KLR 650 runs well for a while then seems to miss fire

[Shanti]

Hi There , i seem to having problems with my KLR 650 , when i get out on the open road and after riding for about half an hour or so the bike starts to miss fire and surges , feels like a fuel problem but when fuel is checked all is ok , i had this problem once before on a long ride and found my headlight wasn't working so when i replaced the fuse ( i guess the same fuse controls the CDI unit ) all was ok , now yet again this problem has manifest but the fuse is ok , on one long ride i kept stopping then would drain the carb and this seemed to help but i suspect the cooling down was helping when i stopped more than my tinkering , what do you think could be the problem ?

[markharf]

Is your problem related to the weather? I've recently had a similar issue on my 2007 KLR (about 50k miles). In my case, stopping (with or without shutting off the engine, like for a traffic light or two) cures the stumble/misfire temporarily. The longer I stop, the longer the cure, but it starts up again after 2-25 miles. It isn't affected by venting the tank---stopping for just long enough to open the cap doesn't work, but stopping for 5 minutes to cuss and moan without taking any sort of constructive action does.

For better or worse, this was happening in hot weather last week--95 F/35 C with high humidity. Now that it's cooled off, I can't get the problem to happen at all, even under load up steep grades. So I'm taking off into Mexico, fully expecting to be incapacitated next time I hit serious heat. The alternative is to hang around forever, talking to mechanics and posing questions on internet forums.

The main suggestions aside from the obvious checking of jets, spark, petcock and the like, have involved vapor lock or heat-related electronics. I don't have a spare coil, or I'd try it out. I am now carrying some foil insulating tape and will start plastering it all over fuel lines and anything else that looks vulnerable to heat-induced malfunction if and when my problem recurs.

I did also use some sort of mystery miracle stuff in my last tank of gas on the recommendation of a dealership mechanic. He suspected carbon buildup in the top end and said this stuff would deal with it. I suspect over-eagerness to get me out the door and on to the next mechanic....but what do I know? Another guy said all his similar problems vanished when he finally found the tiny holes in his carb diaphragm on the third inspection...but I think I'm done taking my carburator apart for a little while, at least.

Hope that's helpful. Please post here if you do diagnose a lasting solution.

Mark

[Sjoerd Bakker]

Misfiring and dying while it is hot weather and when engine warms up after some running time ; NO problem when weather is cold.

Sounds like it may be CDI related . Had a simillar problem once with a Suzuki GS 550 which would suddenly stutter and die after running warm, then after cooling off 10-15minutes would start back up.Sold it. Just recently my GS 1100 came down with it after 250 000 km , -- several times just dropped dead at a stoplight after summer in-city riding where cooling was not optimum. After a half hour it would refire again, not a good thing to have on a tour.
In the BMW case it was found to be the small ignition pickup magnet set which signals the CDI unit.Problem was solved by installation of a new pick-up unit.
The KLR may now be having similar problem- misfire when hot, good when cooled down ,until hot again. Just a suggestion.

[kalispell365]

do you have an inline fuel filter?
this will cause your symptoms,whether its vapor lock,or lack of a good flow of fuel because of the filter,i dont know.
this problem is well documented elsewhere.the bike already has filters in the tank,no need for aftermarket additional filter.

[markharf]

I can't speak for the OP, but I added an inline filter only after this problem began, now 2000 miles ago. I'm aware of the theory that says you don't need one, but hey, it's easily accomplished and easily discarded if it proves a problem.

The possibillity of a heat-sensitive CDI gives me bad dreams. No way to test it, since the issue arises only under way in brutally hot weather. No apparent way to get it warrantied. In fact, no obvious way to get ahold of one now that I'm headed south.

Part of what I find most puzzling is that the misfire doesn't only go away due to the engine cooling off. It also goes away when I stop to wait for a traffic light, which sends the engine temperature even higher. I find this aspect inexplicable....but that's not unusual.

Thanks (from me) for responses. Hope the OP chimes back in.

Mark

[Shanti]

Had an in-line filter , on the first time i had this problem soaked a cloth and wrapped it around the in-line filter , this seemed to work for a while , again maybe it is just the stopping to do this that was helping , decided to remove the in-line filter altogether , the problem still continues , my instinct keeps looking at the cdi unit , is this a common problem on the KLR ?

[nath23]

I had a similar problem to this on my kle 500 recently. it kept dying on me after half hour or so and would restart and run fine after a breather. i turned out to be one of the breather pipes to the carb was getting squashed by the seat and blocked. you could check your breather pipes and make sure it is getting enough air.
hope it turns out to be this simple.
regards
Nathan.

[liketoride2]

I had a similar but not identical problem once which progressed in about 50 miles from missing at speed to not running at all off idle, this being in a remote area with no source of help available. Out of desperation, or ignorance ), I drained the float bowl and that totally solved the problem, and I have no notion why unless it was a sticking float valve (tapping on the float bowl hadn't helped). It may seem silly, but after that experience I would recommend trying it to anyone having possible fuel delivery problems with a KLR 650, and also recommend carrying the correct sized Allen wrench to do this in your KLR. Upon another occasion I also had a problem related to an in-line fuel filter, as others have described, but had removed the filter before the above detailed episode occurred.

I know this doesn't directly relate to the problem described in Shanti's original post because upon one occasion he repeatedly drained the float bowl, but thought I would mention it for general information.

Good luck.

Mike
Idaho
Ride Around the World 2005

[Shanti]

thanks for the help , all my looking has gotten me to the exciter coil and the CDI unit , going to try test them when this problem manifests next

[markharf]

Coil andd CDI have been a concern all along for me, but the problem has been so short-lived that I'm not sure how I'd test either one. When I stop, the problem goes away. But I'm glad you're making progress, and hope you post back here if you ever do come up with a solution.

I couldn't get my bike to manifest the problem once temperatures dropped below 95F/35C or so. Even chugging uphill in gravel and sand (6000 vertical feet out of Copper Canyon) or blasting up long highway grades wherever I could find them didn't phase my bike, so I'm resigned to having the problem return once I can't avoid hot weather any more. This should happen someday soon--maybe Panama, maybe Nicaragua.... Probably, an intelligent, forward-thinking rider would have at least brought the parts along, if not changed them out pre-emptively.

enjoy,

Mark

[jimmy101]

I have had many a bike do that. Apart from minor fueling issues like clogged fuel filters etc, it was either:

1. running rich and plugs fouling when hot (as hot = richer), and or more likely:
2. sparky lead has a crack somewhere and is discharging/earthing out somewhere. This always is noticeable as engine gets hotter.
I don't believe the "hot" cdi issue - more likely faulty ignition system down from that (coils/leads) or even pickup sensor. Sometimes even the spark plugs are dying as it gets worse with heat.

[Shanti]

Thanks for all the help , I think I have found the problem , was riding up to Knysna in South Africa and because fuel stops are quite frequent I didn't fill the tank , bike rode like a dream , then had a look around and came across a mod called the hurricane mod which essentially is removing the innards from the petcock , seems this problem is common to KLR that a vacuum is formed by the vacuum pipe that goes from the petcock to the carb gets hot and bends restricting air through it causing fuel starvation and thus my problem , will keep everyone posted as to the results and thanks again

[markharf]

Hmmmm. Interesting, and first I've heard of this....but I have checked for bent, crumpled or kinked petcock-related hoses. It's easy to kink a hose when you're messing with your carb and petcock (on a hot day, sweating copiously and late for wherever you're going).

So when you say "removing the innards," what does that involve? What's the stated purpose of petcock "innards?" In other words, what's the downside?

I had my first hint of a repeat of my earlier trouble last week in 100 (F)/upper 30's (C) degree heat in lowland Brazil. I finally got to plastering reflective heat tape all over my fuel lines and the bottom of my carb, all of which sit in the full heat of the engine. But then I gained some altitude and it got rainy and chilly, so who knows?

Mark

(from Ouro Preto, wet and gorgeous)

[dlh62c]

Don't neglect the ignition.

My 640 failed to run and it was the ignition. The bike would bog and stall when rolling on the throttle. I was dead set on tearing into the carburetor thinking it was the problem. Trimming 1/4 off the ignition wire and reattaching it to the spark plug connector was the fix.

The below paragraph came from this site: Dan's Motorcycle "Electronic Ignition".

Carburetion can cause a miss that looks, acts, and feels exactly like an ignition miss. How do you tell the difference ? Easy, Hook up a timing light. Use one of the types that does not have to be hooked to a battery for power, if possible. A lot of the old style lights were like this. Tape it to your handlebars and go for a ride. Look at the light. If the light looks bright and steady when the misfire occurs, then the problem is in Carburetion. If it goes out when the misfire occurs, then the problem is with the ignition. There are all kinds of ways of doing this and you can use different tools, like plug caps with lights on them. The big thing is being able to see when the spark occurs... or doesn't occur.

I'm sourcing parts now for a light setup to help me isolate between carburetion and ignition problems in the future.
http://www.amazon.com/Lisle-20610-In...2619906&sr=1-1
http://www.amazon.com/Thexton-404-Ad...xgy_auto_img_a

Could there be more than one problem?

Good Luck!

daryl

[dlh62c]

One more thing...make sure the fuels lines are secure. If not, air can be drawn into the lines resulting in fuel starvation. I've seen this myself and the fuel line connections were not leaking fuel.

daryl