ATJ_Number_1 Jetting

I just bought a BST40 from a KTM. To do the ATJ_Number_1 mod. I was wondering if any one could give me an idea of were to start on the jetting? I ride between 4500 ft and 10,000ft elevation. Im not very familiar with jetting.

Also if there is anything else that could help me with the carb, I would be greatly appreciated.


I know you already bought the bst40 but the bsr42 needs no mods and jetting has been tested quite a bit by some of us here on tt with good results.

Thanks for the reply. I looked for a 42mm on ebay I didn't see any. So I went a head and bought the 40mm for a good price. Luckily I work at a machine shop the machinist are going to help me get the mods I need.

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