Zama carb rebuild?

[dgallow]

Took the Zama C1S-S1A carb off the 011 for a rebuild using the Zama RB-11 kit. The only difference in parts is the new diphragm pump is made of smooth mylar?? vs the traditional material on the old diaphragm pump. Anyway, I pressure tested the carb and it would not hold pressure. Immersed it in water and the air leak is around the perimeter of the pump cover, gasket and diaphragm. Do I need some type of sealant for the mylar diaphragm?

This carb took an inordinate amount of time to prime when gas tank was refilled. That was my reasoning for the rebulid. Other than that the saw runs just fine!

 

[Fish]

It is a common problem with the Zamas, and Stihl's response is,it needs a new carb.
But if you have a customer with a trimmer that is one month out of warranty, it is a hard sell.
I fixed it with a careful light coat of indian head gasket shellac on
both sides of the diaphram, worked, but would make the next rebuild a mini-nightmare........

One reason that I hate Zamas

 

[dgallow]

Went by the dealer today and got that same response, "Carb housing or body is warped and carb needs replacement ($60). Any of the diaphragm materials will work."

Well not according to the Zama site FAQ.

How do you know whether to use the mylar or rubber diaphragm in a kit?Answer - If the surface of the carburetor is smooth use the mylar(clear or shiny black material), not smooth use the rubber diaphragm.

I found an RB-11 replacement kit with both diaphragms. Carburetor Repair Kit Replaces: Zama RB-11

Eventually I'd like to have a Walbro carb for this saw.

 

[dgallow]

Lightly smoothed the surface on carb side of housing with fine emery and reinstalled the old diaphragm. A few small tooling marks remain on the carb housing and are likely preventing a perfect seal (didn't leak test again). Leak is very slight at this point (say 40 min to lose 7" of pressure) and the saw tunes and runs well.

Still having a problem of the fuel line not holding prime when the saw cools down. I can make it prime faster by removing air filter and occluding intake with my thumb while pulling starter rope. Presume the grub screw in tank vent could be at fault? Or the small leak in carb is enough to lose prime? Or both?

Your Thoughts?

 

[Fish]

Likely the leaky carb.