# zama c1u m29d main nozzle question



## wa5ngp (Aug 14, 2010)

I have been working on a ryobi string trimmer with a c1u M29D 7za it seems like forever. I've given up finally but at this point I'm just curious.

I cleaned the carb several times but it always was difficult to start and after starting would not stay running. I finally concluded that the
problem was in the main nozzle check valve. I concluded this after noticing that when I primed and while running it lots of air bubbles were in the fuel line on the way back to the tank. If I bypassed the carb the bulb worked fine (no air) so it 
was getting air somewhere in the carb. Reading the pdf from zama on the c1u carb they mention the main nozzle only a little and
say only work on it if you are sure that's the problem. They are not very clear on how to remove it or put it back. They did mention that the check valve is important for proper fuel delivery.

The final straw was when I removed the choke shaft a small ball hopped out no where to be found. At this point the work was just for my education so I drilled out the brass plug pressed into the body since I could not press it out from the throat side or pry it out. The net is that brass plug just got destroyed and the carb body with it but I never found where the main nozzle check valve was. It would appear that if you think the main nozzle check valve is the problem its time for a whole new carb as its just not obvious from the zama directions or from studying the thing how its possible to get that thing out to clean it to make the check valve work. 

What am I missing?

Don


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## glenjudy (Aug 26, 2006)

I'm guessing the little ball that popped out when you removed the choke shaft was a little friction ball to keep choke in whatever position you placed it.

The ZAMA tech_guide clearly shows main nozzle and it's check valve in the illustrations.
Ostensibly, the main nozzle and it's check valve, on a lot of the models, can be forcibly pushed out towards the carb throat, and a new one pressed in.
Also, many of the ZAMA carbs have idle check valves, but they can't be replaced.
If you spray wd-40 thru the H port, you will see spray come out main nozzle in the throat.
How did you clean the carb ??
If you soaked it in a dip for a long time, and/or, blew it out with blasts of high pressure air, it's quite possible you damaged the check valves.

There are gentler ways to clean these little carbs.
HTH


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## wa5ngp (Aug 14, 2010)

*main nozzle*

You are correct about that choke detent ball. When that happened I kinda punted.

I sprayed carb cleaner in there a lot and pushed a wire (big no-no, I know better but I had become desperate) thru the hole in that brass plug. That's probably what ruined it. Like you say I may have broken the small valve inside there if its brittle. I had thought that all the areas that have fuel flowing them were easily removable and could be cleaned but I guess not in the case of main nozzle check valve. What is the best way to clean that valve, spray carb cleaner thru the needle port and hope for the best? It does not appear that the carb kits include that valve. Looks like trying to remove it may damage it and or the body and its not easy to put back.

I saw some wording about not soaking the whole thing. What is the reasoning for not doing that? Does it ruin the gaskets? I didn't do that.

I did learn to keep carb cleaner away from the primer bulb as it seems the cleaner makes them get hard and crack.

This trimmer was an old throway thing that was given to me that I hoped I could make work and if not learn something in the process so I'm not too annoyed. There may have been some work done on it before me that made it hopeless. Always more to learn.

thanks
Don


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