McCulloch super pro 81 giving me trouble, fixed!!

[LumberJack1940]

Recently purchased this saw from Jon, one of the best guys I've dealt with by far.
so here is the Problem. got it in the mail (packed great) cleaned the styrofoam off and put some gas it in it, pulled it few times and its running good. set the lo and idle screw (non adj. sdc, would like a 65sdc with upturned screws). later that night it wouldn't start at all just pop off no matter where the lo was. rebuilt the carb with a new k10 kit. only put in the parts that looked like the ones that came out. started finally after that and ran great, next day go to my buddy's house and went to start it and it would only pop after every two pulls after choke, got started and would die after a few seconds, getting plenty spark, lot of compression, but fuel coming out the exhaust as mentioned in the advertisement but will still pop over. took it home and slapped an all adjustable sdc off another mac and it ran and idled great. then the same problem started happening the next day or when I shut it off. metering lever is set to spec level with the two bosses on the carb. any help will be appreciated, It's a fine saw and I want to get it running like a top again

Thank you
-Jack

 

[LumberJack1940]

Bueler? anyone?

 

[sawfun]

Could it be a tank vent issue?

 

[LumberJack1940]

I really don't think it is the vent in the fuel cap

 

[rwoods]

Just for fun swap the cap off your 10-10 or 55 and try again. Ron

 

[watsonr]

Make sure the high and low needles are not rounded on the ends allowing free flowing fuel. Set the metering lever just under level, you can adjust the high or low to feed it more.

 

[Four Paws]

How are the tanks designed on these? Could a gasket be compromised and leaking fuel in the case?

 

[watsonr]

no. Tank has two pieces and the top is mainly a cover. The carb box is just basically a flat floor sandwiched between the carb and cylinder.

 

[LumberJack1940]

It has a fixed high jet sdc do only the low is adjustable. I have the metering set spec right now but will try again. The same things happened when I put another sdc off another Mac

 

[watsonr]

Was the saw warm? The vent is in the tank, but those saws, being the tank sits on top of the cylinder, gets pretty hot. The vent is under that small metal disk in the cap. Pry that disk out, bet you find a small rubber vent turned to goo and not working properly. The fuel gets hot, builds pressure in the tank and then just pumps the cylinder full of fuel. Try running a bottle to the fuel line, that would eliminate the pressurized tank from the equation and if it has no issues running off a bottle, I'd go after the vent.

 

[LumberJack1940]

been off the grid for a few days sorry guys.
if it sits overnight I can start it the next morning with choke, push choke in and it starts normally but it dies seconds after and will only pop every other pull, will try two different caps. I have my 10-10 cap, 55 cap, and don't homelite caps fit? also I put a new fuel line in. thanks for the replies everyone can't wait to get it running tip top, the only other thing it needs is new mounting hardware for the dawg

 

[LumberJack1940]

took the muffler cover off this morning (haven't been home for a few days) and there was fuel sitting in the muffler back by the outlet and it had to be at least a few oz of fuel or moreas when I poured it out of the muffler a good amount came out. used three different caps didn't help, adjusted the metering lever just below flush didn't help, bottle fed didn't help. just want to have a good running big mac and not the regret of buying it
Thank you
-Jack

 

[watsonr]

check the high and low needles, are they rounded or pointed? Check the inlet needle as well. Is the metering diaphragm holding the inlet needle open?
attached is the SDC manual, maybe something in there you missed. Metering diaphragm and gasket in the right order and holding it open?

 

[turtle561]

ignition-clean &set points,air gap. sounds like problems i had with a 028. after putting in new condenser with no change, it was obvious it was the coil. with a new coil it was fine.

 

[Four Paws]

Take the carb off the saw. Then inspect.

Damn regret.

 

[LumberJack1940]

Will tear the carbs apart again for inspection. Currently have the cover off for ignition inspection. Sad to find out a part of te start is cracked a good ways. Thanks for the replies, hope to have it going and not have a boat anchor or wall hanger lol pulled money from my savings for this Mac

 

[Four Paws]

If you have fuel puddling without the carb, then you can eliminate the carb as the problem. If not, focus on the carb. I would listen to Randy (watsonr) as he has some good experience on these vintage machines. Should be a reasonably simple fix, then you'll be enjoying 5 cubes of vintage power at a good price.

 

[LumberJack1940]

cleaned the points, set at .018, every mount for ignition system isn't corroded and doesn't need to be cleaned but it seems to be getting intermittent spark. put my makita impact on the flywheel and turned it over and would get spark normally but then it would cut out and then after being spun for seconds longer be back and then quit again. if it's ignition I can throw my pro mac 55 ignition parts on to check right?
Thanks a bunch guys!

 

[LumberJack1940]

switched coils, got it set and gapped and finally got a good consistent spark and it fired great and when i shut it off it wouldn't start again, no spark again. I have an atom ignition chip off the pro mac 55 I can try on it as well

 

[Four Paws]

Check your kill switch for continuity. I have had old switches fail and remain 'off' when in the 'on' position.