Ok, so picked up a 1994 rm250 for 500 bucks a couple weeks ago. I rebuilt the top end, carb, and put new reeds in it (boysen super stock). The crank seals were replaced also and ive tripple checked for air leaks. Ive also set the float height to the correct level and double checked it. The air filter and vent lines on the carb are also brand new. Stator and coil both tested good. Im just shy of 5500 feet above sea level. The stock jetting is 180 main (im running a 170) 52 pilot (im running a 50) and needle clip in the 3rd position (I have it in the 2nd). The carb is still the stock one so its a Keihin PJ38. I am a little stumped on why this thing wont idle, it wont idle no matter what I do with the idle adjustment on the choke or the air screw. Anybody got any Ideas?
Can you make it idle if you hold the throttle partially open? Or does it just die under 1/8 throttle?
@minton33 it’ll stay running if I hold the throttle just a little bit open yes. And you have to have the throttle open to start it, and that’s why I suspected float height.
Have you tried turning in the idle screw until something happens? Its possible for whatever reason its just turned out way too far. If the bike will hold a normal idle with the throttle slightly open it sounds like its just idled too low. All the idle screw does is just hold the throttle slightly open. Turning it in will eventually have an effect.
Get it started and keep it idling with the throttle and then just turn the idle screw in until something happens then let me know what it does.
Back in the olden days RMs didn't come with a throttle screw. You either raced it or parked it
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Free shipping: VITALMX
Luxon 4-Post Bar Mounts
$189.95 - $239.95
@minton33 @captmoto Yeah they have an idle screw but like I mentioned it’s a PJ so it’s on the choke. And no, no matter what I do with the idle or the air screw I can’t get it to hold an idle.
What does the bike run like otherwise?
The idle screw should go in far enough where it’s lifting the slide high enough that the bike is at a decent rpm. If you can’t do this maybe you have the wrong idle screw?
I would replace the jet block gasket in a carb that old as well. Don’t think it’s your problem but it’s gotta be toast.
Idle on a PJ is on the choke circuit (adjustment is on the choke knob), not what you typically see with an idle screw touching the slide.
Does the choke make any difference in how it runs or starts; can you pull it up just a little and see if it makes a difference? I would pull the carb and take the choke assy out and blow the choke circuit out with compressed air, if it's not open it will never idle correctly, also while you have the choke knob out make sure turning it will make the plunger/needle move up and down.
Have you tried winding the throttle cable out a couple of threads from the throttle housing?
I’ve never messed with one of those. But I’d guess that it’s a problem with the choke plunger or the ports going to the choke are clogged (assuming it has some)
I'd consider upgrading to a more modern Airstriker carb. Anywhere from a 1996 onwards. I currently have a Kehein off an 08 R250 to test on my 1989 but haven't got round to it yet.
The Keheins from 96 onwards have a dedicated idle screw and are just all round better carbs. It should also be a straight swap into your bike. You can pick them up pretty cheap too.
Post a reply to: RM250 wont idle