Need some serious help on a finicky Mac 10-10

[Gaspowered]

Hey there, This is my first post on this forum. So about a month ago a friend of mine brought over his late father's McCulloch 10-10 automatic for me to get running. It's one of the older models with no chain brake. It was bought in 1971. He said that he wanted to see it run again, and it had been about 35 years since it last ran. When I got it, it had no spark, the tank was bone-dry and very clean,and has excellent compression. I cleaned and re-gapped the points at .020", and installed a new Champion DJ8J plug and gapped it at .025". I took the carburetor apart it was pretty clean inside, with a bit of varnish, so I blew out the ports with Gumout and compressed air. (The carb is a Walbro/McCulloch SDC) I rebuilt it with an oem carb kit, set the metering lever height with the Walbro tool, and installed a new fuel line and filter. I put in fresh 32:1 mix and it did start, but immediately died. I had both needles set at 1 1/2 turns. Still died. I took the muffler off and cleaned out the carbon build-up. Still starts then immediately dies. I even pushed in the metering diaphragm with a small screwdriver a bit to "prime" it. It coughed and spit out raw fuel from the muffler. I managed to flood it once, and pulled the plug and dried it, and after that, nothing. Any suggestions? I am not going to give up on this saw.

 

[heimannm]

Make sure the coil to flywheel clearance is set to 0.010" and try another spark plug...even new spark plugs can be faulty. I would also go through the carburetor again as there may be a small bit of varnish plugging one of the ports. Take the H and L screws out and make sure the passageways are open and passing carburetor cleaner when you squirt it. Also check the fuel filter as it may have been plugged with varnish.

You will get a lot more attention to your questions if you post this in The unofficial Mac 10-10 thread in the chainsaw stickies section or the McCulloch Chain Saws thread.

Mark

 

[Gaspowered]

Make sure the coil to flywheel clearance is set to 0.010" and try another spark plug...even new spark plugs can be faulty. I would also go through the carburetor again as there may be a small bit of varnish plugging one of the ports. Take the H and L screws out and make sure the passageways are open and passing carburetor cleaner when you squirt it. Also check the fuel filter as it may have been plugged with varnish.

You will get a lot more attention to your questions if you post this in The unofficial Mac 10-10 thread in the chainsaw stickies section or the McCulloch Chain Saws thread.

Mark

Thanks for the reply. I am new to these forums, I will try to post my question at the McCulloch thread. It has nice blue spark, but I will try the coil clearance anyway. I tried another plug earlier, with the same results. I am going to take the carb apart again and remove the larger welch plug, I removed the smaller one earlier and replace the screen. I replaced the fuel filter and line so that couldn't be it. Thanks for the help though.

 

[svk]

Just for S and G, pour the gas out into a clean container. Is it still clean? I’ve had a couple Macs where the paint inside the tank was flaking and raised havoc with the carb.

 

[Gaspowered]

Just for S and G, pour the gas out into a clean container. Is it still clean? I’ve had a couple Macs where the paint inside the tank was flaking and raised havoc with the carb.

I will work on the saw tomorrow, and this morning I refilled the tank. I will check it tomorrow, but I'm sure after about an hour of (trying) to start it it wouldn't have blocked it. Can't hurt to check the filter again though. Never thought about that paint. I hate it when some companies painted their carburetors and tanks. Something's deemed to get crapped up!

 

[svk]

I’ve had a few different brands of saws do that and the small flakes get past the filter and gum up in the carb. Had a generator with rust in the tank do the very same thing. I did the Red-Kote treatment to that one though.

 

[Gaspowered]

I’ve had a few different brands of saws do that and the small flakes get past the filter and gum up in the carb. Had a generator with rust in the tank do the very same thing. I did the Red-Kote treatment to that one though.

I did replace the fuel line, and the old one had the filter that was just a cork-shaped block of foam that slid into the "sleeve" at the end of the line. The new eBay fuel line I got was meant to work with a "clunk" style filter that you see in newer saws. I used one of those Walbro felt ones with the band around them that you see in Echo, Tanaka and other Japanese equipment. I have taken those apart before and they actually have a little screen inside similar to the carburetor filter screens. Maybe that could be clogged?

 

[svk]

Sure could be. It’s hard to guess till you check everything.

 

[Gaspowered]

Sure could be. It’s hard to guess till you check everything.

Yeah. I've never had this much trouble with a McCulloch saw before. Hell, I got an old Mac 130 Minimac for free and the gas in the tank turned brown and smelled like the septic tank of an RV, I flushed it out, fresh gas, started right up!

 

[alexcagle]

Verify your impulse passage isn't clogged up.

 

[Gaspowered]

Verify your impulse passage isn't clogged up.

Could be a possibilty. Next thing I was going to try is take the insulator block off and check if any gasket material or crap is clogging the passage. No pulse, no fuel... makes sense. Thanks, I will definitely check it tomorrow.

 

[Conquistador3]

For what's worth try a different carburetor if you have one at hand or put a few of drops of premix directly in the intake port and see if the saw gives any sign of life.
Sometimes carburetors need more than a good bath and a new set of gaskets to get back in shape or they are just beyond salvation. I've had a couple of Walbro's many years ago driving me literally nuts and the only fix was replacing them. Post-mortem found what was wrong in one but the other is still "dead for causes unknown-possible voodoo". These days I just keep a batch of carburetors around for particularly hard cases: they really do help.

 

[Gaspowered]

For what's worth try a different carburetor if you have one at hand or put a few of drops of premix directly in the intake port and see if the saw gives any sign of life.
Sometimes carburetors need more than a good bath and a new set of gaskets to get back in shape or they are just beyond salvation. I've had a couple of Walbro's many years ago driving me literally nuts and the only fix was replacing them. Post-mortem found what was wrong in one but the other is still "dead for causes unknown-possible voodoo". These days I just keep a batch of carburetors around for particularly hard cases: they really do help.

That would definitely be a good solution, and I do have another SDC carb laying around but the larger welch plug is smashed in, and it's a different model with no idle speed adjustment but i'll try to remove the damaged plug and see if it's still worthy. I'm pretty sure it's the carburetor because my main problem is that it will start, but immediately dies. Every time I clean points and get spark, I always dump some two-stroke gas in the cylinder. I usually don't give up on carburetors, but hey, you can't win em all! I got a box full of random carbs so I do have misc. parts. I'll just have to dig through it.

 

[Conquistador3]

Best of luck to you. Walbro SDC carburetors are only available as NOS and very occasional used unit at obscene prices.

 

[MacAttack]

For what's worth try a different carburetor if you have one at hand or put a few of drops of premix directly in the intake port and see if the saw gives any sign of life.
Sometimes carburetors need more than a good bath and a new set of gaskets to get back in shape or they are just beyond salvation. I've had a couple of Walbro's many years ago driving me literally nuts and the only fix was replacing them. Post-mortem found what was wrong in one but the other is still "dead for causes unknown-possible voodoo". These days I just keep a batch of carburetors around for particularly hard cases: they really do help.

I had one Zama carburetor from a Husqvarna leaf blower that i just gave up. I took it completely apart, could manually get carb cleaner through all passages, replaced internal parts, but that SOB would not prime. The primer bulb would create a vacuum on the carb and pressure on the tank but gas would NOT fill the fuel line. I finally had enough and replaced the POS which is now sitting in my drawer of carb parts.

 

[Gaspowered]

Best of luck to you. Walbro SDC carburetors are only available as NOS and very occasional used unit at obscene prices.

Well, update on this thing, I took the carb back off, removed the larger welch plug, and blew it out with Gumout and compressed air like there's no tomorrow. I also tried another fuel pump diaphragm. Put it back on the saw, and of course, it started then died. At this point i'm tempted to rule out the carburetor. It's got great blue spark and probably round 100 psi of compression. I also hooked up a temporary fuel line to act like a "tank." I could see the fuel getting drawed in, but only within 5 pulls. I even took out the plug and blew out the crankcase to get rid of excess gas. I checked the impulse line; it was clear. Only other thing I could think of is maybe a bad crank seal?

 

[Gaspowered]

I had one Zama carburetor from a Husqvarna leaf blower that i just gave up. I took it completely apart, could manually get carb cleaner through all passages, replaced internal parts, but that SOB would not prime. The primer bulb would create a vacuum on the carb and pressure on the tank but gas would NOT fill the fuel line. I finally had enough and replaced the POS which is now sitting in my drawer of carb parts.

What type of primer bulb was it? Remote or mounted on the carb? Sometimes on those on-carb primers the little duck bill valve can go bad. On the remove tanks, I try to memorize the fuel line routes. Long barb-Tank Short barb- Carburetor. I once had a Craftsman leaf blower that had a Zama carb that wouldn't prime, I figured out the fuel pump diaphragm gasket had some material clogging the little hole where the bottom of the duckbill valve is. Simple little things like that but they're so hard to spot.

 

[MacAttack]

What is your spark plug telling you? If the saw dies and the plug is wet with gas, it's likely not the carb. Then look to spark issues, and you said the saw had no spark when you got it.

But... starting then dying, is usually not getting fuel. Will it run a few seconds if you pour gas into the sparkplug hole?

 

[Gaspowered]

What is your spark plug telling you? If the saw dies and the plug is wet with gas, it's likely not the carb. Then look to spark issues, and you said the saw had no spark when you got it.

But... starting then dying, is usually not getting fuel. Will it run a few seconds if you pour gas into the sparkplug hole?

Spark is fine. I think I figured it out. I swapped carbs earlier with the one off of my 6-10 and it ran for a little bit. From another thread, apparently it's supposed to have a check valve in the main jet. I didn't see one when I took it apart, it probably turned into mush.

 

[Gaspowered]

Yep, I think that's it. Unfortunately I replaced the welch plug so i'll have to get another one. Maybe someone was in there before me, i'll never know. Strange considering that it looked like it have never been touched and it just wasn't in there.