Gotta jet question.

12 replies to this topic
  • Evilfirbolg

Posted February 26, 2005 - 05:16 PM


Picked up some Keihin jets from the dealer and am about to tear open my carb but upon looking at the jets I have and looking at pics on the web and in my exploded carb pic I notice that my main jet is quite a bit longer than the one that appears to be in there(1/2" compared to what appears to 1/4" in the pics). Do I have the wrong jet? Or do I just put that big ole sucker in the needle jet holder and go for it? It's a 160 if that matters. Thanks.

  • LaneMM

Posted February 26, 2005 - 08:38 PM


Its possible you have the wrong jet. Dealers dont always know everything. However, the pictures arent always exact representations. Unless you cant be without the bike, take the old jets out and take em to the dealer to match em up.

  • smashinz2002

Posted February 26, 2005 - 09:26 PM


The main jet should be about 1/2" long. Keihen main jet. The picture is not correct because none of the jets are 1/4" in length.
whoa!! Wait a second here, I just noticed you're from Texas? where in Texas? I ask because a 160 main jet, if your bike is properly uncorked, is too small! Here's a guide (bike uncorked of course):
1. elev. sea level: 180 main jet. B3E needle at third position (middle), or stock needle at 4th from the top. (airbox should be drilled, use high octane fuel)
2. up to 1000' elev: 175 main jet, same needle settings.
3. 1000 to 2000': 165 to 170 main, " " "
4. 2k to 3k' : 160-165 main, ditto needle
5. above 5k' : 155-160 main. ditto again
These are just suggestions, depending on riding style it could vary. Airbox should be drilled, 40mm intake boot is a must, won't work otherwise. Use stock headers, stock silencer, use 40mm HRC exhaust tip, preferably cut off the internal spark arrestor screen/baffle cap. Run highest octane possible, preferably avgas 100LL.
All of this will give maximum power with the engine being stock, meaning no hot cam, bore job, or high comp. piston.
Have fun with it, this bike is very tunable for different situations, you can use a stock, but drilled exhaust tip (34 or 36mm, spark screen remains), with a slightly leaner main jet to get smoother power and quieter tone, and less noise. Low end torque will suffer, but I use this setup for riding in Colorado, so not to attract attention with excessive noise.
'00 XR650R
'04 KX500

  • Evilfirbolg

Posted February 26, 2005 - 11:27 PM


Great info smashin sir, but I should have mentioned, this is an XR650L not an R. Dunno if that makes a difference but sounds like it does. I have a K&N filter, stock headers, Big Gun Race can, and will do the snorkel removal, slide drill trick. 55/160 seemed the combo that stood out. Am I wrong? Do I still have the right jets? I have a 58/165 combo as well and can get whatever.
Thanks again.

  • Hayden

Posted February 27, 2005 - 07:57 AM


Did you read this?


Im working on a 94 L right now. I got the 55/160 in there with full WB exhaust and K&N. Did everything the site above suggested. I havent run it yet as I am waiting for the rear shock to get rebuilt. This is going to be my Moab bike this next month. From what I have read the 55/160 is a good starting place. With the full pipe, I may have to go up to the 165 or 167. Although the Alt. in Moab is higher than here in KS. so I may be alright. The Main Jet where the Needle sets should be spot on and same diameter and physical size as the one you take out. Now the pilot is the one that is recessed some and it is a longer jet. My stock one was a 50s which means a short. You can get a long one and cut the top off to match the s size. I had a problem finding a 55s so just bought the 55 that they had and cut it down. From the threads down the two jets were the same. The 55 just had a longer barrel if you will from the treads up. So I just made a s out of the longer 55 pilot to match the one I took out. I would say your on the right track with jet sizes. Run the 55/160 and go up from there.


94 L

  • Hayden

Posted February 27, 2005 - 08:06 AM


I just reread that link and it seems that one guy was running a 55 long jet from BDesigns. I guess it doesnt make any difference wether its a Short or Long Pilot Jet. Hummmmm???


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  • Evilfirbolg

Posted February 27, 2005 - 08:43 AM


Yessir, I have read Dave's mods and know them by heart. I've also read about 20 other versions and feel confident and ready to do the job. Seems if you use the long pilot you just need to trim a bit of the plastic slosh widget. My question is the jet in the holder, arrow point ing to it in this pic...

Posted Image

The jet I have looks like the one here circled in red, the jet in Dave's pics looks like the one here circled in green. My question is will the one I have(the lady in red) work or do I need to go back and get the lady in green?

Posted Image

Thanks again for ya'lls patience with my newbie self.

  • jws

Posted February 27, 2005 - 09:43 AM


just so were all on the same page - do you have a "R" or a "L" ??????????????

  • Evilfirbolg

Posted February 27, 2005 - 10:23 AM


As stated above I have a 2005 XR650L . Just from my perusing I am guessing I was given jets to an R . But in my neophyteness am unsure and wish to confirm before I proceed to tear my bike apart and discover what I have will not work.

  • jws

Posted February 27, 2005 - 12:09 PM


As stated above I have a 2005 XR650L . Just from my perusing I am guessing I was given jets to an R . But in my neophyteness am unsure and wish to confirm before I proceed to tear my bike apart and discover what I have will not work.

yeah thats what i thought - i missed your second post but figured you had a L - the pic of the main jet circled in red is for an R i know that for sure - i dont know to much about the L :)

check out the yahoo group

  • Hayden

Posted February 27, 2005 - 07:54 PM


Yep the one circled in green is the jet for the L model. The R jet wont work.


  • Evilfirbolg

Posted February 27, 2005 - 08:24 PM


Thank you so much Sir Hayden, you have saved me a major pain. I will remedy the situation tomorrow. Thanks again.

  • Hayden

Posted February 28, 2005 - 06:54 AM


Hummmmm ..... Sir Hayden......I like the sound of that :)

Sir Hayden

94 L

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