Jump to content
Sign in to follow this  

Help: Hanging Idle

Recommended Posts

Ok, before you search nazi me, I've searched, tried all the advice I found, maybe I missed something.

Idle is set correctly as far as I can tell. 70 or 72 Leak jet (I think), 172 Main, 40 pilot, 800 ft asl.

If there is a load on the engine it will drop to a normal idle speed. But, if you give it gas it will hang for what seems like eternity and the only way it will go down is if you give it load again.

Thank you

Edit: Could it be due to too much throttle cable slack? As mine has been on the loose side recently. Not used to the push-pull system

Share this post


Link to post
Share on other sites

When I got my YZ250F it would do the same thing. So I adjusted the idle to as low as it could go without it dieing. Then adjusted my fuel screw to where the engine would idle the best and bogged the least. Then turned up my idle alittle bit more. But I also had to clean my carb especially the PAJ.

Share this post


Link to post
Share on other sites

As far as the throttle cable goes just make sure the throttle lever is going back to the rest position when you let off the throttle. Have you tried adjusting the pilot screw? A lean pilot circuit will cause a hanging idle. And like Gray said...check you valves.

Share this post


Link to post
Share on other sites

Hanging idle is usually a lean condition in the pilot circuit. Open your fuel screw in 1/4 turn increments until it improves. If you get more than 3 turns from fully seated, then go to a 42 pilot jet, reset the fuel screw to 3/4 turn open, and begin adjusting again.

If this doesn't fix it, you may have a leak in the intake tract somewhere. Make sure your hose clamps are tight, and there are no cracks in the boot. After you've done the easy stuff, if it STILL hangs, then check the valves like gray sez.

Share this post


Link to post
Share on other sites

Changing the pilot jet should only be necessary if something has been changed to make the original jetting wrong, such as a new exhaust system, cams, or moving from Colorado to Kansas. If the bike ran OK once where it is, and with the current equipment, don't change the jetting until you have ruled out a transient condition.

Troubleshoot in the following order (each step assumes the previous one did not correct the problem):

> Check for obvious sources of air leaks (loose clamps, missing hoses). Use a carb cleaner spray like Berryman's B12 to spray around suspect areas, but watch out for sources of ignition!

> Adjust the idle mixture and speed. If it cannot be corrected by backing out two full turns, there is something wrong. If it can be corrected AND stay corrected by backing out to around 3 - 3 1/2 turns, there might be a case for re-jetting, or carb cleaning, but don't go there yet.

> Check for less obvious sources of air leaks.

> Check the valve clearance.

> Pull the carb apart and try cleaning it thoroughly.

If none of this accomplishes anything, changing the pilot jet may be a good next step.

Share this post


Link to post
Share on other sites

Yeah, gray I agree that a pilot jet change may not be in order if the bike previously ran well. I just saw that he is running a 40 pilot, and I had to go up to a 42 when I first got the bike, as the 40 was too lean. He also runs at an altitude similar to mine.

I think you're spot on in the steps above. I was just making the point that in my opinion, it often pays to check the easy things first.

Share this post


Link to post
Share on other sites

You do have a point about the pilot jet. That's smaller than standard, I believe, and as I think of Ohio, I'm not sure where he would be that he requires one that lean. So if indeed, he just bought the bike from some remote location, that could well be the problem.

It's still probably wise to go through the steps I laid out in order, but the #40 jet is suspicious, now that you mention it.

Share this post


Link to post
Share on other sites
You do have a point about the pilot jet. That's smaller than standard, I believe, and as I think of Ohio, I'm not sure where he would be that he requires one that lean. So if indeed, he just bought the bike from some remote location, that could well be the problem.

It's still probably wise to go through the steps I laid out in order, but the #40 jet is suspicious, now that you mention it.

Cincinnati, Ohio (20 Miles N) Bought it in Middletown (another 20 miles). I have a 40 and a 42 PJ kickin around. Should I try the 42? Had the bike for a year, developed this problem, maybe 4 months ago.

Share this post


Link to post
Share on other sites
Cincinnati, Ohio (20 Miles N) Bought it in Middletown (another 20 miles). I have a 40 and a 42 PJ kickin around. Should I try the 42? Had the bike for a year, developed this problem, maybe 4 months ago.
Troubleshooting steps are usually laid out in the manner that they are to keep you from chasing your tail around blind corners. If you end up having checked all the stuff on the list and still have the same problem, then yes, by all means try it. But if you have tight intakes or a shrunken carb isolator, you could still "fix" the problem with a bigger jet, but you would still have the same problem, sort of like painting over rust.

Share this post


Link to post
Share on other sites
Troubleshooting steps are usually laid out in the manner that they are to keep you from chasing your tail around blind corners. If you end up having checked all the stuff on the list and still have the same problem, then yes, by all means try it. But if you have tight intakes or a shrunken carb isolator, you could still "fix" the problem with a bigger jet, but you would still have the same problem, sort of like painting over rust.

Gray and everyone, thanks tons for this help! :banghead: I will get around to troubleshooting this weekend, and I'll post what happens.

Share this post


Link to post
Share on other sites

It's great to have all this help on these forums but please make sure you post the results of the fix so we can all learn and make life just that little bit easier next time.

Cheers from DownUnder

Share this post


Link to post
Share on other sites

Ok. Little update, tried adjusting the fuel screw with the 40, still there, tried with the 42, still there (but it idled normally after some time). I was relfecting the other night and realised that this problem started shortly after I had raised the needle 1 position. I am going to try dropping it 1 position. I will check valves when I receive my radiator guards.

Share this post


Link to post
Share on other sites

Thanks to you guys for this post. I rode my WR for the first time in several months last week and found I had this hanging idle... again. I fixed it last by time by inspecting everything and found a frayed throttle cable. I replaced the pair and the problem went away. I haven't dug into the problem again, but will check for leaks etc as advised. I can't imagine the throttle cables are frayed again. Thx.

Share this post


Link to post
Share on other sites

Update!

So today I tore in to have a looksy at the valves. First I check the boot for leaks and washed both the boot and airbox.

I hope I lined up the engine right... the little "HI" mark was in the small window.

With that in mind, here are my findings:

Right Intake: .1-.12mm

Middle Intake: >.1mm

Left Intake .1-.12mm

Exhausts are still in spec.

Thanks

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...