Bike stalls at 2000 rpm and now won’t idle
#1
08-21-2018, 02:14 PM
Bike stalls at 2000 rpm and now won’t idle
So I bought a rough running 2013 KLX 250s with 1500 miles. Owner put on a pipe and didn’t reject it but other wise stock. The main problem was it would die right at 2000 RPMs. I could ham fist it and get it to 3kor higher and slip the clutch to get going like that but if you slowly climb revs or try to hold the throttle at 2k it drops revs immediately and dies.
First thing i did was take take off the pipe. It wasn’t made for this bike and gases escaped at the connection because the carb vent lines and air box were melted. Put the stock one back on and it ran marginally better. I knew there was old gas (~1.5 months old) so I drained it put in new gas. Also changed the oil, new spark plug, and new battery. Still died at 2k
Looked for vacuum leaks with starting fluid and got nothing. Took carb off and it looked clean. One thing that was off was the pilot screw. It was screwed all the way in and pretty tight. Backed it out 1 and 5/8 turns per the manual. Reinstalled and it ran for a little bit. Acted like everything was normal, warmed up, choke off. I revved it past 2k with no problem, it would even hold there with no issue. Dead spot is now at 3k and after about 5-10 minutes it doesn’t want to idle at all.
Checked for leaks again and nothing. Adjusted idle screw and it will idle for a minute or two with no choke and just die. I can adjust it up to 3k to get it to stay running once it’s warm. Cold start with choke on it only gets to 3k. I have to start it with the throttle open now and when it does run sounds not great.
Anything else I should check? Probably gonna get a carb rebuild kit. Pull it and clean it again, adjust pilot to 2.5 turns out. The stock main jet is #118. Is this even a carb issue? Maybe go through the fuel system again. Air box lid is off for now.
First thing i did was take take off the pipe. It wasn’t made for this bike and gases escaped at the connection because the carb vent lines and air box were melted. Put the stock one back on and it ran marginally better. I knew there was old gas (~1.5 months old) so I drained it put in new gas. Also changed the oil, new spark plug, and new battery. Still died at 2k
Looked for vacuum leaks with starting fluid and got nothing. Took carb off and it looked clean. One thing that was off was the pilot screw. It was screwed all the way in and pretty tight. Backed it out 1 and 5/8 turns per the manual. Reinstalled and it ran for a little bit. Acted like everything was normal, warmed up, choke off. I revved it past 2k with no problem, it would even hold there with no issue. Dead spot is now at 3k and after about 5-10 minutes it doesn’t want to idle at all.
Checked for leaks again and nothing. Adjusted idle screw and it will idle for a minute or two with no choke and just die. I can adjust it up to 3k to get it to stay running once it’s warm. Cold start with choke on it only gets to 3k. I have to start it with the throttle open now and when it does run sounds not great.
Anything else I should check? Probably gonna get a carb rebuild kit. Pull it and clean it again, adjust pilot to 2.5 turns out. The stock main jet is #118. Is this even a carb issue? Maybe go through the fuel system again. Air box lid is off for now.
Last edited by Mickeyu422; 08-21-2018 at 03:13 PM.
#2
08-21-2018, 03:38 PM
First, never screw in the idle mix screw tight. It is a needle seat and you can damage the needle or seat.
As for the problem, sounds like a clogged idle mixture circuit. The cross over from idle mix circuit to the slide/needle will be right around 2000-3000 rpm. The carb should be washed out with a carb cleaner or an ultrasonic cleaner to get the passages clean. No need for a rebuild kit since every gasket/seal is reuseable neoprene. We never used rebuild kits when cleaning carbs at the shop where I worked. If you need a single part you buy the single part, much less costly.
For jetting using Kiehin parts check the 250 mods link in my signature. If you use Dyno Jet, KLXter knows them. The stock KLX does need jetted both main and pilot, plus the needle either needs shimmed or swapped out too. But yours has an idle mix circuit problem
As for the problem, sounds like a clogged idle mixture circuit. The cross over from idle mix circuit to the slide/needle will be right around 2000-3000 rpm. The carb should be washed out with a carb cleaner or an ultrasonic cleaner to get the passages clean. No need for a rebuild kit since every gasket/seal is reuseable neoprene. We never used rebuild kits when cleaning carbs at the shop where I worked. If you need a single part you buy the single part, much less costly.
For jetting using Kiehin parts check the 250 mods link in my signature. If you use Dyno Jet, KLXter knows them. The stock KLX does need jetted both main and pilot, plus the needle either needs shimmed or swapped out too. But yours has an idle mix circuit problem
#3
08-21-2018, 05:25 PM
As a follow up to klx678's comments on the idle mixture screw, make sure the idle mixture screw isn't damaged. There have been occasions where the tip has broken off and some times the broken part is stuck in the carb.
Ride on
Brewster
Ride on
Brewster
#4
08-21-2018, 10:26 PM
Thanks for both replies. When you say idle mix screw is that the same as the pilot jet? I should clarify when I adjusted the idle it was with the external thumb screw. Don’t know who screwed the pilot jet in all the way down but it was tight. It also didn’t look broken when I took it out. I’ll check it again seeing as how it sound like I need to do a better cleaning job. Can you give me a better understanding where this idle mix circuit is?
#5
08-21-2018, 11:48 PM
Thanks for both replies. When you say idle mix screw is that the same as the pilot jet? I should clarify when I adjusted the idle it was with the external thumb screw. Don’t know who screwed the pilot jet in all the way down but it was tight. It also didn’t look broken when I took it out. I’ll check it again seeing as how it sound like I need to do a better cleaning job. Can you give me a better understanding where this idle mix circuit is?
https://www.bikebandit.com/oem-parts...4540#sch755258
16014 idle mixture screw
92064 pilot jet
16021 idle speed adjust
Ride on
Brewster
#8
08-22-2018, 02:14 AM
It sounds like you may be using the wrong names in your explanation. The pilot jet and idle mixture screw work in parallel. The pilot jet sets up a course mixture and the screw fine tunes it. To access the pilot jet, the bottom of the carb (bowl) must come off. The idle mixture screw is accessed from the bottom of the carb. From the factory, there is a thin metal plug covering the idle mixture screw, at least on U.S. models for emissions tampering. Is the external thumbscrew you mentioned on the side the carb? That is used to adjust idle speed. It hold the throttle plate slightly open.
https://www.bikebandit.com/oem-parts...4540#sch755258
16014 idle mixture screw
92064 pilot jet
16021 idle speed adjust
Ride on
Brewster
https://www.bikebandit.com/oem-parts...4540#sch755258
16014 idle mixture screw
92064 pilot jet
16021 idle speed adjust
Ride on
Brewster
#9
08-22-2018, 03:01 AM
You would be correct. I’ve been confused. I was talking about 16021 and 92064, the throttle stop and pilot jet. I got the pilot jet mixed up with the pilot air screw. Didn’t even know it existed. I’ll have to pull off the plug that hides it and clean it. Is the pilot jet supposed to be screwed tight and the pilot air screw supposed to be turned out 2.5 turns?
Ride on
Brewster
#10
08-22-2018, 11:24 AM
If you have to go over 3 turns out on the pilot screw the pilot jet is too lean, go up a size or two. If I remember right stock is a 35. At sea level up to a thousand feet or so a 40 works well, over around 3000 feet a 38 works better - less dense air. Some of the jetting information can be found in the cheap mods link in the signature below. D.Pippin provided the information and has a great web site That covers a lot more than just carburetion. I collected a bunch of stuff and put it in a google doc. Pippin has a whole lot more. I have his site linked in the doc. Click on the blue text to get the connection to the link.
I made my document just to propagate the information. You never know when a site may disappear, so it never hurts to make some copies if not copyrighted. I'd definitely invite someone to make a copy of my document and get it up somewhere else. The more the better. Add to them too.
Same with the Marcelino Mod, that is one that should be available in more places when someone does a google search. Well worth having others create Google Drive accounts to propagate good information.
I made my document just to propagate the information. You never know when a site may disappear, so it never hurts to make some copies if not copyrighted. I'd definitely invite someone to make a copy of my document and get it up somewhere else. The more the better. Add to them too.
Same with the Marcelino Mod, that is one that should be available in more places when someone does a google search. Well worth having others create Google Drive accounts to propagate good information.
Last edited by klx678; 08-22-2018 at 11:28 AM.