Missing at high RPM. Need help - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 19 Old 12-15-2010, 11:20 AM Thread Starter
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Missing at high RPM. Need help

I bought this 1998 KLR about a month and a half ago. From the first time I tried to really wrap it out, it starts missing in 3rd, 4th and 5th between 4500 and 5500. It has a jet kit with a Supertrapp exhaust and an aftermarket filter. I've tried replacing the petcock, fuel lines, vacuum lines and I even replace the coil. I can't get it to run smoothly under hard acceleration. It still coughs at 4500 to 5500 RPM in 3rd,4th, and 5th. I can accelerate hard from 1st to 2nd and it will be smooth up to 7500 rpm. I took off the carburetor and cleaned it with carb cleaner. Nothing has worked so far. I would appreciate some insight. Thanks.

FEO
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post #2 of 19 Old 12-15-2010, 02:55 PM
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Originally Posted by feo350 View Post
I bought this 1998 KLR about a month and a half ago. From the first time I tried to really wrap it out, it starts missing in 3rd, 4th and 5th between 4500 and 5500. It has a jet kit with a Supertrapp exhaust and an aftermarket filter. I've tried replacing the petcock, fuel lines, vacuum lines and I even replace the coil. I can't get it to run smoothly under hard acceleration. It still coughs at 4500 to 5500 RPM in 3rd,4th, and 5th. I can accelerate hard from 1st to 2nd and it will be smooth up to 7500 rpm. I took off the carburetor and cleaned it with carb cleaner. Nothing has worked so far. I would appreciate some insight. Thanks.

Hmm...

I'm thinking that you do have a carb problem. Where is the throttle postion when you get the missing? Probably in 1st and 2nd you are going through the spot so fast you don't notice the problem.

Motorcycle carbs work on throttle postion not RPM. You'll be in the needle to main jet transtion at 1/2-3/4 throttle. Look at the sizes of the main and needle jet. Check the needle itself be sure it's seated right and not damaged. Usually it's better to put everthing back to stock and go from there. How's the plug look, it will give you an overall indication of mixture.

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9

Last edited by Spec; 12-15-2010 at 03:01 PM.
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post #3 of 19 Old 12-15-2010, 03:04 PM Thread Starter
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It happens at full throttle. The carb has been jetted. It is on the medium jet that comes with the kit. Could I be reaching a lean situation at this area? Should I try the bigger jet?

FEO
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post #4 of 19 Old 12-15-2010, 04:17 PM
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Originally Posted by feo350 View Post
It happens at full throttle. The carb has been jetted. It is on the medium jet that comes with the kit. Could I be reaching a lean situation at this area? Should I try the bigger jet?

It's hard to diagnose virtually... when you say it coughs what do you mean? If it feels like the motor can't keep up with the throttle, "bogs" is the term I would use it's too rich. If the motor suddenly surges in a certain area that would indicate a lean condition.

In the rpm range you mentioned 4500-5500 my bike is at 3/4 throttle (4th and 5th gear) right where it transtions onto the main jet. If the needle taper/height is too aburpt the transtion won't be right. Does it have the stock needle in it? if so does it have any washers on it (for the .22 mod)? Is it seated right on the slide's plastic deal (technical term!)? Bike Bandit 1998 KLR fiche look at the carb section make sure your sis put together right.

You need to research the jet kit you have and see how it compares to stock. Maybe the last owner put the wrong kit in it? What does the plug look like?

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9
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post #5 of 19 Old 12-15-2010, 04:48 PM
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Throw a new spark plug in 'er an see what happens.

NGK DPR8EA-9. Kind of important to get that one. Around 3 bucks. We can hold a bake sale if you need an assist. You may very well have carburetor problems, yet I have an inkling the wrong or fouled plug may be an issue. A weak or colder plug may not be strong enough to burn the full load at higher rpm

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[/I]
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post #6 of 19 Old 12-16-2010, 08:16 AM Thread Starter
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It surges and everyone has told me that it feels like a lean condition. The needle did come with the kit and has different heights. If I adjust the needle what direction do you suggest I go? I am assuming I need to pull it up a notch to allow more fuel. I have done minimal work on carburetors and could use all the help I can get. And I replaced the plug early on and the plug that was in it was perfectly fine with normal wear.

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post #7 of 19 Old 12-16-2010, 08:18 AM Thread Starter
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No need for the bake sale. The spark plug was one of the first things I replaced. The plug that was in it was perfectly fine with normal wear. I think I may have to tear into the carburetor.

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post #8 of 19 Old 12-16-2010, 08:53 AM
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I would put the carb back to stock specs so I would have a reference point

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post #9 of 19 Old 12-16-2010, 09:03 AM Thread Starter
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I will try that, but isn't there something that is drilled out when you install a jet kit? Won't this have an effect if I put in the stock jet and needle?

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post #10 of 19 Old 12-16-2010, 09:37 AM
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Quote:
Originally Posted by feo350 View Post
No need for the bake sale. The spark plug was one of the first things I replaced. The plug that was in it was perfectly fine with normal wear. I think I may have to tear into the carburetor.
Good to know about the plug. You hadn't mentioned that you replaced it. You did specify a miss at high RPM's. Now you describe a surge. They are different, and can have different origins. Surging implies carburetor issues to me. A dead miss at high RPM's does not.

The perfectly good plug you removed should answer your questions in a general way as to whether the bike is running rich or lean by the coloration.

Surging can be attributed to any of a number of things.....how long has that SuperTrapp muffler been on there, and what is the condition of the packing? Have you thoroughly inspected your drive chain for wear? Chain problems will surface in higher gears and at higher speeds more than in low gears at higher RPM's. Some aftermarket air cleaners do not seal well, creating intermittent lean conditions. Restricted exhaust can cause rich conditions.

Did this bike ever run well in it's current exhaust / air cleaner / carburetor jetted state? What I mean is, did the bike run well, and develop these surging issues, or did someone mess it up, and you are trying to straighten it out?

The spark plug you took out has a story to tell you may not be able to put into words.

******
“many a trip continues long after movement in time and space have ceased”- Steinbeck, [I]"Travels with Charlie"
[/I]
[IMG]http://i718.photobucket.com/albums/ww187/vatrader01/KLR%20mechanical/04e28c5e.jpg[/IMG]

[FONT="Century Gothic"][I]Sometimes your only available transportation is a leap of faith[/I] [/FONT]
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