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Thread: motor wont idle down

  1. #1
    Join Date
    Nov 2013
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    bayou state
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    motor wont idle down

    I have something I cant figure out here, I have the hemi bottom end that a put an rtc8 head on and now it wants to run about 1500 rpm , the same carb ,same air filter same every thing just changed the head, I tried a different carb same thing I changed the insulator and gaskets ,same thing ,whats up

  2. #2
    Join Date
    Apr 2015
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    12
    did you try adjusting the idle adjusting screw?

  3. #3
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    yep its not even touching it and tried a different carb

  4. #4
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    Apr 2015
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    is there a throttle linkage hooked up? i know the linkage i was running on mine was binding up at idle and i had to bend the one rod that hooks to the top of the carb on the black piece

  5. #5
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    if there is no change when you monkey with the idle set screw, then you have an issue with the throttle rod holding it at a set rpm....trying grabbing the throttle rod with two pair of pliers and bending it until the engine idles down and the black plastic piece the rod slides into hits the throttle stop. one very easy way to check this is to remove the throttle rod and start the engine. you might have to get someone to help so that you can get it started, but once you have it going, make sure the throttle is hitting the stop and then try to adjust the idle. if this works, then you need to make adjustments to the rod itself.

  6. #6
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    thanks for the help but yall don't understand, all that is good even with no throttle rod hooked up it does this and I have been running that motor for a few races and all I did is change the head to an rtc8 ,its like it is pulling in air from some where but I changed gaskets about 5 times and even the insulator just to make sure and the carb

  7. #7
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    Oct 2013
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    i think our clone idles around 1600
    CHAINDRAGGONE SYSTEMS

    TRACK TAC TREATMENTS
    Roll N Prep
    bank of mom and dad
    JAMMER RACING CLUTCHS
    UNCLE FRANKS KARTING
    CENTERPOINT GRAPHICS " PAID B4C SUB"

  8. #8
    Join Date
    Apr 2015
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    also is the motor warmed up? i know my predator idles lower at more of an operating temp

  9. #9
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    Oct 2013
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    Spray carb cleaner around the intake port of the head, the carb and the insulator plate while engine is running, if rpms increase when you spray it, you are pulling air in somewhere. Could be a cracked casting from the factory, It can and does happen

  10. #10
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    Mar 2014
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    santa rosa,california
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    Quote Originally Posted by fastbraden11 View Post
    i think our clone idles around 1600
    This was my thought too-mine idles roughly around 1800

  11. #11
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    looking back at what your wrote, I read too much into it....do as W5R suggests....if you have any air leaks, this will show....idling at 1500 isn't a bad thing...I went back to my notes and that's about where I'm at. does the engine run up to racing rpm easily? does it skip or act up when your at speed or is it just when your sitting on the grid or warming the engine that it won't throttle down? does it act like it won't throttle down after it's warmed up or right away? heat will cause a crack to widen and allow more air in once the engine gets up in temp, but it acts fine when it's first started and cool.....

  12. #12
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    Oct 2013
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    Sounds like the idle mixture is lean. Why would you want it to idle at lower RPM anyway? RTC-6 head might flow more air at idle then the Hemi thus making it lean. Increase the idle jet size a little.

  13. #13
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    Oct 2013
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    Stupid question. Why would you care if the engine will idle in the pits? To me, the most important thing is getting off the turns, and having the low speed jet feeding enough fuel. I know with our two cycles, with the low speed jet set for the best performance on the track, it wouldn't idle in the pits. Of course with the WB3, you could lean the needle down on the low speed when needed. With fixed jets, you don't have that option. Still, I'm thinking the best performance on the track outweighs anything in the pits.

  14. #14
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    it idles too fast ,heck the clutch wants to come in
    Quote Originally Posted by alvin l nunley View Post
    Stupid question. Why would you care if the engine will idle in the pits? To me, the most important thing is getting off the turns, and having the low speed jet feeding enough fuel. I know with our two cycles, with the low speed jet set for the best performance on the track, it wouldn't idle in the pits. Of course with the WB3, you could lean the needle down on the low speed when needed. With fixed jets, you don't have that option. Still, I'm thinking the best performance on the track outweighs anything in the pits.

  15. #15
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    Oct 2013
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    1500 is not to fast. Some carb experts will tell you to keep them idling above 2000 to keep the plug from fouling. The clutch is probably not engaging, just rotating on friction. If you can CAREFULLY stop the tires from turning, its not engaged.

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