Jump to content

XR650L Jetting

Recommended Posts

I put on a new, Big Gun exhaust pipe, it was back firing and poping pretty good, I pulled the carb to see what size main jet is in there, to my surprise I had a 142 main jet. In my manual it calls out for a 150 main at or above 6500 ft. Do you think i will need to change the pilot jet? Does this sound right?

Edited by dlee

Share this post


Link to post
Share on other sites

Anyone??? I guess if I don't hear from anyone I will start with 155 main, 52 pilot, at 5500 feet, I guess I will do Dave's mods as well

Share this post


Link to post
Share on other sites

One reason you might not get instant answers on this is because we seem to answer this one about three times a week.  Have you looked through other discussions on jetting for the past month or two?

You might be on the rich side with a 155, but that's what I would put in there if it were me.  Mine runs great up to 6000 feet with a 158.  But with a high compression piston the jetting needs to be a bit richer.  If your bike seems a bit rich when you go up to higher altitudes, then you can switch to a 152.

Share this post


Link to post
Share on other sites
4 hours ago, ScottRNelson said:

One reason you might not get instant answers on this is because we seem to answer this one about three times a week.  Have you looked through other discussions on jetting for the past month or two?

You might be on the rich side with a 155, but that's what I would put in there if it were me.  Mine runs great up to 6000 feet with a 158.  But with a high compression piston the jetting needs to be a bit richer.  If your bike seems a bit rich when you go up to higher altitudes, then you can switch to a 152.

Jetting DOES NOT need to be richer with higher compression. Increasing compression will make a motor run richer with no other changes.

Share this post


Link to post
Share on other sites
53 minutes ago, JoeRC51 said:

Jetting DOES NOT need to be richer with higher compression. Increasing compression will make a motor run richer with no other changes.

I do it to help reduce the chances of it overheating and from having detonation issues.  Otherwise it would probably be slightly better with a 155 in there and I'm sure it would get closer to 50 mpg rather than the 40-45 it gets now.

Share this post


Link to post
Share on other sites
1 minute ago, JoeRC51 said:

I've always gotten around 36 MPG since new.

The mileage on mine went up with the high compression piston.  I was in the 30s before that too.  Other than being a bit tougher on the starter motor, I don't see any other downsides to higher compression, but I have more power everywhere. 

  • Like 1

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:


×