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idle screw

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I have a 1979 rm250n and I cannot seem to find an idle adjustment. At this moment when you let go of the throttle it shuts off...and I cannot for the life of me find the idle srew on the carb !!!!??? What am I missing???

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Sounds like you're missing an idle screw :lol: Check the parts finch for location.

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I think this is a carburetor model that uses the choke plunger as the idle adjustment (screw it in or out).  I believe this is common to some Mikuni TM and  Kehin PJ carbs.  But this is just a guess with no pictures.

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As stupid as it sounds, I think some carbs were designed not to idle.

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knudsen has it right.....it's a race bike, it wasn't intended to idle and the carb has no idle jet or idle circuit. 

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I think you can get a carb thats the same model but has an x on the end or something, swap your jets and stuff and have idle.

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Hmmm might be a later RM, I'll try to remember to check when I get home.

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Sorry, I can't find it. Just ran across it the other day looking for something else. I'm pretty sure it was an RM that came with a TM, and they said swap in a TMX. I'm not positive on the jetting, but I think it would be the same as what you have. You might need to order new jets of the same size. Dain Bramage.

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DOH! Double post

Edited by knudsen

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Any yz250 carb of the same era would be near identical but with an idle screw. I hope Suzuki was giving discounts to the original purchasers for the idle delete option. :facepalm:  

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Yup no idle.

I remember that on all my rms 78-85, but I also remember it never being a problem and not giving it a second thought. Would probably irritate me now tho. Lol

Edited by HappyG

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I think this is a carburetor model that uses the choke plunger as the idle adjustment (screw it in or out). I believe this is common to some Mikuni TM and Kehin PJ carbs. But this is just a guess with no pictures.

My '76 IT 400 idle is adjusted this way.

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Any yz250 carb of the same era would be near identical but with an idle screw. I hope Suzuki was giving discounts to the original purchasers for the idle delete option. :facepalm:  

Yah, but they pick it up on head gaskets from improper warm up :lol:

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emso, I ran across the info again. Now this is from an old book, so I don't know if you can still get the recommended carb. Also the article was on 80's RM's. The information may or may not apply back to earlier bikes.  It said to get a TMS carb from White Bros. So if that is available, they should say what it fits. If not, I think a TMX and fig out the jetting is your best bet. They went to a TMX in 89. Check your dimensions carefully. It would suck to end up with a new carb and no available boot. I am running a slightly smaller carb with a fresh pliable boot and it seals, but I'l bet it leaks sooner than it did with the stock carb when the boot dries out.

Edited by knudsen

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The Mikuni TM flat-slide on my '82 RM has no idle screw.  I adjusted the cable a bit way back when, and it's idled like a Bentley ever since. :)  The idle speed changes some when you move the bars full L or R, but otherwise I've never had problems with the carb's idle.

 

Ray

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I was thinking of that, Ray, but without doing it myself, I was afraid it would be bad advice. Might be nice if you could do that and make the end at the throttle adjustable without tools, like the brake and clutch, with thumb screws. But if it idles like your Bentley... Do you make your butler ride the bike for you? :lol:

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I have a 1979 rm250n and I cannot seem to find an idle adjustment. At this moment when you let go of the throttle it shuts off...and I cannot for the life of me find the idle srew on the carb !!!!??? What am I missing???

'79 RM250 didn't have an idle adjustment, though (get this) the RM125 did. Why they would use it on one but not the other is one of dirt bikedom's ongoing mysteries, but that's the way it was then.

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I was thinking of that, Ray, but without doing it myself, I was afraid it would be bad advice.

 

My thoughts exactly, after reading so many times how important throttle-cable slack is yada yada.  The first few times I started it after the adjustment I was waiting for it to redline or do something nasty, 20 years later I'm still waiting. :) The RM actually idles better than any of my other bikes, despite being way too rich below 1/2 throttle (I'm working on it).

 

I'm only slumming in the Bentley while the Aston's in the shop.  Hopefully the McLaren will arrive soon, I'm so bored... :D

 

Ray

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