400 EXC Rust in my carb... Why? How? Now what?

[mrmodine]

Hey Guys:

I was doing some jetting tonight putting in the new EMN needle and I got to looking around.  I was wondering what was inside the piece on the bottom of the carb next to the float plug which is held on with 3 allan screws. 

I was a bit surprised when the part that came out was covered in rust.  Now, I have no idea what this part does but rust can't be good.  It is a small metal piece (round) which appears to slide into a larger round rubber bushing.

Why the rust?  Can I just clean it off with contact cleaner and put it back or do I need to replace it and/or go digging for more?

Pictures can be seen with these links:
http://home.earthlink.net/~csmithktm/images/carbpart1.JPG

http://home.earthlink.net/~csmithktm/images/carbpart2.JPG

Thanks for any help you can provide...

 

[mrmodine]

Picture

 

[enmerdeur]

this is the pumping diaphram that gives you a squirt of fuel when you first open the throttle. This was the same on my YZF. What happens is when you wash the bike water gets down in there and rusts it. Mine never did stop functioning but after seeing it for the first time I was careful not to hose that part down too heavily. I suppose you could pull back the boot after washing and give it a shot of compressed air or something.

 

[Jim G]

Once in a while I would have to clean build-up off of the actuator arm for the diaphram.

 

[MWEISSEN]

Newer FCR carbs are built not to have this sealing problem. My '99 WR used to get crud on the open side of the diaphram too (but not that bad!). Pull out and clean up the accelerator plunger rod, and put a light amount of waterproof grease on it. I also packed the rubber seal at the top of the actuator with grease.