Bike idles down and dies once it's warmed up

grendel · 05-26-2012, 03:49 PM

THE PROBLEM:
Bike will start fine, then after warming up (usually 3-5 minutes or so), it starts to drop in idle speed, and will eventually die. Once it dies, it will not restart right away unless I open the throttle quite a bit. Best results are had by just waiting a few minutes, and then trying it again.

DONE, ACCORDING TO PREVIOUS OWNER:
- new battery
- new ignition coil
- new spark plug wire and cap
(these all seem to be legit new)

WHAT I'VE DONE:
- replaced head gasket
- replaced air filter
- rebuilt fuel tap
- installed inline fuel filter (fuel shows to be clear as white wine)
- installed correct spark plug (PO had the wrong one in) (looks like it's running a bit rich)
- verified no air leaks on either end of carb (rubber mounts)
- verified that choke is working properly
- tried adjusting idle speed screw
- tried adjusting pilot screw
- tried with fuel tank cap both sealed and open
- adjusted valve clearance (to nearer the top end of spec)
- fresh gas with Seafoam measured in
- oil level is normal (filter is on order so I can change oil/filter to fresh)

KEEP IN MIND:
- this model (near as I can tell) has no fuel pump

=====

I've seen DOZENS of threads about this same problem all over the internet, but most of them end up unsolved (or just were never updated with the solution), so I'm not sure WTF to do. It SEEMS to me that the bike is warming up, and that heat is causing something to fail. I can't imagine that the carb would be affected by being at 'warmed up' temperature, so I've been putting off looking at the carb other than to make sure that it seems to be working (by what you can tell from outside it). One thread advised tapping it in the float area to make sure the float isn't stuck - did that, didn't change anything.

The bike is a 1982 KZ250, but from searching online, this is pretty common no matter the year/manufacturer.

I'm seriously stuck on what to do - thoughts??

gggval · 05-26-2012, 04:10 PM

check for air leaks in the carb manifold. that happened to my bike, and had the EXACT ame simptoms.
good luck!
also could be dirty oil/filter or needs a carb cleaning

Dodsfall · 05-26-2012, 05:27 PM

Have you checked the valve adjustment?

The only other thing that comes to mind is a carb rebuild/thorough cleaning/float adjustment to factory specs.

grendel · 05-27-2012, 07:45 PM

Quote:

Originally Posted by gggval

check for air leaks in the carb manifold. that happened to my bike, and had the EXACT ame simptoms.
good luck!
also could be dirty oil/filter or needs a carb cleaning

Yup, checked for air leaks - everything seems to be normal there.
Oil and filter change are up next. I didn't figure they'd have anything to do with this problem, though, so I just put them on pause - gonna get 'em done soon anyway.

Quote:

Originally Posted by Dodsfall

Have you checked the valve adjustment?

The only other thing that comes to mind is a carb rebuild/thorough cleaning/float adjustment to factory specs.

I checked the valves recently, and they were toward the tighter side of spec (intake was actually out of spec). Both are now adjusted to the higher side within specs. However, it was my first time adjusting valves, so I might not have gotten it perfect - seems pretty simple, though, with the right tool to measure.

gggval · 05-27-2012, 08:15 PM

what happens is gas gets in the oil, so does dirt and bla bla bla. but all that in there scres the oil filter up. please tell me you didn't put new oil in? because there is a reason they do the oil and filter at the sane time.

grendel · 05-27-2012, 10:06 PM

Quote:

Originally Posted by gggval

what happens is gas gets in the oil, so does dirt and bla bla bla. but all that in there scres the oil filter up. please tell me you didn't put new oil in? because there is a reason they do the oil and filter at the sane time.

No, I've only verified that the oil is at an acceptable level using the site glass. I have already bought oil (Shell Rotella 15w40), and it's sitting here ready to go. Just waiting on the filter to come in to my local shop.

For sure, oil and filter will be changed at the same time.

gggval · 05-28-2012, 12:55 AM

im 99% sure its the oil. if the bike has been sitting for a year or more that's its problem.
at least its an easy fix!
goodluck!
have fun!

Castle81 · 05-28-2012, 10:59 PM

I would think a sticking slide in the carb would be far more likely. Especially if it's showing signs of running rich. Heat is not kind to dirty carbs.

grendel · 05-30-2012, 12:05 PM

Thanks for the replies. I'm gonna try to make some headway on your suggestions today.. looks like the constant rain we've been having might actually stay gone today!

gggval · 05-30-2012, 06:08 PM

good luck! post what remedy works

grendel · 05-30-2012, 11:40 PM

Well, I started it up and let it run itself to death (urgh) ... then quickly pulled the plug wire from the plug, attached it to the spare plug I have, grounded it against the engine block, pressed the starter and... nothing.

No pop, no spark. Nothing.

This has me thinking that the suggestions of an electrical heat issue might be onto something...

Bede5man · 06-02-2012, 01:53 AM

Only dies when warmed up...is the choke remaining on???

Is the adjuster up on the bars the choke control?

Too much choke when warmed up MIGHT be able to run it so rich it died at normal temps...

jag13 · 07-14-2012, 10:01 PM

If you start it up and take off, does it kill while riding? Or just while idleing?

Dmurry250 · 07-28-2012, 09:52 PM

I had a similar problem with my bike that i got recently. it was running good then one day it started to run like crap and had to leave the choke on just to keep it running. I cleaned the carbs and put them back together and adjusted best i could without a sync kit. it runs good other than the fact that cylinder four only fires when i'm on the road and its under load. ideas??? seams like a vacuum issue but i'm not sure

05-26-2012, 03:49 PM	#1
grendel Verified Join Date: Feb 2012 Posts: 53	Bike idles down and dies once it's warmed up THE PROBLEM: Bike will start fine, then after warming up (usually 3-5 minutes or so), it starts to drop in idle speed, and will eventually die. Once it dies, it will not restart right away unless I open the throttle quite a bit. Best results are had by just waiting a few minutes, and then trying it again. DONE, ACCORDING TO PREVIOUS OWNER: - new battery - new ignition coil - new spark plug wire and cap (these all seem to be legit new) WHAT I'VE DONE: - replaced head gasket - replaced air filter - rebuilt fuel tap - installed inline fuel filter (fuel shows to be clear as white wine) - installed correct spark plug (PO had the wrong one in) (looks like it's running a bit rich) - verified no air leaks on either end of carb (rubber mounts) - verified that choke is working properly - tried adjusting idle speed screw - tried adjusting pilot screw - tried with fuel tank cap both sealed and open - adjusted valve clearance (to nearer the top end of spec) - fresh gas with Seafoam measured in - oil level is normal (filter is on order so I can change oil/filter to fresh) KEEP IN MIND: - this model (near as I can tell) has no fuel pump ===== I've seen DOZENS of threads about this same problem all over the internet, but most of them end up unsolved (or just were never updated with the solution), so I'm not sure WTF to do. It SEEMS to me that the bike is warming up, and that heat is causing something to fail. I can't imagine that the carb would be affected by being at 'warmed up' temperature, so I've been putting off looking at the carb other than to make sure that it seems to be working (by what you can tell from outside it). One thread advised tapping it in the float area to make sure the float isn't stuck - did that, didn't change anything. The bike is a 1982 KZ250, but from searching online, this is pretty common no matter the year/manufacturer. I'm seriously stuck on what to do - thoughts??

05-26-2012, 05:27 PM	#3
Dodsfall Administrator Join Date: May 2008 Location: Illinois, USA Posts: 15,843	Have you checked the valve adjustment? The only other thing that comes to mind is a carb rebuild/thorough cleaning/float adjustment to factory specs. __________________ 2008 XL1200R To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

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05-26-2012, 04:10 PM	#2
gggval Chris Join Date: Mar 2012 Location: Portland Oregon Posts: 336	check for air leaks in the carb manifold. that happened to my bike, and had the EXACT ame simptoms. good luck! also could be dirty oil/filter or needs a carb cleaning

05-27-2012, 08:15 PM	#5
gggval Chris Join Date: Mar 2012 Location: Portland Oregon Posts: 336	what happens is gas gets in the oil, so does dirt and bla bla bla. but all that in there scres the oil filter up. please tell me you didn't put new oil in? because there is a reason they do the oil and filter at the sane time.

05-28-2012, 12:55 AM	#7
gggval Chris Join Date: Mar 2012 Location: Portland Oregon Posts: 336	im 99% sure its the oil. if the bike has been sitting for a year or more that's its problem. at least its an easy fix! goodluck! have fun!

05-28-2012, 10:59 PM	#8
Castle81 Severed Head Join Date: Jan 2012 Location: White Settlement, TX Posts: 378	I would think a sticking slide in the carb would be far more likely. Especially if it's showing signs of running rich. Heat is not kind to dirty carbs.

05-30-2012, 12:05 PM	#9
grendel Verified Join Date: Feb 2012 Posts: 53	Thanks for the replies. I'm gonna try to make some headway on your suggestions today.. looks like the constant rain we've been having might actually stay gone today!

05-30-2012, 06:08 PM	#10
gggval Chris Join Date: Mar 2012 Location: Portland Oregon Posts: 336	good luck! post what remedy works

05-30-2012, 11:40 PM	#11
grendel Verified Join Date: Feb 2012 Posts: 53	Well, I started it up and let it run itself to death (urgh) ... then quickly pulled the plug wire from the plug, attached it to the spare plug I have, grounded it against the engine block, pressed the starter and... nothing. No pop, no spark. Nothing. This has me thinking that the suggestions of an electrical heat issue might be onto something...

06-02-2012, 01:53 AM	#12
Bede5man Senior Member Join Date: Sep 2010 Location: Baltimore, MD Posts: 339	Only dies when warmed up...is the choke remaining on??? Is the adjuster up on the bars the choke control? Too much choke when warmed up MIGHT be able to run it so rich it died at normal temps...

07-14-2012, 10:01 PM	#13
jag13 Ghost in the machine Join Date: Mar 2008 Location: MN. Posts: 940	If you start it up and take off, does it kill while riding? Or just while idleing?

07-28-2012, 09:52 PM	#14
Dmurry250 Registered Join Date: Jul 2012 Posts: 1	I had a similar problem with my bike that i got recently. it was running good then one day it started to run like crap and had to leave the choke on just to keep it running. I cleaned the carbs and put them back together and adjusted best i could without a sync kit. it runs good other than the fact that cylinder four only fires when i'm on the road and its under load. ideas??? seams like a vacuum issue but i'm not sure