carb comparison question

I have an 04 atv carb and a 07 dirt bike carb.

why does the 04 have some type of pilot diaphragm and the 07 doesn't?

Is the 04 supposed to have a hot start plunger? It just has a cap with nothing in the hot start hole.

Its running lean and i found a missing o ring in the diaphragm and no hot start plunger in the hole. I'm thinking its def the problem.

Yes, there's supposed to be a hot start plunger, and if it's missing, you'll have a huge air leak.

The pilot diaphragm is the same as that on a WR450 carb. It's part of the air cut valve, which is an element of the air injection system.

Yes, there's supposed to be a hot start plunger, and if it's missing, you'll have a huge air leak.

The pilot diaphragm is the same as that on a WR450 carb. It's part of the air cut valve, which is an element of the air injection system.

I figured you would know if anyone would. Does the air valve need to be on the carb or can it be removed and blocked off?

It can be, but there is some compensation that must be made for its absence, and I'm not clear on the details. In a YZ450, air is fed to the pilot circuit through a single jet and passage. In a WR/YFZ, the air passage is forked, with one side bringing air in through a pilot air jet, and the other through the ACV. When the ACV is blocked off, the PAJ needs to be larger. See the WR450 forum for more info.

OK thanks gray, Apparently you can flip the diaphragm and block the passage then add a larger paj or maybe smaller PJ.

I know the standard yz passage pulls from the paj, do you know where the second passage draws its air from?

I could trace it if I had a carb in my hands, but no, I don't.

ok, thanks gray.. It looks like it might go up into the top of the carb above the slide...

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