Jump to content
Sign in to follow this  

Jetting questions

Recommended Posts

Hey everyone,

 

I am headed to ride the trans american trail from Oklahoma to Moab in a couple of weeks. I have a Kehin carb  with a R&D flex jet fuel screw and am putting my stock exhaust on for this trip. I live at 600 ft elevation, but realize I am going to be hitting some pretty good elevation for this trip. Does anyone know what size jet I need to be running for best performance for this trip? Do I even need to mess with the jetting? I don't want it to be too lean for the oklahoma portion of this trip and do damage so I will probable switch jets when I get to colorado. Thanks for all of your help.

Share this post


Link to post
Share on other sites

We will be starting at around 700 and once we get to Colorado most of the riding will be under 10K ft with a few passes around 12K and 13K ft.

Share this post


Link to post
Share on other sites

It is actually on an SM, the guy i bought it from had switched it. I am not really sure what the current needle is. I will find out. Just thought maybe there was a formula I could use to factor what would work best.

Share this post


Link to post
Share on other sites

The more info you supply the better advice you will receive... :)

 

Which Keihin carb question has not been answered...If you don't know ,post a pic....also list any other know mods

Share this post


Link to post
Share on other sites

OK, it is a Keihin FCR carb. It has a 160 main jet. I have the stock exhaust on and the 3x3 mod done. I was told I should go down 2 sizes by a guy in Colorado. Would that be a 150 or 155? I can remember if there are 158 sizes or not. I am going to take a few different sizes with me just in case.

Share this post


Link to post
Share on other sites

OK, it is a Keihin FCR carb. It has a 160 main jet. I have the stock exhaust on and the 3x3 mod done. I was told I should go down 2 sizes by a guy in Colorado. Would that be a 150 or 155? I can remember if there are 158 sizes or not. I am going to take a few different sizes with me just in case.

 

It's going to be impossible to jet for that range of altitude....

Do you have the FCRMX or FCR Slant Body carb , which is the stock carb on an E model?

Is 3x3 mod done.?

Share this post


Link to post
Share on other sites

Here are pictures of the carb. Not sure which one it is, so hope someone can tell me. I realize that one Jet won't work for the whole trip, I was going to switch when I got to Colorado and reached higher elevation. It doesn't have to run great at the highest elevation. I am just looking for the best performance around 10k ft., which is where I will be doing a lot of the riding. I can change jets out at different points of the trip, just not sure how big of changes I should make.

photo 1-3.JPG

photo 2-3.JPG

photo 3.JPG

  • Like 1

Share this post


Link to post
Share on other sites

Here are pictures of the carb. Not sure which one it is, so hope someone can tell me. I realize that one Jet won't work for the whole trip, I was going to switch when I got to Colorado and reached higher elevation. It doesn't have to run great at the highest elevation. I am just looking for the best performance around 10k ft., which is where I will be doing a lot of the riding. I can change jets out at different points of the trip, just not sure how big of changes I should make.

Sorry, I have no idea why they came out sideways  :facepalm:

Share this post


Link to post
Share on other sites

Ok, It's Fcrmx......

 

The main jet and needle settings are what you will be needing to adjust if you want optimum performance during your trip..

You could get away with 1 jetting change of needle and main jet..

 

Presuming you have the 3x3 mod

 

To start off use

OCEMP needle, Clip 3 

155 main jet,

45 pilot jet

2 turns fuel screw

 

When you reach around 9,000 ft swap out to

OCEMR needle, clip 3 

140 main jet

the 45 pj should be ok, turn your fuel screw in to a achieve a smooth idle, 1.5 turns will be close

 

If it starts to run (stutter) rich before what I am calling "the scheduled" 9K jet change you could remove the air box side door as a temp fix or do the 9K jet change and partly tape the 3x3 opening.(cover intake by 30%).as you go higher , just remove the tape..

 

Have a nice trip... :)

Edited by Craig-o
  • Like 1

Share this post


Link to post
Share on other sites

Ok, It's Fcrmx......

 

The main jet and needle settings are what you will be needing to adjust if you want optimum performance during your trip..

You could get away with 1 jetting change of needle and main jet..

 

Presuming you have the 3x3 mod

 

To start off use

OCEMP needle, Clip 3 

155 main jet,

45 pilot jet

2 turns fuel screw

 

When you reach around 9,000 ft swap out to

OCEMR needle, clip 3 

140 main jet

the 45 pj should be ok, turn your fuel screw in to a achieve a smooth idle, 1.5 turns will be close

 

If it starts to run (stutter) rich before what I am calling "the scheduled" 9K jet change you could remove the air box side door as a temp fix or do the 9K jet change and partly tape the 3x3 opening.(cover intake by 30%).as you go higher , just remove the tape..

 

Have a nice trip... :)

 

Awesome!! Thank you so much. Thats exactly what I was looking for. I am wondering though if it would be possible to just change the main jet and leave the needle alone? I am not really familiar with carbs or there inner workings and would like to not open it up on the trail if I don't have too. I can just tilt it and take the nut out to change the main jet on the trail with little work. I realize it might not be perfect but would at least changing the main jet increase my performance?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...