I have an 07 kawasasku brute force 750. It has about 600 miles on it. It spits and sputters and sometimes backfires at low speeds and sometimes at an idle. It runs good at higher speeds. The carburetors have to been cleaned and new fuel were put in. I have been told it eithers needs a valve job done or it needs a new cdi box. Was wondering if someone could give me an idea on what to try?

 

It will be a good idea to check/adjust the valve clearance if you've never done on the 750. But trying a new CDI will be a big waste of $$.

If the problem existed from the beginning, you need to check to make sure you have the correct sized needle jets (2) in the carbs.

If the problem developed over time, you need to RE-CLEAN the slow jets in the carbs, and/or check the free movement of the needle jets and vacuum slide.

 

had the same exact issues on my 05 & 06 750i brutes- both had under 600 miles on them.
after me cleaning out the carbs multiple times, flushing the fuel tank out and replaceing the plugs & plug leads- I took it to the dealer and they changed the jets- fixed the (that) problem.

 

Yep.

Those tiny pesky jets are hard to clean properly. If you try to use a thin wire, you may succeed sometimes but can also accidentally elarge it and make engine running too rich at low speeds. Got to be careful. They are cheap enough to just replace if you don't feel competent.