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Discussion Starter #1 (Edited)
I have a KLR600 '84 and when the engine is getting warm it runs great all the way to 7k rpm and has power.

But when the engine gets to about half the temp gauge or more, when i start really feeling it on the right leg - it can run normally if you dont rev it over 4k or so - over that, when you give it gas, it stalls for a second or two at a time, stopping and going. It also tends to happen more easily going up a hill. Sometimes the exhaust backfires too when the engine is stuttering.

Any ideas? Could the pilot screw on the carb have anything to do with it?
Thanks!
 

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Sounds like you're describing throttle lag, or slow throttle response.

Slide should move freely, up and down. Diaphragm intact, vacuum port clear.

Don't want to get too involved here ("Care and Feeding of the CVK40" goes far enough), but . . . twisting the throttle grip opens an air valve into the carburetor venturi; the venturi vacuum, piped above the diaphragm, raises the slide and needle. Unless the slide, diaphragm, and needle are all o.k., a temporarily air-rich mixture results, sometimes resulting in the stumble described.

That said, a CV carburetor has an inherent delay between twisting the throttle grip and raising the slide and needle (feeding fuel into the venturi).
 

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Discussion Starter #3 (Edited)
Sounds like you're describing throttle lag, or slow throttle response.

Slide should move freely, up and down. Diaphragm intact, vacuum port clear.

Don't want to get too involved here ("Care and Feeding of the CVK40" goes far enough), but . . . twisting the throttle grip opens an air valve into the carburetor venturi; the venturi vacuum, piped above the diaphragm, raises the slide and needle. Unless the slide, diaphragm, and needle are all o.k., a temporarily air-rich mixture results, sometimes resulting in the stumble described.

That said, a CV carburetor has an inherent delay between twisting the throttle grip and raising the slide and needle (feeding fuel into the venturi).
Thanks for your answer Damocles! I didnt really explain the problem that good, the bike actually stalls over 4k or so (sometimes for couple seconds), it seems like it would turn off if I didnt play with the throttle or change gear. If i kept throttle in the same position the stall would continue and probably it would stop.

What is interesting is that it rides perfectly until the temp gauge gets to about half or more. So I can ride normally, like 20 mins or more with great throttle response up to 7k, and when it gets really hot these problems start and happen almost every time i open the throttle harder, in higher revs (and they are worse up hill).

Only way i can ride it then is below 4k and not opening throttle all the way. And this can go on for hours, it rides great actually but you can just cruise.

So I am thinking it is something temperature specific or perhapse a problem that arises after riding aggresively for some time - not connected to temp??

You mention the vacuum port, could you please explain more? There is a port on top of the carb but it has a cap on it on my klr600, or do you mean something else?
Thanks again!
 

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Hello KLR600

Your problem is a bit of a mystery.

The problem occurring only under load is similar to ignition coil/spark plug lead or faulty spark plug problems. If it were my bike I would be checking the spark plug and Spark plug lead and ignition coil. I would also check other electrical connections, definitely including battery terminals

I would look at electrical causes before I looked at fuel system problems.

In the Trouble Shooting section of the Clymer Workshop Manual under the heading "Poor High Speed Performance" it suggests that some ignition related causes (For Poor High Speed Performance) could be:

"A) Damaged Exciter coil or crankshaft position sensor (Check ignition timing)
B) Damaged CDI Unit"

You need a timing light to check the ignition timing and you need a multimeter to test the crank position sensor. The Clymer Manual gives instructions about how to go about the testing. One way to test the Ignition coil could be to replace it with a second hand one and see if the problem persists

Other members will no doubt have other suggestions about possible causes, most know what they're talking about....

Kind Regards

Matthew
 

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You mention the vacuum port, could you please explain more? There is a port on top of the carb but it has a cap on it on my klr600, or do you mean something else?
Thanks again!
Hole in the slide admitting "vacuum" into the chamber above the diaphragm, under the cap you speak of! :)

Some hog out the hole to 7/64" diameter, in hope of enhancing throttle response time (as did I; satisfactory, but nothing suggesting a productive KLR650 entry into a Grand Prix race).
 

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The fact it movement of throttle/gear impacts it strongly suggests carb. The failing when hot points more to electrical. Having said that sudden electrical problems are probably more common than sudden carb problems - do confusing symptoms.

First thing does the bike have clean fresh fuel? If it's been standing for a long time throw it out and start with fresh fuel.

Then start with the simple stuff. Very first thing I would drain the carb using the drain screw. I have found if you have some water in the float bowl you get symptoms similar to that described - on idle and lower throttle it draws the fuel floating on top of the water, on hard throttle it starts to try and suck up the water as well.

Also check the air filter. If it is blocked badly again you might get similar symptoms, so check and clean that (for a brief trial, a short trial without it will do little harm).

Finally check the tightness of the clamp screw on the carb intake connections in case you have an air leak messing up the mixture.

After that a good carb clean plus a new spark plug at the same time would be my next step. Whatever you do resist fiddling with carburettor settings at this time - if it was running well before it will not have suddenly jumped out of adjustment.

Final step is the changing of major electrical components - fortunately their failure is very rare.

Good luck.

Sent from my Moto G (5S) Plus using Tapatalk
 

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The fact it movement of throttle/gear impacts it strongly suggests carb. The failing when hot points more to electrical. Having said that sudden electrical problems are probably more common than sudden carb problems - do confusing symptoms.

First thing does the bike have clean fresh fuel? If it's been standing for a long time throw it out and start with fresh fuel.

Then start with the simple stuff. Very first thing I would drain the carb using the drain screw. I have found if you have some water in the float bowl you get symptoms similar to that described - on idle and lower throttle it draws the fuel floating on top of the water, on hard throttle it starts to try and suck up the water as well.

Also check the air filter. If it is blocked badly again you might get similar symptoms, so check and clean that (for a brief trial, a short trial without it will do little harm).

Finally check the tightness of the clamp screw on the carb intake connections in case you have an air leak messing up the mixture.

After that a good carb clean plus a new spark plug at the same time would be my next step. Whatever you do resist fiddling with carburettor settings at this time - if it was running well before it will not have suddenly jumped out of adjustment.

Final step is the changing of major electrical components - fortunately their failure is very rare.

Good luck.

Sent from my Moto G (5S) Plus using Tapatalk
All good points, awayonmybike!

You REFRESHED, in my own memory, the consequence of water in the float bowl! I believe (or, at least, believed) the main jet is at the lowest elevation of the carburetor jets. Thus, water--denser than gasoline--compromises fuel delivery from the main jet, as in--at the greater throttle openings. So, running at lower throttle openings, the less-dense fuel may flow through the higher-elevation jets supporting normal operation, but when the throttle is opened, uncovering the main jet, the more-dense water concentrated in the fuel bowl enters the mixture and causes symptoms described.

A possibility; my theory only; contradictions welcomed!
 

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Discussion Starter #8
Thanks for taking the time everyone!

After timberfoots answer i got a new regulator yesterday and been riding the whole day today with no problems!
I was fixated on a possible fuel issue, I forgot to mention I had charging issues too. Also I opened and cleaned the carb and tank couple days ago and the bike has fresh gasoline, the spark plug is new too.

There is one thing though - today is a very cold day in comparison with the last few, it has been raining all night. Im really hoping it was the regulator and not the cold air.
I think the model of the regulator wasnt right when i got the bike - it had 6 "ribs", new one has 8.

Also, I think the stator isnt in good shape. I have seen a video on yt where a guy measures on a running bike between ground on the unplugged stator 6 pin cable and the 3 leads and he gets a reading on all. I dont have a reading between ground and the leads (yellow wires), I get a reading between leads though - all combinations. The video is on KLR650, not sure if that makes a difference. (set to V200~)

And the resistance between leads should be below 0.7 per manual, im reading about 1.2 on all combinations.
 

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If it fits it should be fine. My bike had been running with a one from a completely different Kawasaki for years - they all do the same job, and the KLR alternator output is about the lowest of any bike in their range so it will not overload any regulator

Sent from my Moto G (5S) Plus using Tapatalk
 

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Discussion Starter #10
If it fits it should be fine. My bike had been running with a one from a completely different Kawasaki for years - they all do the same job, and the KLR alternator output is about the lowest of any bike in their range so it will not overload any regulator

Sent from my Moto G (5S) Plus using Tapatalk
I think its for smaller Kawasakis too, still might have been broken though. In any case i got the new one very cheap and now its the right thing so no biggie. I had charging issues and still not sure if the stator is good as well.

But all in all the bike definitely doesnt show any of previous issues, i let the engine get really hot and still no problem, drove for at least half an hour after it was hot. Passed a hill where it always stalls with 6-7k rpm all the way, no stutter at all.

Could the much colder weather make such a difference?
 

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I think its for smaller Kawasakis too, still might have been broken though. In any case i got the new one very cheap and now its the right thing so no biggie. I had charging issues and still not sure if the stator is good as well.

But all in all the bike definitely doesnt show any of previous issues, i let the engine get really hot and still no problem, drove for at least half an hour after it was hot. Passed a hill where it always stalls with 6-7k rpm all the way, no stutter at all.

Could the much colder weather make such a difference?
I believe that tempurature could be at play here.

It is possible that the plastic cap on top of the throttle slide diaphragm is Warped!

Any warpage could allow vacuum to leak during fully warm running and the throttle slide to not fully rise, when you request it.

I'll suggest that you remove, inspect and clean the sealing rib on the diaphragm slide and the groove that it fits in and CHECK the plastic cap for level fitment.
 

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Thanks for taking the time everyone!

After timberfoots answer i got a new regulator yesterday and been riding the whole day today with no problems!
I was fixated on a possible fuel issue, I forgot to mention I had charging issues too. Also I opened and cleaned the carb and tank couple days ago and the bike has fresh gasoline, the spark plug is new too.

There is one thing though - today is a very cold day in comparison with the last few, it has been raining all night. Im really hoping it was the regulator and not the cold air.
I think the model of the regulator wasnt right when i got the bike - it had 6 "ribs", new one has 8.

Also, I think the stator isnt in good shape. I have seen a video on yt where a guy measures on a running bike between ground on the unplugged stator 6 pin cable and the 3 leads and he gets a reading on all. I dont have a reading between ground and the leads (yellow wires), I get a reading between leads though - all combinations. The video is on KLR650, not sure if that makes a difference. (set to V200~)

And the resistance between leads should be below 0.7 per manual, im reading about 1.2 on all combinations.

you should not get continuity from any yellow wires to ground at the stator plug

you should have continuity between all 3 yellow wires in the stator plug.

you could measure a/c volts between the three yellow wires if the engine was running and testing between them.

these are normal readings for a "Y" wound stator config and it sounds like thats what you have, I didnt check, going by why you're saying
 
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