Zama C1U – K27A gasket question

[bgsengine]

Hi Andy

According to the Zama manual, if the flat surface of the pump side of the carburetor had been machined, use the mylar diaphragm. If the surface has been left as cast, use the soft flexible diaphragm. All the best,

Sky

Hmm... I do not believe I have ever seen one that is *not* machined flat - to a very fine R.A. (almost mirror polished) Interesting.. don't recall reading that in the Zama manual..

[KE4AVB]

BGS, That is actual in the service tips pdf and I have seen a couple that weren't machined; don't remember which ones as they were on some really old stuff when I was self teaching myself how to repair these cubes.

http://www.zamacarb.com/page/service-tips

[KE4AVB]

Sky thanks for getting me to look up the reference material related to your post as I was needing the pop off test pressure. I thought it was around 5 psi and it is 10 psi instead.

[andytw]

Hi, thanks for all of the further updates.

The carb is back on the cultivator, it started fine and the 'L' and 'H' adjust OK.
Net result is that it idles fines and revs up cleanly and drops back to idle, so all looks good.
Just wondering if you can tell me where the check valve sits in the scheme of things.
The reason I ask is that when I press the primer, it ejects fuel back into the tank via a clear pipe.
But when I release the primer it sounds to be drawing air together with fuel from the tank.
Consequently what I see in the clear 'return' pipe is fuel and air.

Apart from that it runs fine.

andytw

[KE4AVB]

This is normal; although, a leaky main nozzle or welch plug can make it excessive. What happening air is being drawn in pass the mixture screws through the ports in the venturi. I have seen few leaky main nozzles but those carburetors would not even pull fuel in from the tank because of this. I had a C1Q on a Stihl last month that would not prime. What I found was the welch plug over the main nozzle was completely missing allowing too air much to drawn in from the mixture ports as it bypass the mixture screws. Had to replace the whole carburetor because someone had already had the carburetor apart and lost the old welch plug.

If your engine runs fine then there is nothing to worry about.