2006 Rmz 450 Pulsing idle with back fire issues.

So i just recently purchased a rmz 450 it has a white bros exhaust and k&n filter on it. When i got it it has some back fire but i didn't think it was that bad because he had said its been sitting for a while and needed a carb clean. i Just figure the pilot jet was somewhat clogged. Took it home and have been working on it, i completely cleaned out the carb and it was still back firing. I noticed the pilot jet was at 42 and the main at 170 so i bumped up to the pilot to a 50. i was thinking this is way to much but i figure since it had an exhaust and filter it would need it. Well the back fire is basically almost gone but still comes in barely at high idle. But now this bike is running SUPER hot like so hot it started melting my radiator guard down by the header and it really started to get me worried. Could it be something else? Ive heard sometime a lean mixture with make the header hot. Do you guys think maybe i need to go up another pilot jet? It is idling a lot better not with the new pilot jet but still has a little bit of a pulsing idle it will go up and down frequently. Not quite sure what could be doing this either. Ones i put it in first it runs great I'm just having the problem with idle and the extreme heat off the header. Any help would be great thanks. 

What year RMZ? What's your elevation?


Did you retune the fuel screw for the 50 pilot?


Did you try tuning the fuel screw with the 42?


When you cleaned the carb, did that include removing the fuel screw and cleaning that passage and checking the condition of its oring and verifying the screws tip wasn't damaged or broken?


Check for air leaks around the front and rear carb boots.


Check for exhaust leaks around header.

45 pilot

Ream the passage above the pilot jet with solvent and fishing line (90 degree bend)

Replace the fuel screw oring (air leak)

Replace the slide plate seal

Service the hot start (corrosion, air leak)

reads like a lean condition,,, possibly an air leak...

So its a 2006. Im at 4500 ft elevation. 


Before i put in the 50 i replaced the fuel screw completely with a new oil ring and spring, i got one with a knob cause i was tired of trying  to jet it with just the stock.

i have tried adjusting on both the 42 and the 50 now.


I havent noticed any leaks but i will double check for any. I'm thinking maybe i didn't get the carb on straight or something now. 


So i did clean all holes really well but i did notice my hot start was looking kinda funny I'm not sure what a good and corroded looks like I've never had a bike with a hot start this is my first. Could this also be causing a lean mixture if its not working properly? 


Thanks for the replies 

So i went around reading and turns out my hot start was stuck and causing it to run super lean. I cleaned it and put it back together and it seems to be doing a ton better. Especially with heat. I still get a pop every now and then but i think i may have a leak on my exhaust also. Im going to repack my exhaust and check my headed. It seems to just be popping now on the deceleration so I'm guessing thats what it is.

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