Rm125 wont idle.

LilZebb
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LilZebb
Edited Date/Time 7/31/2013 6:10pm
So I picked up a 2003 RM125 yesterday that's fairly fresh and runs great. But I cant get the bike to idle, and that's my only problem. I even checked the carb and made sure everything was clean. I tried adjusting the idle from the throttle and the carb, no luck. Any ideas? I didn't find an idle screw. It has a Mikuni Carb if that helps.
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KICKERMAN360 7/2/2013 2:54am
7/2/2013 2:54am Edited Date/Time 7/2/2013 2:55am
How long are you trying to make it idle for? Or how long does it idle for at the moment? A 125 at most should idle for 10 seconds or less. Some riders don't even set their bikes to idle. Basically, a 125 should be WOT or turned off. Go watch any small bore 2 stroke races and you'll see people continually blipping the throttle in an effort to prevent fouling.

Generally OEM specs are dead on. If you've set the carb as the service manual says, make sure the air boot clamps are tight and have no leaks. Also inspect the air boot for cracks (an 03 model should be fine though). Also check the compression. OEM specs have never let me down. I've set bikes I've never even heard or seen run to OEM specs and they started and ran perfectly.

I can't speak for Suzuki, but my idle screw on my 125 was like... part of the choke. But that carb is a Khein. Might be a good idea to check the service manual.
LilZebb
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LilZebb 7/2/2013 10:59am
7/2/2013 10:59am
KICKERMAN360 wrote:
How long are you trying to make it idle for? Or how long does it idle for at the moment? A 125 at most should idle...
How long are you trying to make it idle for? Or how long does it idle for at the moment? A 125 at most should idle for 10 seconds or less. Some riders don't even set their bikes to idle. Basically, a 125 should be WOT or turned off. Go watch any small bore 2 stroke races and you'll see people continually blipping the throttle in an effort to prevent fouling.

Generally OEM specs are dead on. If you've set the carb as the service manual says, make sure the air boot clamps are tight and have no leaks. Also inspect the air boot for cracks (an 03 model should be fine though). Also check the compression. OEM specs have never let me down. I've set bikes I've never even heard or seen run to OEM specs and they started and ran perfectly.

I can't speak for Suzuki, but my idle screw on my 125 was like... part of the choke. But that carb is a Khein. Might be a good idea to check the service manual.
Mine doesn't idle at all if I let off the throttle it dies. But what you're saying makes sense, I think I can live with it.
JCollins762
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JCollins762 7/2/2013 4:37pm
7/2/2013 4:37pm
Well your actual idle adjustment screw is on the left side of the carb, its a small phillips head with a 8mm lock nut on it. I believe turning it in will raise the idle.. but that will be apparent while you're adjusting it.
LilZebb
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LilZebb 7/2/2013 6:25pm
7/2/2013 6:25pm
JCollins762 wrote:
Well your actual idle adjustment screw is on the left side of the carb, its a small phillips head with a 8mm lock nut on it...
Well your actual idle adjustment screw is on the left side of the carb, its a small phillips head with a 8mm lock nut on it. I believe turning it in will raise the idle.. but that will be apparent while you're adjusting it.
mine is pushed all the way in? does that mean i need a smaller pilot?

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Zesiger 112
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Zesiger 112 7/2/2013 6:34pm
7/2/2013 6:34pm
KICKERMAN360 wrote:
How long are you trying to make it idle for? Or how long does it idle for at the moment? A 125 at most should idle...
How long are you trying to make it idle for? Or how long does it idle for at the moment? A 125 at most should idle for 10 seconds or less. Some riders don't even set their bikes to idle. Basically, a 125 should be WOT or turned off. Go watch any small bore 2 stroke races and you'll see people continually blipping the throttle in an effort to prevent fouling.

Generally OEM specs are dead on. If you've set the carb as the service manual says, make sure the air boot clamps are tight and have no leaks. Also inspect the air boot for cracks (an 03 model should be fine though). Also check the compression. OEM specs have never let me down. I've set bikes I've never even heard or seen run to OEM specs and they started and ran perfectly.

I can't speak for Suzuki, but my idle screw on my 125 was like... part of the choke. But that carb is a Khein. Might be a good idea to check the service manual.
I have a 2005 yz 125, it wont idle long before it dies. I cant even rev it and put my goggles on before it cuts off. As long as it runs good everywhere else and isn't idling high I wouldn't worry about it.
LilZebb
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LilZebb 7/9/2013 7:43pm
7/9/2013 7:43pm
would a missing/old carb o-ring or gasket cause it not to idle?
Skerby
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Skerby 7/10/2013 1:05pm
7/10/2013 1:05pm
If it's turned in all the way and doesn't idle, you are missing something.
seth505
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seth505 7/10/2013 6:20pm
7/10/2013 6:20pm
Sounds like your idle screw might be screwy but also check for air leaks, so make sure the carb side is all sealed up (boots going to carb and reed valve boot) and also make sure the exhaust side is good (pipe oring, etc).
Jakes Dad
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Jakes Dad 7/11/2013 4:02am
7/11/2013 4:02am
Ya spoused to hold dem' bitches wide open anyway, just ask my kid!!!Woohoo
project racer 7/11/2013 12:34pm
7/11/2013 12:34pm
When you have the carb off, take a look at the slide through the front or rear of the carb as you turn the idle screw. Turn it in and out. You should see a slight bit of movement as the screw is turned . In would raise the slide, out would lower it. The screw could be worn, or possibly a divot has developed in the slide.

Most air leaks would cause a lean condition, creating a high idle situation.
motoxer66 7/12/2013 5:49pm
7/12/2013 5:49pm
its a two stroke......its not supposed to idle.....hold it wide open you sonbitch hahaha
LilZebb
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LilZebb 7/13/2013 12:04am
7/13/2013 12:04am
Jakes Dad wrote:
Ya spoused to hold dem' bitches wide open anyway, just ask my kid!!!Woohoo
your kid has it glued open! It amazes me!



I can live with the bike not idleing, but I did have a very worn o-ring that let gas seep from the bowl. I don't know if that would affect it.
And another question what is a good general gearing for these bikes? My bike was supposedly set up for supercross. too much low end for what I ride.
motoxer66 7/31/2013 4:21pm
7/31/2013 4:21pm
the blown o-ring in the bottom shouldnt affect that at all unless its just pouring out..

12/49 is stock...my friend runs a 12/50..same bike.. for motocross if that helps..also hes a C/B rider
Jakes Dad
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Jakes Dad 7/31/2013 4:32pm
7/31/2013 4:32pm Edited Date/Time 7/31/2013 4:34pm
My little shit has a 13/51 on the 125 and the mod 150 motor pulls a 13/49
All thanks to TDC 2 Stroke Performance to get these motors pulling that good of gearing in the soft stuff down here!!
Both cylinders just went back for some tweaking after he found significant hp and more importantly torque to get Jake ready for the Gold Cups coming up.
Foghorn
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Foghorn 7/31/2013 6:10pm
7/31/2013 6:10pm
If it means anything at all, my CR500 idles perfectly. ;o)
Wayne_VintageMx_87_Yz125 6/21/2016 2:20am
6/21/2016 2:20am
I got a 87 Yz125 runs great real strong, but ever since I replaced kick starter spring bike wil not idle. I need it to idle at least 10 to 15 seconds the way I ride. Also if there is a problem I want to know before causing any more problems. I took off side cover replaced spring and spacer to the starter. I replaced all gaskets I had to remove during repair. Bike runs real strong attached a link to show a little ride after the repair but I have no idle now and carb was just cleaned a day or two before starter spring replacement. It doesn't idle on choke nothing idle wise bike will die without giving throttle. Also new starter repair works great goes down and pops right back in place. It's a one kick start always never a problem or any work to start 98% of the time just one kick and she fires right up and runs strong a lot stronger than most of people's newer 125s. Please help I need a idle at least 10 seconds. Any tips ideas are greatly appreciated. Here is the link to the ride after repair just to show its still real strong and runs great just can't get it idle and it's driving me nuts because it's time to ride lol. Thanks again for any help or tips! https://youtu.be/xwftLQE_WPo
fouledplugs
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fouledplugs 6/21/2016 8:25am
6/21/2016 8:25am
Just trying to come at this at a different angle...have you checked compression and see it is in the parameters of the service manual? Seen guys chase tunes on carbs and never achieve their desired result and the issue end up being an engine in need of a top end or something.

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