Zama carb clogged?

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  #1  
Old 09-28-09, 03:07 AM
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Zama carb clogged?

Hi.
I've got McCulloch 835AV chainsaw with zama carb M28D.
I've changed all those membranes and rubbers, needles, not long ago. I bought that carb rebuild kit and it worked fine until two days ago.

It suddenly started to choke itself when you press accelerator. On idle, it worked fine for a while and only choked when you pressed accelerator, then after a while it started accelerating on itself when on idle, and then decelarating, and accelerating again until it choked in idle too.

So I tried few usual steps among which was pumping the gas with small thumb pump. But it was blocked, you couldn't press it.

So I thought it's one of the tubes which is bent or clogged and I checked all of the tubes, but they are fine.

Looks like the carb is clogged, so I disassembled it, cleaned everything, removed fuel (there was decent amount of it inside) and used one of the tubes to hook it on the carb extensions (these 2):
Imageshack - fotografija0012

and blew with my mouth to see if passages are clean. They were. So I put the carb and chainsaw together again and tried it, but it still had the same sypmtom. You can only press the pump twice until it's blocked, so you can't pump any fuel in the carb.

What else can I do with it, which holes to blow into and how? Is there something else to try? Those are other pictures of the carb and its holes so if you could point me what to blow into or what to do:
http://img18.imageshack.us/img18/248...afija0007k.jpg
Imageshack - fotografija0008p
Imageshack - fotografija0009

I can't take this chainsaw to the service as it is just too expensive, but I need it.

Could this malfunction have happend because I've leaned my chainsaw when sawing trees (not very big trees actually, few inches of diameter max)?
I'm asking this because the guy who serviced it before said that it's meant to work in upright position only (it's saw vertical to the ground), just to cut wood shorter, because it's a 'toy' chainsaw.
 
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  #2  
Old 09-28-09, 06:32 AM
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Your carburetor is a model C1Q M28D.

Note: Refer to Parts List for Ref. No.

The problem you were having can normally be corrected by adjusting the carburetor. Attempt to adjust the carburetor without removing the limiter caps Ref. No. 53 and 54.
If the carburetor will not adjust you may have to remove the limiter caps Ref. No. 53 and 54. These can be pulled off with pliers.

Nothing you did caused this problem. Chainsaws are designed to cut in any position.

How to adjust typical diaphragm carburetors:
USA Zama : Service Tips

C1Q Parts List:
http://www.rottmansales.com/IPLs/zama/C1Q.pdf

Zama Technical Guide:
http://www.zamacarb.com/pdfs/TechGuide_2007.pdf

Product Look-Up. Everything on one page.
USA Zama : ZAMA Products
 
  #3  
Old 09-28-09, 07:32 AM
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thank you airman.

I don't think there is a store near me which has those parts on stock.

I'd like to diagnose my problem correctly because otherwise I could get stuck without parts to replace, as it seems that once you remove those limiters, you must replace them.

It says that I should remove welch plug and do something underneath it if carb gets clogged.

I just tried to pump fuel in unmounted carb and the fuel can enter metering chamber, but can't get through to the diaphragm chamber (no matter how hard you press the primer pump), so if you could say which channels are clogged, as I don't understand how they are connected together and I'm having trouble understanding it from manual as well. I just need to know whether it's necessary to remove welch plug and/or limiters or not. And is it necessary to remove welch plug first, to be able to remove limiters or not?

The needle, lever and spring system is ok, also, the hole under the needle which leads to the diaphragm chamber(throttle) is clean and ok.
 
  #4  
Old 09-28-09, 08:23 AM
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If the inlet needle valve (Ref. No. 20) is sticking, fuel will not flow to diaphragm chamber (pump). Check for sticking inlet needle valve by gently pushing metering lever (Ref. No. 22). Polish sides of inlet needle valve and hole it sits in with metal polish to prevent sticking.

If you remove the limiters, you do not have to replace them.

Do not remove the welch plug.

Refer to Parts List for Ref. No.
http://www.rottmansales.com/IPLs/zama/C1Q.pdf


If I help you fix this, I want Cevapcici and a Miš Maš for payment.
 
  #5  
Old 09-28-09, 09:55 AM
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thanks again!

inlet needle isn't sticking, it's moving up and down as you press or unpress the lever.

can you please explain how to remove those white and red limiters for Hi and Lo rpm adjusting.
 
  #6  
Old 09-29-09, 07:00 AM
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Is this how you would remove those limiter caps from the carb?
drop.io rzntfwb
If yes, it's really hard to pull them out, I can't do it without maybe applying too much force for them to survive as they bend and squeek when I pull them, but won't get out.
 
  #7  
Old 09-29-09, 07:30 AM
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I sent you a Private Message (PM) - read it.


Originally Posted by vbr666 View Post
Is this how you would remove those limiter caps from the carb?
drop.io rzntfwb
If yes, it's really hard to pull them out, I can't do it without maybe applying too much force for them to survive as they bend and squeek when I pull them, but won't get out.
 
  #8  
Old 09-30-09, 11:55 AM
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hello again,
just wanted to let you know I fixed the carb.
just did as you told me.
removed those limiter caps (white and red), unscrewed both screws and used small hose to blow both holes with my mouth.
that fixed the problem.

thank you very much again!
 
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