KX 265 jetting

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Sep 10, 2003
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#1
Howdy all, Having trouble jetting my KX265. Thought I was on the right track but not so sure now. Fires right up and runs well with the choke on but as soon as the choke is off and the throttle rolled on it bogs and dies. I thought it was a too lean pilot circuit and have gone to a 60 pilot jet but same problem here to. Am I still too lean? seems like a 60 should be getting close - any suggestions? gotta run the dog to the vet, back soon.

Rob
 
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Dec 8, 2003
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#2
I did 265 to my bike this year, I am very good at jetting and my bike is always jetted properly. After installing 265 I had to lean the needle 1 step other than that the rest of the jetting was good. I would assume your bike would'nt change drastictcally either. Sounds like your way off somewhere else. Check carb, power valve, and for air leaks.
 

Senior KX Rider

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#3
I agree with Ron. Your jetting shouldn't need that much change. I would look for an air leak. If you put a non oem(paper) base gasket on it I would be suspicious of a leak there. I had a similar problem when I first put the cylinder on my 310. Pulled the cylinder and replaced the base gasket with oem and the bike ran like a top. As I worked the cylinder on I bent the paper gasket and had and it did not seal right.
 
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#4
Senior KX Rider said:
I agree with Ron. Your jetting shouldn't need that much change. I would look for an air leak. If you put a non oem(paper) base gasket on it I would be suspicious of a leak there. I had a similar problem when I first put the cylinder on my 310. Pulled the cylinder and replaced the base gasket with oem and the bike ran like a top. As I worked the cylinder on I bent the paper gasket and had and it did not seal right.
Used the Cometics set that Eric sent along, torqued to the right spec, nothing really apparent going on as far as a leak goes but I will search further. Thanks for the feedback guys!
 

Eric Gorr

Engine Builder
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#5
Thats a big pilot. I think that the pilot circuit is clogged. Sometimes air filter oil can run down the airboot and collect in the bottom of the air bell on the back of the carb. Thats where the air feed for the pilot jet is located. I think you should clean the carb by removing the pilot jet and air screw, then blow air through the passage to flush it out. Thats about the only thing that can make the engine die when taking it off choke.
 
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#6
Thanks Eric, Did that a second time yesterday afternoon, backtracked to a 52 pilot (had a 48 in it pre-work) airscrew out 1 1/4, needle in the first clip position, 158 main. Got it up an runnin, rode it a bit and the throttle response was good so we'll see how it does today, I've got a 50 pilot in standby
 

MXTex

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#7
I've got the jetting on my 98 KX265 dialed. Excellent throttle response. Excellent plug read. No spooge. Porting is mo-better-everywhere. Premix is Motorex @ 32:1. Reeds are Boyeson pro-series, pipe is stock, fuel is pump gas (93 octane). Keep in mind, this is in Houston, TX right now (70 to 80 degrees F). Mid-summer could require leaner jetting. Generally, the 2mm over kit drove leaner jetting for me.

Main 155
pilot 45 (stock)
clip 2nd
a.s. 2

Good luck.