OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters McCulloch Trimmers & Brushcutters McCulloch 2816 snipper

Hi
I believe I have a carby problem with this old machine and would like to get a kit to see if I can get it going.
It's a Zama and the number appears to be M29D 71Q?
Anywhere I can get a repair kit and how much?
Thank you

I believe that carburetor would be a Zama C1U M29D. Is your McCulloch trimmer by any chance called a Model 2816 Roadrunner? Not that it matters, the C1U M29D seems to be a well-known carburetor and a kit should be easy to get.

Thanks for the info. Yes it is a 2816 machine.
There seems to be so many kits in the parts section online I am unsure which one to order?.
Also, I noticed that who ever had the machine before tightened the the long adjusting screw down so far that it is also damaged. Do you know if they also available in the parts online?.
Many thanks for you help/

In case you don't have it Pedro, here is the Zama Tech Guide:
http://www.zamacarb.com/pdfs/TechGuide_2007.pdf

The overhaul kit for the c1u m29d seems to be called RB-48 (all of the Zama overhaul kits have part numbers beginning with RB). It seems the kit does not include mixture needles, however:
http://www.sears.com/zama-carburetor-rebuild-overhaul-kit-zama-rb-48./p-SPM506253514P

I suggest you send a Private Message to Bruce, the Outdoorking site owner. He will probably be able to tell you whether the mixture needles are available, and from whom.

Grumpy.
Bruce commented that if the adjusting needles have been screwed down tightly then the seat would be damaged and I would need to get another carby. I understand that but where do I start to look for another carby?. Anyone suggest somewhere?. I have googled but nothing on replacement carby only repair kits.
Thanks in advance.

Partstree apparently has the C1U M29D to sell, but for $120 plus shipping I think a decent second-hand whipper snipper would cost considerably less.

The problem caused by over-tightened needles is that tuning becomes excessively sensitive - tiny adjustments cause major effects on air/fuel ratio. I can tell you what I would do in your situation, as a desperate alternative to throwing away the snipper - whether you do it, and whether you are happy with the results if you do, are matters for you, not for me.

First, I would grip the head of the mixture screw in the chuck of a bench drill, and spin it up. Then I would gently polish the taper at the needle end of the screw with some abrasive paper of at least 400 grit, with the aim of removing the graunch marks while retaining a straight line of taper at the original angle.

This is a rather unlovely procedure, but it will probably make the mixture screw at least work better than it does now. If the result was unsatisfactory, I would look around for a second-hand carburetor that will mount on the same studs and gasket as the Zama. The carburetor would preferably not be another Zama: a Walbro would be favourite.

Thanks for your advice and assistance. Yes I guess you're right about paying $120 for another carb. However, I will try your suggestion about polishing the taper, it's worth a try that's for sure. If that doesn't help, it's probably tip time for it. Appreciate your time and advise in helping with my problems. Best regards Peter

Just one point when you are doing the polishing, Pedro. Between the mashing of the needle and the polishing it back into shape, the usual step up at the big end of the taper (marked in red) may come closer to the mixture needle's seat in the carburetor body:



That step must always be far enough back to have no influence on the needle setting, so you may have to move it back toward the screw-head by half a millimetre.

A report on how you go with this operation would be very useful to other members.

Grumpy, after having a close look at this needle, it seems beyond repair to me. What do you think?. Pedro cimg0960.jpg[/img]

Pedro, the image identification string was truncated somehow when you used the image posting facility. There isn't enough left there for me to recover it by editing. Could you post it again please?

[img]https://www.outdoorking-forum.com.au/forum/uploads/usergals/2013/03/full-1463-10061-cimg0960.jpg[/img]

I'm not sure what has gone wrong with your post, but when I post the same string myself it seems to work.

Unless the tip of the needle has been broken off, I can't see anything wrong with it Pedro. The tapered bit seems straight and smooth. What does the needle tip look like when viewed along the needle's axis?

Hi I have resent the image again but it isn't showing up on my Mac? I logged in on a PC and the pic was there? Please let me know if you haven't got it and I will try again. Sorry for the errors and hassles. Peter

No problem, I don't know what is going wrong but I just re-posted the same string on this PC and the image appeared in my post. What I'm hoping to find out is whether the tip of the needle has been broken off, or it is just supposed to have a large blunt tip. A picture of the tip taken axially instead of transversely may give us the answer. If the tip has broken off, the needle is a goner, it would be difficult to machine a whole needle tip onto it unless you have a jeweller's lathe and are quite a bit less clumsy than I am.

Grumpy, I thought that the needle was "sharp" and not blunt as it is in the pic?. With little knowledge of what an original is like, I really can't comment on it. If you say it appears OK then maybe I'll get a repair kit and try it out. Thanks again for your guidance. Pedro

The needle's tip might be supposed to be either a full cone (sharp point) or a truncated cone (blunt tip). Without seeing a known good one or being familiar with the carburetor, I can't tell except by inspecting the tip of the needle to see its surface finish: does it look machined, or broken? Because the tip looks square to the axis of the needle, I thought it might have been made that way in the factory.

Grumpy, Had a look under mag scope and it appears to me that it could be original shape. What do you think if pic is clear enough. [img]https://www.outdoorking-forum.com.au/forum/uploads/usergals/2013/03/full-1463-10062-cimg0961.jpg[/img]

I can't tell if that is a fracture surface or a machined surface, Pedro. Can you focus on the tip instead of on the shoulder?

Grumpy, it's the best I can get with a point and shoot cam using auto focus and macro. I'll try to get a better shot if I can. I seems to me to be OK coz there doesn't appear to be any raised metal towards to outer perimeter, which I assume would be evident if it was tightned down hard.? Pedro

Let's go back to square 1: what makes you think this carburetor has a problem? What are you trying to fix?

Acquired second hand. Told the machine was difficult to start. Pulled down and cleaned piston, no spark, replaced plug which was completely fouled up, oil residue everywhere, still no spark, found replacement coil, now have spark. Pulled carby off to clean, as mentioned, oil dryed throughout carby, diaphragm needs replacement, maybe petrol plunger also. Decided to get repair carby kit. Have not yet received kit and after checking adjustment needles, concerned that the carby may be shot anyway. Best can hope for now is to install carby kit and see if it fires up. If it doesn't, guess it may be time to retire the lot?. Pedro

If there is a fair amount of soft black carbon in the combustion chamber and exhaust port, the previous tenant may have been using too much oil in the fuel, and/or letting the engine idle a lot. However before letting it go at that, I suggest that you check the compression with and without a small (tea)spoonful of oil put into the combustion chamber through the spark plug hole. If the compression increases substantially with the oil in place, chances are the piston rings are worn out or damaged. Also, take a look at the crankshaft seal to see if it is leaking (The 2816 appears to be a cantilevered crankshaft design, with only one seal).

If one or both of the diaphragms are stiff and/or have wear marks, the carburetor needs an overhaul kit. So far I see no reason to suspect a problem with the mixture needles, which really only happens if the previous tenant has played with them.

Essentially, most whipper snippers are disposed of because they have become difficult to start. Sometimes the reason is that the spark plug has deteriorated or dirty fuel has blocked a fuel filter (in tank or carburetor) or less often, a jet or passage. In the remaining cases, either an incompetent tenant has messed them up (and there are usually visible signs of this) or a possibly competent tenant knows very well that they are worn out. You go through a process to find out which of these three failure modes has occurred.