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Does not respond immediately to the accelerator at highway speed

6K views 20 replies 6 participants last post by  Dicky 
#1 ·
Does not respond immediately to the accelerator at highway speed.
When I travel at highway speed, 60 mph or 4,000 rpm and accelerate, sometimes the engine does not respond immediately, I feel a delay and then it accelerates. I have used additive in gasoline to clean the carburetor and it has not improved. The last time I cleaned and oiled the air filter was in March, at 19,004 miles. Now it has 21,000 miles. I'm going to look at it and clean it again, although my driving is usually on streets and highways and less than 10% off the road. What else could it be?
 
#3 ·
The KLR's carburetor is of the, CV, design. All CV carburetors have an inherent delay between the time the throttle opens and the slide rises.

Given that, "fact-of-life," if your delay still seems excessive, the videos in the, "Carb Overhaul" thread on this website can walk you through a thorough cleaning/adjustment.

Some KLRistas hog out the vacuum transfer port in their slide by drilling it out to a 7/64" diameter. an effort in hope of improving throttle response.

Recommended: "Care and Feeding of the CVK 40," cited on this website, but accessible from Googling.
 
#5 ·
IME, any hole in the throttle slide diaphragm or pinch in the sealing ridge usually prevents speeds above 60 mph, rather than reducing response. But anything is possible.
 
#7 ·
@Dicky,

Your bike is only three years old and it doesn't sit around. You've ridden it quite a bit. At that age and with that mileage your carb shouldn't need service. However, I don't know what the general quality of gas is in Panama.

My takeaway from your opening post is that you have noticed a difference in the way the bike behaves and that it is a bit intermittent.

Using an additive in the fuel should clean things up but it may take time. It may also not treat an issue with the slide if that is the problem.

Given the age of your bike, I am going to assume that you've never had the carb off, so there shouldn't be any mis-assembly issues with it.

If it were my bike I would give the additive a tank or two to do its job, especially if there were no running issues other than throttle response. If it doesn't clear up then I'd rotate the carb so that I could remove the top cover and lift the spring out. Then I'd put my finger in the bore of the slide and gently test for its ability to slide up and down smoothly. I'd inspect the slide and its bore for crud, goo, varnish, evidence of sliding wear that has created burrs, and embedded grit. In short, anything that would inhibit it from sliding up and down freely. Have a look at the diaphragm as well.

Let us know what you find. I do have to note, based upon talking with scores of people who have worked on their own carburetors, that the biggest problem with them is that they do more harm putting it back together than they had when they took it apart. That's why I'm suggesting only a partial disassembly to the part most likely to create a cause and effect. Be very careful with the re-assembly of the slide and cover when you put it back together.
 
#8 ·
@Dicky,

Your bike is only three years old and it doesn't sit around.
Whoa, I'm impressed! How do you know the bike is only three years old--clairvoyant? Seriously, how do you know, secret connections?

The hesitation symptoms that have been described sound like a lean condition. Perhaps there is an air leak around the intake boot? It's easy to inspect the metal-band clamp that connects the intake boot to the carburetor for tightness. Also with the engine running at idle, spraying WD-40 on the boot and especially at the boot to head interface is easy an test to do as well. Any change in idle speed after spraying WD-40 suggests an air leak.

Jason
 
#9 · (Edited)
Another possibility, as Tom posts above: Sticky slide. Slide should move freely up and down when manipulated. Sticking on the way up could cause the "hesitation" experienced, IMHO.

Don't see how a leaky diaphragm causes, "poor gas mileage," as mentioned above. Leaky diaphragm = fuel-lean mixture, IMHO, because needle cannot rise adequately to uncover main jet sufficiently. Not a satisfactory condition by any means, just . . . don't see how the circumstance causes poor fuel mileage. Maybe it does, after all! :)

===========================

EDIT: Acknowledging Tom's previous nomination of the sticky slide; reckon I overlooked the comment or we posted neo-simultaneously! :)
 
#11 ·
Don't see how a leaky diaphragm causes, "poor gas mileage,"...
Yes, it certainly seems counter intuitive.

But back in the early 90s a buddy of mine was experiencing unusually poor gas mileage with his Yamaha Venture that has four CV carbs. We struggled trying to figure out why. But ultimately we discovered several cracked diaphragms and when they were replaced, gas mileage returned to normal.

What's more I've since read on other forums where poor gas mileage was a symptom of a cracked diaphragm.

However, I can't explain the science behind this phenomenon.

Jason
 
#10 ·
Tom,

It seems appropriate to wait for two tanks of gasoline to see the result of the additive. The fuel in Panama is good, besides I only use 95 on the bike. This is how you comment, nobody has touched the carburetor and usually I am afraid of the mechanics, if I am not clear about the diagnosis. LOL. For now I will wait and clean the air filter. I remained pending to comment on the result and the action that I will take after the two tanks.

Thanks to everyone who contributed their opinion.
 
#13 ·
Tom,

It seems appropriate to wait for two tanks of gasoline to see the result of the additive. The fuel in Panama is good, besides I only use 95 on the bike. This is how you comment, nobody has touched the carburetor and usually I am afraid of the mechanics, if I am not clear about the diagnosis. LOL. For now I will wait and clean the air filter. I remained pending to comment on the result and the action that I will take after the two tanks.

Thanks to everyone who contributed their opinion.
Dicky, you mean Clean & Re-Oil your air filter. Correct?

You might check Under the air filter box for any sign of a hole Burnt Thru by a loose exhaust clamp allowing exhaust leakage.
A burn hole would allow dust into the carb throat, which could cause 'sticky slide'. But worse yet, piston, rings, cylinder & valves wear and becomes an oil burner.
 
#14 ·
PDWESTMAN

Of course, clean with kerosene and oil it. I always do it that way, thanks to you in this forum that make so much emphasis on that. I avoid the mistakes of the new owners and I follow all your advice. The verbatim. LOL

I really got a lot out of this forum.
 
#16 ·
Just brainstorming possibilities . . . someone may have monkeyed with the slide spring, as in clipping coils.

Clipping coils changes the initial spring pre-load, but . . . counter-intuitively, clipping coils makes the spring STIFFER (i.e., higher rate, force vs. displacement). Thus, at the higher slide openings (higher throttle positions), the increased spring rate of the compressed spring may resist slide elevation, compared with a stock slide spring configuration.
 
#17 ·
I just serviced the air filter. I attached some pictures of how it was. I am in the first full tank after having applied the carburetor cleaning additive. We have a lot of rain and this weekend is not going to stop. I've only traveled 6 miles.

Bonus, attached the photo of the foot peg scraped on the asphalt.
 

Attachments

#19 ·
Many owners / mechanics totally miss seeing, much less understanding the importance of the cleanliness of those 3 tiny little (transition) holes under the bottom lip of the throttle butterfly plate.
The external adjustable pilot mixture screw outlet & those 3 tiny transition holes all get their fuel from the low speed pilot jet. All four must flow aerosol spray carb cleaner freely.
Use a single strand of wire, bent 90 degrees to poke any foreign particulate Back down out of those holes & flush with aerosol carb cleaner & compressed air.
 
#20 ·
Good afternoon Gentlemen, yesterday I rode the motorcycle for 200 miles. This after having cleaned and oiled the air filter. I even found a small stone in the box where the foam filter goes. After cleaning I had not used the motorcycle until Sunday. Prior to having cleaned the filter I had rolled 35 miles inside the city. Fortunately, the bike worked perfectly and no longer has the delay between the throttle and the engine response. In the whole trip it never happened. I did not touch the carburetor. I only used the cleaning additive in the fuel and then cleaned and oiled the air filter.
I hope this was all.
 
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