KLR600 misfiring
 

I have a KLR600 '87. Following an engine rebuilt it ran fine with plenty of power. Now it starts missing at around 4500 revs and won't rev any higher than 5000. It also backfires badly when I rev then let the throttle off. I have changed the CDI and carb pin and spark but these have not made any difference.

I'd be grateful if anyone has any ideas about this problem and also about what parts I might get to solve it. Could it be a value problem?

The bike lives in Kenya and I'm in the UK so I need to take any parts with me next time I go there as I can't get anything for it once there.

Thanks
Christian

Hi there,
i had a similar problem after a carb rebuild in which i changed the float height. the remedy was to reduce the height of the float (i.e. more fuel in chamber before cutting off fuel supply).
hope this helps,
bal

Sounds like a complete cleaning of the carb may be in order especially if the bike has sat for a long time.
Also, I'm not sure if the KLR 600 has a vacuum actuated petcock, but the diaphram could use a look if it has one.
Good luck,
Rod

Many thanks. Carb problem seems to be the consensus. Would the backfire likely be part of the same problem? I have a hazy idea that backfiring happens when the mixture is ignited too late or something.....

Christian

From the backfiring I take it that there is one cause which might be a leaking needle valve. Make sure that the little spring damper inside the needle moves freely as otherwise the needle might leak only when the bike is running / vibrating. The backfiring is usually caused by the engine running too rich when you close the throttle and the bike is "pushing".
You can cut out the float position as this would have caused problems from word go. Leaves a faulty or sticking float needle valve or just dirt in your carb for a cause.
Ignition problems on CDI bikes are extremely rare. Sometimes they just die. (Popped capacitor) Very rarely they have temperature related problems with broken soldering on the circuit board.

Thanks Lecap.

So if I were to get parts in the UK to take out to the bike, spring damper, needle valve and diaphragm might help (the needle is new already). Anything else other than a good clean of the carb?

As I failed to mention earlier the bike starts, idles and runs at low revs perfectly.

Cheers
Xtian

Don't worry about the diaphagm. If it would be torn you would not get anywhere near 4500 rpm. The spring loaded damper is a little pin on the reverse side of the float valve needle. The float valve needle comes as one and if you replaced it it should be fine. If the damper in the needle is stuck a good wash of the needle with carb cleaner usually does the job.

Make sure you have the correct spark plug.

Make sure your air filter is clean and intact.

Also clean the carb nicely as they accumulate a lot of gunk around the diaphagm and slide over the years.

Take a diaphram and carry it as a spare if nothing else...