CR80 Jetting

I am trying to make my wifes 1999 CR80 easier to ride in the bush.

I added a Moose Reed Spacer, Boysen Reeds, Steahly Flywheel weight, 14 tooth front sprocket. It already had a FMF Works Pipe and Shorty exhaust.

The bike now has a bog off idle only when the throttle is fully opened. If it is opened slowly to 1/2 then it runs fine.

I was thinking of dropping the main 1 or 2 sizes (currently it is stock at 125), but I have read that I may need to raise the pilot a couple of sizes to avoid a lean bog. Where is the pilot jet on the carb?

Also the bike has always "hung" when returning to idle. Kind of like a "pre-idle speed". When the throttle is released it slows to 1 speed then after 5 seconds goes down to idle speed. I have read that can be cured with a bigger pilot.

I have not done a chop test as of yet.

Also I replaced the head gasket a while ago as the bike was going through water. Someone mentioned that I may have "washed out" the cylinder/piston, therefore needing a new top end. Thoughts?

Am I on the right track? Any advice is appreciated.


ya my 02 cr80 was pretty much the same had a bog on the low end,i had a fmf fatty with shorty boysen reed pedals.i went down all the way to a 120 main and i think 2 sizes down on the pilot made the bog goaway but there was still no power on the bottom end,but tons on the top.the pilot jet is right be side the main jet u have to pull the float bowl off.

and mine idled just like your does i never did figure it out oh ya and i set my needle clip on the very bottom slot and mix the gas 50:1.wat do u mix ur gas at?

I am running it at 40:1, so far so good.

I bought 2 main jets, a 122 and a 120. I will try it out this weekend. I might try messing with the pilot as well.

I just bought a piston, ring and gasket set. If the jetting doesn't fix it up I will put a top end in it right away and see if that makes a difference.

Thanks for the input.


ya i had 122 ans the 120 didnt notice much differance between the two till a colder day then it was a bit lean with the 120.but i never could get any good low end power on it, i tryed new cylinder, pistion, ring help a bit in the top end.wat made the bigest differance way gearing, went down to a 14t the'll probaly find some more boton end power if u gear the front down a bit and the back up a couple:ride:

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