KLX 140 carburetor swap

Wandell
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Wandell
I have a Kawasaki KLX 140 that I use as a pitbike. While riding last week my bike started cutting out. I thought I was about out of gas so I pulled in. I added some gas and it started pouring out the carburetor's overflow lines. Great! I guess my float is stuck so I need to pull the carb and check on that.

But this got me to thinking about going ahead and doing a carburetor swap. I know several members at Thumpertalk have reported good results by replacing the OEM 20mm Keihin with a 24mm Mikuni from a KX65. I was just wondering if anyone here had played around with a carburetor swap on one of these?? I see that this mod is also popular with Yamaha TTR 125 owners. I've been looking on EBay and there are a few used 24mm Mikuni's from KX65's and also a ton of cheap Chinese clones that are even cheaper than the used carbs. Does anyone have any experience with the Chinese clones? I know I had a Pitster Pro once that never had any carburetor problems (other than needing to have a richer pilot jet installed).
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seth505
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seth505 8/19/2019 2:05pm
8/19/2019 2:05pm
No experience with a clone but I didn't want to deal with possible issues so I got a mikuni vm26 for mine.
Wandell
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Wandell 8/20/2019 9:17am
8/20/2019 9:17am
Most people say the Mikuni 24mm makes a very noticeable improvement. How do you like your carb? Also, what did you do as far as the throttle cable?
Hondas4Life3
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Hondas4Life3 8/20/2019 11:56am
8/20/2019 11:56am
I swapped a ttr125 with a kx65 carb. You will need bigger carb clamps as the OEM ones didn't work. It was also a little tighter fit. Overall it made it run way better and with a few needle adjustments (clip position). Pretty sure I had to drill out the top of the cap for the throttle cable to fit? No bog, easy starting, and it definitely gained some HP. To get it perfect though you'll have to play with the jetting a bit.
seth505
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seth505 8/20/2019 3:01pm
8/20/2019 3:01pm
Wandell wrote:
Most people say the Mikuni 24mm makes a very noticeable improvement. How do you like your carb? Also, what did you do as far as the...
Most people say the Mikuni 24mm makes a very noticeable improvement. How do you like your carb? Also, what did you do as far as the throttle cable?
I had to make a custom connection on the airbox side and the throttle cable was actually a pain in the ass as well. I ended up using a throttle cable I found from a mini bike online parts store and still had to grind off some parts of the adjusters to get it to fit proper length/free play.

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pancake
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pancake 8/21/2019 12:45pm
8/21/2019 12:45pm Edited Date/Time 8/21/2019 12:48pm
I first swapped a VM26 on it, and that was an improvement. I'm currently running a Mikuni TM28 (vmr28) on mine and it's been a pain in the ass to jet. It's close, but I think I'm down to swapping needles and/or air jets.. Mikuni also makes a tmr28 that has an accelerator pump that might be worth exploring.

I'm currently running a cone filter on the tm28 but I do plan on modifying the stock air box so I can tie into it vs pulling hot air from around the exhaust.

I got the tm28 from engines only.. but it had a 15 pilot and 210 main in it. The 15 is okay, but the 210 was a million times too rich. I'm at 8500' in Colorado so I've backed the main down to a 135 and it's as crisp as it's ever been.. light years ahead of the stock carb.
socalxr
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socalxr 8/23/2019 9:45pm
8/23/2019 9:45pm
I'm using a Keihin PWK28 with a 170cc kit with a cam and pipe. Pain to jet. Ended up using a pod filter, 100 main, clip in the middle, 40 pilot, 1 1/4 on the airscrew.
Wandell
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Wandell 8/25/2019 6:57pm
8/25/2019 6:57pm
I ordered a used KX65 Mikuni and it has arrived. I'm just waiting on some jets I ordered and a 40 degree elbow for the throttle cable. Jury is out on whether or not I'll need it or not. Is the length of the KLX throttle cable the issue? It sure has a funky attachment to the stock Keihin carb.
Wandell
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Wandell 8/27/2019 8:31pm
8/27/2019 8:31pm
My jets arrived so I installed them and cleaned the carb. I found a piece of 1.5” outer diameter pvc at the local hardware store and used it to extend the boot going to the air box. I decided to go ahead and mount the kx65 carb on the bike until the throttle elbow from Sudco arrived. Everything went smoothly so I decided to attempt to Jerry rig the throttle cable and start the klx. The piece from the oem Keihin elbow and a 1/4 inch drive socket eliminated enough slack from the cable that I was able to adjust it enough to get the throttle to work. I mounted the fuel tank, connected the gas line and double checked everything while I turned the fuel on. The klx fired up as soon as I touched the starter! I had to adjust the idle but it ran smoothly on the stand. So of course I decided to bolt the seat on and take a test drive as the bike warmed up. I could definitely tell the bike pulled harder throughout the rev range! Now I’m just waiting on the Mikuni throttle elbow to arrive so I can connect my throttle correctly. Hopefully I won’t have to get a different cable or throttle. Thanks to everyone for the information you shared about swapping carbs!
Wandell
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Wandell 9/2/2019 4:02pm
9/2/2019 4:02pm
My 40 degree Sudco  throttle cable elbow for the Mikuni  finally arrived (even though I ordered it from an Ebay vender in the next state, they took forever to ship it). I bolted the Sudco elbow onto the Mikuni carb's cap. I was able to mount the OEM  KLX140 Keihin's throttle cable fitting onto the Sudco elbow and route the OEM  KLX throttle cable through it and attach it to the Mikuni slide and adjust the throttle cable with no problem. Actually, I was worried the OEM KLX140 throttle cable was going to be too long but I got it adjusted fine. In hindsight, a 90 degree elbow may have been better but the 40 degree version worked. An elbow that would swivel when mounted to the carburetor cap would have definitely been better. I finally got to do an extended test ride today and so far I really like it. I did a couple of 15 minute motos on my backyard pitbike track and the bike ran great! The jetting is really close but I'm probably gonna open up the airbox a little more. Definitely an improvement over the OEM carburetor!

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