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Thread: 1981 rm 125

  1. #1
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    1981 rm 125 carb problems

    i have a 81 rm 125 i just picked up for my son.the engine is rebuilt top to bottom.its bored .80 over the problem im having is when i start it and get the motor warm the engine runs great with the choke on it runs smooth and burns clean but dies when i twist the throttle.when the choke is off it pops blows smoke and runs like crap.i have cleaned the carb and adjusted the mix.it doesn't make a difference?Im stumped





    ANYBODY HAVE ENY SUGGESTIONS ? (THANKS)
    Last edited by clarkbd; 04-30-2009 at 03:10 PM.




  2. #2
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    Rebuild your carb. You might start by rejetting your it, but your problems sound worse than jets will cure. I have an 82 RM 125 and run a 27.5 pilot and 250 main....but will vary from bike to bike.




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    "get the motor warm the engine runs great with the choke on it runs smooth and burns clean but dies when i twist the throttle.when the choke is off it pops blows smoke and runs like crap"

    that sounds wierd usually you should have more smoke with the choke on?!?
    any how if you are not familiar with dirt bike carbs make sure there is a clip holding the jet needle in place(could explain why it dies when you give it throttle) and the throttle slide isn't in backwards(kinda hard to imagine since they usually have some type of tang and slot orientation.)

    is it the original carb and the slide is worn out? is it a replacement carb and the jetting way out of whack? when I was comparing buying a new carb from a outlet type of place even though it would be the same style and size carb as stock I have never seen them come with jetting anything close to what came original with the bikes I have owned
    anyway I think you have some homework to do with that carburator




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    thanks' i picked up a rebuilding kit i will try to rejett it and see what happens.this is the carb that came with the bike its a 32 not sure if its original or not. anybody know what came on those bikes in 81




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    i took the carb apart and the main jet is 200 and pilot is 50. pulled the plug and its dark black. should i go with a 250 and a 30?




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    The pilot is a 50?? Are you sure? That is a huge pilot jet for a 125. Depending on the mix ratio you are using, I would try a 30 (stock jet) or smaller. You will need to experiment with the main jet and find out what works....like I said, it varies from bike to bike. Read the jetting threads on this site.




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    1981 rm 125 bad crank seals

    finally found out y the bike wont run rite no matter what i do to the carb.the crank seals r leaking 2 Suzuki mechanics told me that was the problem.the engine sat to long and the oil is leaking through the seals.anyone no where to get the seals besides the dealer.




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    I was just about to say check you Crank Seals. These are great bikes. I used to have a 1982 Suzuki RM125 with a Krause Kannon Pipe (equal to a DG pipe), Krause Kannon Silencer (equal to a DG Type II silencer), went down 2-Teeth on the Rear Sprocket for more Top-End speed and man that thing ripped. I also had the Ceet Safety Seat Kit with the Blue Seat Cover.

    I still say to this day that was the best bike that I ever owned and fastest 125cc bike that I have ever ridden.

    Great pick up for your son. I hope he enjoys it.




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    The crank seals for my 82 125 were $6 from Suzuki...its not the cost of the seals, its the labor to install. Have you measured your oil to make sure it is burning gear oil? Fill it (800 ml), then ride for a few hours, drain it completely, then measure it...that is a good test. I tore mine down thinking it had bad crank seals....it didnt.




  10. #10
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    i ran the bike for about 45 minutes and the oil was low thats what gave me the clue then i talked to the mechanics.




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