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CVK40 Carb Shim, Pilot Screw, KLX650 needle, slide, 22 cent - KLR650.NET Forums - Your Kawasaki KLR650 Resource! - The Original KLR650 Forum!
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Old 04-04-2008, 01:38 PM   #1
Glenn
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Default CVK40 Carb Shim, Pilot Screw, KLX650 needle, slide, 22 cent

FOR 1987-2015


Here is an explanation on how to shim the carb needle, adjust the low speed circuit (pilot screw), and how to drill the slide (vacuum hole).
The method I describe does NOT require removal of the carburetor and should take most people about 30 minutes to complete.
Why would you want to do these procedures to begin with?
Setting the pilot screw to the proper setting and shimming the carb needle allows for easier starting, it smooths out over-all throttle response, and may add extra horsepower. Drilling the slide lift hole increases throttle response by allowing vacuum to build more quickly. OK, the above is true except for the part about increased horsepower.
Depending on how well your bike was adjusted at the factory, the difference may be quite noticeable.
These procedures will make your bike more responsive and more enjoyable to ride, and that's really what matters.

Let's get started, and please note: Any screws that require removal have RED DOTS on them in the photos.



Settings that I recommend...
  • SHIMMING:
(use "#4" stainless or brass washers)
1 Shim for stock bikes '87-07
2 Shims for aftermarket exhausts '87-07
---------------------------------------
The taper is different on the 2008 needle.
1 Shim for stock and aftermarket exhausts (2008 model)
2 Shims for high flow exhausts (2008 model)


  • FOR PILOT SCREW ADJUSTMENT:
(Recommended for all years 1987-2008. Setting is from fully seated.)
1.75 turns for a stock KLR650
2 to 2-1/4 turns for most aftermarket exhausts
2-1/2 turns for high flow "straight through" exhausts







PILOT SCREW ADJUSTMENT:
1. Loosen both clamps on the carburetor
2. Remove throttle cable bracket and undo cables
3. Loosen choke cable adjuster for slack and gently pull the metal end (CIRCLED RED) from the plastic fitting (OR remove fitting from carb)
4. Rotate carburetor clock-wise (top is closest to exhaust)
5. Use a small drill bit to just barely penetrate the protective plug (woodscrew to extract it if necessary)
6. Turn the screw inward until gently seated, then turn out to the desired setting
7. Rotate carburetor back in place
8. Verify choke cable is inside the plastic fitting
9. Tighten clamps on carburetor
10. Reinstall throttle cables and support
11. Re-adjust choke and check for proper operation





SLIDE DRILLING:
(continued from step 4 of PILOT SCREW ADJUSTMENT)
5. Remove the four screws from the black cap on the carburetor
6. Remove the vacuum slide (carb needle is removed with it)
7. Using a 7/64 drill bit enlarge the OUTSIDE hole (circled in blue)
8. Remove all metal shavings and reinsert needle assembly
9. Line up the needle and reinstall slide into the carburetor
10. Carefully reinstall the black cap, do-not pinch the diaphragm
11. Rotate carburetor back in place
12. Verify choke cable is inside the plastic fitting
13. Tighten clamps on carburetor
14. Reinstall throttle cables and support
15. Re-adjust choke and check for proper operation
NOTE: When drilling the slide lift hole (blue circle) use a 7/64" bit.
Do-not drill it larger than that.





NEEDLE SHIMMING:
(continued from step 6 of SLIDE DRILLING)
7. With the slide removed, separate the needle from the slide
8. Install desired number of shims under the needle
9. Reinstall needle in the slide
10. Line up the needle and reinstall slide into the carburetor
11. Carefully reinstall the black cap, do-not pinch the diaphragm
12. Rotate carburetor back in place
13. Verify choke cable is inside the plastic fitting
14. Tighten clamps on carburetor
15. Reinstall throttle cables and support
16. Re-adjust choke and check for proper operation


I hope this helps clarify the procedures for some of y'all.
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Old 04-04-2008, 01:51 PM   #2
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Thanks Glenn. I've been wanting to do these mods.

Bringing them all together was a great idea. I'll let you know how it goes.
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Old 04-04-2008, 02:58 PM   #3
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

I purchased a pack of mixed neoprene washers from Radio Shack. They didn't have any metal ones. Is there any problem with using these type of washers?
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Old 04-04-2008, 03:20 PM   #4
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Quote:
Originally Posted by spook View Post
I purchased a pack of mixed neoprene washers from Radio Shack. They didn't have any metal ones. Is there any problem with using these type of washers?
I am not sure, they may be too thick, try ONE. Stainless shims are usually around .025"
I'm not sure how thick the brass ones are that I used, but they should be comparible to the stainless.

Try one shim, adjust the pilot, and see how well it runs.
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Old 04-05-2008, 12:39 PM   #5
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Quote:
Originally Posted by spook View Post
I purchased a pack of mixed neoprene washers from Radio Shack. They didn't have any metal ones. Is there any problem with using these type of washers?

Rona has stainless ones.
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Old 04-12-2008, 03:00 AM   #6
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

All I could find at lowe's was a # 6 washer. Is this too large to work ? Hopefully I can track a # 4 down tomorrow.
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Old 04-12-2008, 06:11 PM   #7
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Okay, here is what I found at ace hardware. It's a # 4 brass washer. Think there will be any problems using this ? Also, one seems a bit thicker than the other. I don't have any way to measure either . The thicker one looks more uniform though.
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Old 04-12-2008, 10:03 PM   #8
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

How do these mods compare to an actual jet kit?
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Old 04-13-2008, 02:07 AM   #9
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

That washer is ok to use, but do you need two shims?
Shimming and adjusting the low speed screw is a good alternative to a jet kit. Most jet kits require a lot of tuning to get dialed in. A better alternative is a KLX needle. You can find info by searching for KLX needle.

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Old 04-13-2008, 08:29 PM   #10
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Sorry , I should have been more clear. I understand I need only 1 washer with my stock KLR etc . I was curious as to which washer I should go with- notice in the pic there are 2 washers side by side- , one seems a bit thicker than the other and I don't have a way to measure them. Prob. no big deal. I'll prob go with the thicker washer because it seems more uniform than the other. Let me know what you think though.

p.s. - These are both # 4 washers, brass etc.
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Old 04-13-2008, 10:04 PM   #11
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Quote:
Originally Posted by deadjed View Post
Sorry , I should have been more clear. I understand I need only 1 washer with my stock KLR etc . I was curious as to which washer I should go with- notice in the pic there are 2 washers side by side- , one seems a bit thicker than the other and I don't have a way to measure them. Prob. no big deal. I'll prob go with the thicker washer because it seems more uniform than the other. Let me know what you think though.

p.s. - These are both # 4 washers, brass etc.
What exhaust are you running?
If stock, use the slimmer one. If aftermarket use the thicker one. I think that is an inconsistency in the manufacturing process, they normally aren't that thick. Though it is thinner than 2 shims, so it is a good compromise.

EDIT: Saw where you said it is stock. Use the regular #4 (thinner)
Adjust the pilot screw also, and you are in business! You'll notice how much smoother it is afterward.
If drilling the slide you'll notice faster throttle response as well.
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Old 04-14-2008, 12:05 AM   #12
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Thank you. I can't wait to do these mods. I'm going to put a new spark plug in too while I'm at it.
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Old 04-14-2008, 11:25 AM   #13
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Thanks for the post! I finally got these mods done and what a difference!
FYI, the carb shimming and it only cost 14 cents for the #4 brass washer at Ace Hardware for me!

I also spun the carb half way and adjusted the mixture screw. The plug didn't need to be drilled out as it just wasn't there!?? Thats ok, and good for me! I found the stock setting was 1 1/8 turns so that easily explained the popping on deceleration! That 1.75 turns is great with the "L" mod and a K+N filter!
Can't believe how easy it is to work on this bike! Did I mention how much better it runs now? Plan to get the progressive springs installed next weekend. Will check the posts for the best practice on this and then on with the dunlop 606's and out on the trails!!!! The bike is actually much more trail worthy now!

Thanks to all the awesome write ups on this site!
The KLR650.net team is the place to go to setup this bike for best performance indeed as you know these bikes inside and out!
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Old 04-25-2008, 09:47 AM   #14
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

thanks for posting this, I was very curious as to what the carb shim mod was and how to do it. this is fantastic!
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Old 04-28-2008, 05:38 PM   #15
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Quote:
Originally Posted by Tepnr View Post
How do these mods compare to an actual jet kit?
will changing the Jet be the equivelant to drilling the slide and shimming the needle? i was going to do the carb shim mod, but i will be purchasing a new muffler soon and will jet the carb for that reason. i already turned out the pilot screw.
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Old 04-28-2008, 05:41 PM   #16
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

You do-not need to goto a larger jet. Shimming the needle is what richens the mixture, drilling the slide lift hole allows for faster throttle response.
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Old 04-28-2008, 11:12 PM   #17
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

even with a supertrapp race pipe?
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Old 05-07-2008, 02:31 AM   #18
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Silly question, drill bit size as quoted 7/64" ,shims 4". I think here in South Africa we use millimeters, does this 7/64" refer to inches struggling to convert to millimeters
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Old 05-07-2008, 02:47 AM   #19
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Gday,

We use millimetres too. In metric, 7/64'' (inches) is 2.778mm to be precise, the closest drill would then be 2.8mm. However, even in metric countries, you should be able to readily buy imperial sizes from your hardware. Varying even the slightest when it comes to carb's can be bad.
Alternatively, if you can get a hold of 'numbered drillbits' a number35 drill is 2.794mm and a number36 is 2.708.
But do try to grab the 7/64''. Hope this helps the metric blokes!

Cheers,
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Old 05-07-2008, 02:54 AM   #20
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Default Re: Carb Shimming, Pilot Screw Adjustment, Slide Drilling

Thanks allot, will import the dill if need be. what size should the shim be in mm
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