Jetting advice: rebuilt xr600

Hi, sorry for the topic, I know everyone hates giving jetting settings cold. Anyways, I'm halfway thru my XR600s engine rebuild, and completely forgot about jetting. I have a hotcams stage 1, intake porting and am putting in an Arias 10.5:1 compression piston, and had the head rebuilt (valves cut or replaces, seats cut) on stock bore. Previously I had a 172 main in there and it was just about right on. I know I'll have to go up, and I will buy a spread of jets. However, do you all have an idea where I should start from and go to?

Thank you!

Elevation? What mods did you have before the rebuild? What pilot jet?

If you didn't have all of those hop-ups before the rebuild, then I'm surprised it wanted a 172 main. That would be too much for my bike even at sea level.

Depending on what pilot you have, I would leave the jetting alone and see how the plug starts coloring. A way to monitor oil temp is a good idea too.

Sorry, it had the hotcam stage 1, full exhaust and intake porting before the rebuild. Plug color was perfect and it felt great with no hesitation from 1/2 throttle on. I'm at sealevel. I'm just wondering the range.

Then the only thing being added to that combination is the piston, right? If that's the case, then the jetting probably won't need to be changed unless pinging on 91 is a problem. The higher compression ratio can also pull a stronger signal on the jets and slightly richen the mixture that way.

Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now