[Wayne195]

I'm trying to get a mcculloch mac 110 running for a friend of mine. After he adjusted the carb it wouldn't run anymore. It does have spark. I have gotten it to run for a few seconds on starting fluid, but it doesn't continue running at all. It would seem like the carb isn't drawing fuel in.

Anything else I could try?

 

[mla2ofus]

Screw both mixture screws in 'til lightly seated, then back each out 1 to 1 1/4 turns. If it will start then try to fine tune the mixture screws while it's running.
Mike

 

[Wayne195]

Screw both mixture screws in 'til lightly seated, then back each out 1 to 1 1/4 turns. If it will start then try to fine tune the mixture screws while it's running.
Mike

That's exactly what I did, but it still won't run.

 

[mla2ofus]

I'll suggest taking one mixture screw all the way out and cranking it over to see if gas is being pumped.
Mike

 

[hairyapple]

If it's got a park and some compression the only thing left is the carb. It doesn't take much to clog them up.

 

[Roanoker494]

First, never use starting fluid on a 2 stroke engine. The only lubrication these engines get is from the oil mixed in the fuel and the starting fluid strips all that oil away, it only takes a few seconds without oil to trash a piston. Just pulling the engine over without oil will cause damage, even if the engine does not start.

The Mini macs do have a couple weak places in the fuel system. Check the fuel line first, bet it needs replaced, and I would go ahead and rebuild the carb while I was there, these saws are a pain to take apart and there is no use in having to do it twice. If you are lucky your 110 has the Walbro MDC carb because kits are readily available and cheap. If your 110 has a Zama m1m7 you are going to have some trouble because those kits and no longer available from Zama, there are no known aftermarket kits and when NOS kits show up they usually sale for $20+ dollars.

Carb kit for the MDC is
Walbro D1mdc
Stens 615-435

The fuel line is regular 3/32 x 3/16, or you can use 1/8 x 3/16, fuel line available from many dealers and some auto parts stores.

 

[WNYTractorTinkerer]

So it was running BEFORE he adjusted the carb??:dunno:

Hard to evaluate the thing from his say-so unless he's a service person but I doubt that because he passed it on to you.. (BTW- starting fluid in a 2 cycle should be used very sparingly- no oil in it!)

Another possibility is a busted or leaking fuel line as mentioned above.. That saw is aged a bit so evaluate it's integrity..

Here's a thread that has been kicking around for some insight as to what to try:
http://www.mytractorforum.com/showthread.php?t=223371

 

[Wayne195]

So it was running BEFORE he adjusted the carb??:dunno:

Yes, it was running. the reason he tried to adjust it was because he it was idling a little rough and he thought he could improve it by adjusting the carb.

Thanks everyone for your input; unfortanently I didn't get time to look into this further the last few days, but I will try and get it figured out this weekend for sure.

 

[Wayne195]

OK, the carb on this one is the Walbro MDC.

I'm going to order a repair kit off of Amazon and hopefully it will run now.

 

[Wayne195]

Hmm, I did find some $5 diaphram/gasket kits for my carb, but the actual repair kit is a little more expensive.

I'll need more the complete carb repair kit...correct?

 

[wa5ngp]

If I were you I'd just take the carb appart and see how things look inside. Clean it out with brake fluid spray not carb cleaner (too agressive). Keep the cleaner away from plastic parts like the bulb as it will disolve and crack. Remove carb screws (if you can) and shoot the cleaner thru there.

My guess is that the problem is related to gasahol. I've fixed a few weed eaters with a similar problem. Lately when I finish sawing I dump out the fuel into my riding mower and run the saw until empty.

Next time I start over with a fresh mix. Even with stabil the fuel is only good for about 1 month especially if its exposed to a lot of air. So I only mix 1 quart at a time with fuel less than 1 week old. I think weed eaters are more subject to the problem since the engines are smaller and the fuel ports in the carb are so tiny.
don

 

[wayne50]

When spraying out the passages and any holes in the carb. with carb. spray did not fix the problem on small engine carbs, I have had good luck lately with just taking the carb. off and soaking it in gasoline for a day or two, then blowing it out with compressed air.

 

[WNYTractorTinkerer]

Makes me wonder if your bddy cranked the needles down & distorted the jets.. I usually put a bit of fuel in the carb with an eye dropper to verify the problem IS fuel related. If it fires that is the trouble.. I'll wager a bet he messed with the jets due to it not running right..


You verified the jets are ok

Other causes to think about:

Dirty fuel
busted fuel pick-up line
plugged fuel filter
Pull the muffler to evaluate the piston/cyclinder

Just some thoughts to ponder..

 

[wa5ngp]

Yeah, I forgot about muffler clog up. It hasn't happened to me but I've heard of the problem.

I had one carb that would just NEVER idle. I finally tried pushing a fine wire thru there (a no-no) but no luck. Soaked it in everything. Finally I gave up on it. If those inside passages get clogged it tough. Only other thing I would have liked to have tried was an ultrasonic cleaner. I ended up replacing the whole carb.

To insure that it is the carb I usually just fill some fuel mix into a hypodermic needle and spray down the throat. If it fires for a while you've got a big clue.

don

 

[Wayne195]

Well here I am again and the McCulloch still doesn't run. I have completely rebuilt the carborator, but with no success. It does fire when I spray starting fluid into the carb (not a recommended procedure). but it is still quite obvious that it is not pulling the fuel into the carb. If I'm not mistaken, the fuel is supposed to be pulled into the carb by the vacuum of the piston. Do any of you have a clue what else could be the

 

[wa5ngp]

My money would be on the carb. Something didn't work right in your rebuild. Were you able to remove the mixture screws and spray carb cleaner thru those ports? Like I said in one of my rants, this gasohol is gumming up lots of good 2 cycle things. I rebuilt a ryobi weed eater Zama carb lately. Around the fuel level channel in the carb base there was a substance that looked like RTV sealer that I had to scrape off with a small screw driver as even carb cleaner didn't take it off.

You've got spark and I think that you are getting enough vacuum. Instead of starting fluid just take a syringe or eye dropper and spray a bit of fuel mix into the carb throat. I bet it will run for a bit. I doubt that you have hurt anything yet but actual fuel mix will eliminate that possiblilty.

I assume that you when you depress your fuel bulb that fuel is coming thru the lines. Also be sure you have the fuel lines reconnected properly. The bulb pulls fuel thru the carb back into the tank. Its very easy to get them mixed up.

My 31 cc Mcculuch has been ultra reliable. But then, I always run it out of fuel and mix up a new batch the next time. I don't even know what kind of carb is in there and hope to keep it that way.

Don

 

[Grand Sierra]

If its never been a runner, whats the compression anything less than 115 you may be wasting your time and money! Intake ,compression, power, exhaust. Start with compression first on any engine, step one compression tester.