #8
    "Second place is really just the first loser." YSAVE's Avatar
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    Well to make a long story short, I backed the idle adjustor cable all the way back, (thinking it would bottom out).. Man was I wrong.. I had to take the stinger and air box off so I could stick my hand in there to put it back on.. Backing it off seemed to help a little, but the ski has a mind of it's own

    I'm betting it's an air leak somewhere, the middle cyl does look like it's running a little lean, and I can't keep the idle speed constant for more than a few seconds.. Also, the ski will ONLY start with full choke even when the engine is warm.

    I just rebuilt the carbs too, but I never installed the t-handles Looks like I'm going to have to take out the carbs again

  9. #9

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    either you have an air leak, or a leak/restriction in your fuel lines. Run a new fuel line from the tank pickup to you carbs to rule that out first. I'll bet on the air leak though. I myself am not a fan of the t handles since my fingers are usually too big to get in there anyway. I just use a long skinny screwdriver even when I have t handles installed.

  10. #10
    "Second place is really just the first loser." YSAVE's Avatar
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    Thanks for the help guys. I'll pick up some clear fuel line to replace the stock, this way I'll be able to tell if it's getting proper fuel.

    Does anyone know how much that small fuel container under the hood is supposed to hold? The one that fits in the little rubber boot that is labeled "UP" with the arrow The fuel in mine is just below the exit hose and idk if it's supposed to be filled to the top.

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