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Old 09-06-2012, 07:41 AM   #3826
redog1
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+1

Quote:
Originally Posted by XDragRacer View Post
Maybe, except . . . the pilot (or, "fuel") screw dominates only the pilot, or idle carburetor circuit. At mid-throttle, the needle and the needle jet dominate the air/fuel mixture.

http://www.gadgetjq.com/keihin_carb.htm

Shimming the needle, fuel-enriching the mid-range carburetor mixture, may be more effective addressing mid-throttle performance than adjusting the fuel screw. (Fuel screw adjustment a good idea, regardless; 1.75 turns out as a starting point for stock engines.)

EDIT: Please disregard comment opposing ADW's suggestion above; I misread "mild throttle" for "mid-throttle." ADW's approach, adjusting fuel screw addressing mild throttle surge, seems perfectly sound.


.
Idle mixture screw only effects the air/fuel mixture at idle (off throttle). Adjusting it a little richer will cure a lean backfire/pop on decelleration and possibly smooth out your idle.
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Old 09-06-2012, 08:31 AM   #3827
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.22 mod will certainly help with MID throttle surging but according to my A/F sniffer going to the KLX needle is a better way to go as it also allows you to lean out that main jet. Kawi had to over compensate due to lean MID throttle fueling dictated by EPA. Mild throttle...mid throttle
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Old 09-06-2012, 08:36 AM   #3828
Danger4u2
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Originally Posted by Aprilia View Post
.22 mod will certainly help with MID throttle surging but according to my A/F sniffer going to the KLX needle is a better way to go as it also allows you to lean out that main jet. Kawi had to over compensate due to lean MID throttle fueling dictated by EPA. Mild throttle...mid throttle
What year and model KLX needle and part # if you have it please?
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Old 09-06-2012, 09:14 AM   #3829
itsatdm
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The KLX adjustable needle is only used on the off road KLX 650r version. All years are the same. 1993-1996? Without a dyno or an AF sniffer, it is all trial and error. It will work for a KLR as the carbs are the same, but the jetting is different, a KLXr has 155mj. Air box mods and free flowing exhaust make a huge difference in jetting for your bike.

Every bike with a cap on the pilot setting is done to meet EPA emissions. They don't want you tampering with it. A consequence is the stock bikes are lean. The pilot controls the first 1/8 throttle, actually more than that. Get an extended screw to set it correctly while the bike is warm and running. screw it in and then out until it wants to stall. The correct setting is in between. Usually about 2 1/2 turns out.

The main jet augments the pilot. The needle controls where and how much it kicks in. The proper MJ can be determined under WOT. Too big and high rpm is soft. It you back off a bit and the bike accelerates it is too rich. It won't reach top speed if too lean.

After you have done that and it surges at steady state throttle, it is a needle height issue.

The air box and exhaust mods changes at what point the power comes on. I own a KLX 650c model. No adjustable needle. I did the washer mod while removing the the air box lid and added a free flowing exhaust. It killed the bottom end, but the bike was a rocket at high rpm. It also surged. Instead of fiddling with the fuel I added a baffle to the exhaust. I got my low end torque back, the bike was quieter and the surge went away.

For the 2 hp gained in all of these mods, a DJ kit is probably money well spent over the PIA testing to find the right set up.
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itsatdm screwed with this post 09-06-2012 at 09:51 AM
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Old 09-06-2012, 09:52 AM   #3830
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Originally Posted by Danger4u2 View Post
What year and model KLX needle and part # if you have it please?
itsatdm correctly stated...all years are the same. You need to purchase three items to make it work in the KLR carb. Several KLR specific websites offer it as a kit. One of which is from www.eaglemike.com specifically...http://eaglemike.com/KLX-jet-kit-KLXJK.htm
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Old 09-06-2012, 12:22 PM   #3831
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Originally Posted by ADW View Post
A surge at mild throttle settings at a steady speed sounds exactly like a lean pilot screw setting. The pilot screw has an aluminum plug over it from the factory, which is easily removed. You can then richen up the pilot screw and I'll betcha you'll find the surge has disappeared. http://www.klr650.marknet.us/carbairmixture.html
I might try that, I did it on a 250. I'm still not sure if it really "surges" or if it is the wind grabbing the front fender and hand guards. We get a lot of wind around here. After riding in different weather I will know. Overall it runs very well. I can easily live with it as is but I guess I wouldn't be attracted to this bike if I didn't like to tinker with it. The KLX adjustable needle seems like a good idea even if there is no problem. Does it allow you to adjust for altitude with a finger knob like I do on my old snowmobile?
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Old 09-06-2012, 12:41 PM   #3832
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Originally Posted by mcpenner View Post
Does it allow you to adjust for altitude with a finger knob like I do on my old snowmobile?
No. The KLX needle's height is adjustable while the carb is partially disassembled by means of a clip and a series of grooves along the needle's length. Choose desired needle height, insert clip in corresponding groove, and there you are.

A finger knob (or Kobuta T-handle) fuel screw allows adjustment of the idle air/fuel mixture. Useful, perhaps, at altitude, but--primarily only up to 1/8 throttle.

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Old 09-06-2012, 03:55 PM   #3833
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Originally Posted by XDragRacer View Post
No. The KLX needle's height is adjustable while the carb is partially disassembled by means of a clip and a series of grooves along the needle's length. Choose desired needle height, insert clip in corresponding groove, and there you are.

A finger knob (or Kobuta T-handle) fuel screw allows adjustment of the idle air/fuel mixture. Useful, perhaps, at altitude, but--primarily only up to 1/8 throttle.
My driveway is at 7400ft and I'm at less than 2Kft all the time. Stock CV carb works pretty well but yes, an adjustable fuel screw can do wonders for cold starting at altitude as well as throttle response. None of my FCR equipped bikes could ever cover that altitude range but then again the CV carb can never perform like a properly jetted FCR either. Thus why I'm working on FI for the KLR
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Old 09-06-2012, 09:02 PM   #3834
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I've read a couple posts on here about mpg on the KLR. I have an '03 with 19,770 miles and I'm getting about 33 mpg. Mostly hwy averaging about 70 mpg at 4500 rpm. Why is this so bad compared to what other people are getting? I run 91 in it. Thanks

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Old 09-06-2012, 09:24 PM   #3835
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Originally Posted by ahwarm View Post
I've read a couple posts on here about mpg on the KLR. I have an '03 with 19,770 miles and I'm getting about 33 mpg. Mostly hwy averaging about 70 mpg (I think you mean mpH) at 4500 rpm. Why is this so bad compared to what other people are getting? I run 91 in it. Thanks
Andy
Aggressive knobbies will lower MPG. I would start with checking the air filter, check the spark plug gap/install a new spark plug. With the bike running and an assistant watching lean the bike and watch to see if any gas dribbles out of the over flow tube. Could be the float is set wrong. Might be the valves need adjusting. KLR speedo's aren't the most accurate, check with a GPS.
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Old 09-06-2012, 11:58 PM   #3836
hoyks
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I get 5L/100km or near enough to 47miles/gal on my 08 running D606's. It has stock gearing, stock jets and 110km/h is the upper speed limit.

Only real mod I have done is to pull the snorkel and open out the exhaust a bit.


I too would give it a service, check the plug, re-shim the valves, screw in the main jet and then back it out the 2 1/2 turns and make sure the choke/enricher cable is lubed. If it isn't disengaging then you will be using more fuel than you should.

Has a previous owner messed with the jetting at all?
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Old 09-07-2012, 08:45 AM   #3837
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Quote:
Originally Posted by ahwarm View Post
I've read a couple posts on here about mpg on the KLR. I have an '03 with 19,770 miles and I'm getting about 33 mpg. Mostly hwy averaging about 70 mpg at 4500 rpm. Why is this so bad compared to what other people are getting? I run 91 in it. Thanks

Andy
What main jet is installed? Is it stock needle or aftermarket? Based on mileage I'd guess you have a 150 or 152 main jet. Stock main jet is too rich but needed with stock needle....
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Old 09-07-2012, 08:49 AM   #3838
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Not that I am aware of of. I pulled the air filter and plug this morning and they both looked good. I ended up replacing the plug just for good measure. I will have the valves done in the next couple of weeks.

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Old 09-07-2012, 08:51 AM   #3839
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Everything is stock.
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Old 09-07-2012, 12:38 PM   #3840
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Everything is stock.
Did you visually verify? I've had two bikes in the past two weeks in my shop who also swore theirs was completely stock. One had an adjustable fuel screw and both were rejetted by 'someone' who had no idea what they were doing other than bigger must be better.
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