Thread: The McCulloch 7-10 that is mine....

It's my first chainsaw, and I'm mostly new at small engines - I'm coming over from motorcycles and will be using the saw for 80% firewood, 10% trimming, 5% trail maintenance and 5% volunteer emergency work (if the need arises). I hope to use this thread as a diary for the life (and possibly retirement) of this saw, and so here's some background and my first question...

I picked up a McCulloch 7-10 from a friend. It didn't start well for him, and he didn't like it, it was old, vibe-y, smokey, and loud. So I got it. When it first found my hands, it didn't start for at least 30 pulls for a burp, and then another 15+ after that to actually get it running.

I spent the afternoon the next day pulling the thing and feathering the throttle until I got it running. When it buzzed to life, I found a happy medium with the throttle, just to keep it running. Took off the air filter and adjusted the idle after I had the engine warmed up (had to shut it off, since at first I didn't have a screwdriver long enough to do it. .....
After some trial and error, I found that turning the low-idle screw in raised the idle speed enough to keep it idling well, and I wouldn't have to feather the throttle to keep it going. Problem 1 solved.

Next I mixed some seafoam in the premix, and filled up the tank. Started it up, and ran a tank of that stuff through, just leaving the saw idling out back while preparing dinner. [Three cheers for bachelorhood.] Ran through the whole tank of gas, the saw ran it self out, and died. I filled up some more, and got it running again, tucked it away for the evening.
Next afternoon I was out again, and got it started and happily running again. I adjusted the idle again, this time raising it a bit more so it would stay running reliably when coming down off of the top-end full throttle. I took some trial cuts in a large log we had lying around - nothing through, just some starters. I let it idle some more, and noticed the clutch not always disengaging, so I lowered the idle a bit more, having found a screwdriver that fit the idle adjustment passage, I didn't take off the air filter this time. I filled another tank of the seafoam mix and put it away.

Friday I went out to take some firewood off a local's hands due to a recent storm. I experienced the first chain binding, and had forgotten tightening tools at home; so I took a load back and picked up those tools. Then I ran out of bar oil, and had also neglected that back at the house, so I returned with load two, and picked up the bar oil. All this time, I've been meaning to bring out the seafoam to just keep running a bit through each time, and every time I've forgotten.
One other point I haven't mentioned: my landlord has a Poulan that takes 20:1, and the McC takes 32:1 (according to the PO). So I add a dribble of two-stroke to the tank ever second fill-up, and that seems to keep it running happy. I plan to hit up Advance Auto Parts when I get my oil and filter for the car tomorrow, and grab a gallon tank while I'm there, this off-mixing crap is for the birds.... (Just so you have all the information in case you have a suggestion to make, once I get to my question/problem...)

We're almost full up for the third load, when the saw begins surging on idle, and then starts idling noticeably higher - higher enough that the clutch doesn't disengage, and the chain continues turning, albeit slowly. I realize this isn't safe - I didn't have the small idle adjustment screwdriver with me, so we planned to finish that load, and retrieve the screwdriver on the next trip home.
Instead, the saw had other ideas. (Is it normal to name your saw, like you'd name a motorcycle, or classic car?) Running high on idle, it would blub and die when given throttle. On a motorcycle I'd say drop the needle a notch in the carb, but I haven't done anything to the carb, and it was running well for the three hours before! True, this could be related to the high idling, and changing the idle mix might take care of it for me.... but as I've never dealt with this stuff before, I figured I'd ask the experts.

N.B.: I plan to premix some seafoam in the tank when I start using my own mixture, any reason I shouldn't?
Additional info: I did check the plug before, but not since the idling issue started. It was gummed up when I got the saw, but I cleaned the contacts and it's been okay since. Also, if it were a plug problem, I couldn't even start the saw at all, true?
I'm looking at pulling the starter cord mechanism apart, as it doesn't retract the cord all the way, until it stops - and then with a *Clang!* Words of advice, pictures, directions, .pdf's or other info for the rebuild?
Last thing: It leaks bar oil. I can tell, as I set it down when the bar oil tank is >1/2 full, and there's a puddle under it when I return. It's not the gas, that level hasn't changed, and it stops once the bar oil is below a certain level. Is this normal, or am I missing an O-ring os other seal somewhere?

Thanks in advance, and much appreciation to one member who has already been more than helpful with some specs and tips so far!
~Det

Det, a few ideas - 40+ years of chainsaws, I've never used 'seafoam', I don't even know what it is? A well tuned saw shouldn't need anything but the right 2-stroke mix in it. Buy a new plug [look up what one it's SUPPOSED to have, don't just replace whats in it. Many times it's a cure-all. If this saw's sat for years, it might need to have the carb rebuilt, as the diaphrams get old & dry. There's also a fine screen inside the carb, these plug up. Also, take the muffler off & clean inside it, carbon buildup can hurt too. The bar oil leak, you'll have to look for, find where it's seeping out. The pull cord/rewind could be built up sawdust & gunk in there & just need cleaning. One last thing, 2 strokes will carbon up faster than anything, especially if running a little rich. I'd never let one sit & idle through a tank of gas - never!

Det; I work on a lot of old chainsaws and sea foam is supposed to be a great cleaner for the fuel system but is not intended to be a cure all for a chainsaw that age. If I want to seriously run a vintage chainsaw and I do have around 50 to 60 of them and run at least 30 of them cutting wood,this is what I do to each and every one of them. First remove the muffler and inspect the piston , rings and cylinder through the exhaust port,check for scoring and carbon buildup,clean out all carbon deposits,dont damage any part surfaces,no metal tools.Clean out the muffler and reinstall with gaskets if all is good. Next clean out the gas and oil tanks with new gas ,swish and drain each a couple times then drain thoroughly.Check visually for dirt,crud varnish and corrosion and paint flaking,when all that is looked after install new fuel lines,pickup or filter in the gas tank. Next take the carb apart and do a thorough cleaning,remove the needle and seat if equipped,discard all gaskets , diaphrams and soak all metal parts in a container of carb cleaner. Take them out a couple hours later and clean them until they shine,blow all parts out really well with compressed air specially the small jets and passages,you can`t get a carb too clean. Remember the mixing screw passages also,blow them out really good.Now replace every thing with all new carb kit parts. An IPL works good here if you have not done a lot of carb rebuilds to get all the pieces in the correct order or make a note of all their parts and positions when disassembling the carb, setting the metering lever to its proper setting is critical as the carb will either flood orstarve if not set properly.
Reinstall the carb with new mating gaskets and hookup the new gas lines.Add mixed gas at around 40 to 1 mix ratio with modern two stroke for air cooled engines and start up your saw,if running with the bar and chain on add bar oil as well. Set the carb at around 1 turn out from lightly seated on both mixing screws and this gives you a starting point to set up the engine to run. With the T setting touching the throttle plate on the carb adjust to keep the saw running at idle. Then a small adjustment of the low speed screw in or out to get a smooth even idle just below clutch engagement should do. Next adjust the high speed screw to allow the engine to rev up to a reasonable high speed from idle, no more than 1 and 1/4 turn out or less than 3/4 turn in from lightly seated. I f the engine will not run well with these settings there is further correction work required.Sometimes a new plug of the correct type will help bring back better performance but not always,at least check to see if its the correct type,you never know what has been installed by the previous owner.
That would be another chapter and requires some detective work. Taking a 30 year old chainsaw out and working it without doing the above work will only result in a lot of frustration and lost time, don`t ask me how I know.LOL--LOL Pioneerguy600

Well I agree that a new plug, carb kit/rebuild and muffler cleaning are in order. also no more seafoam, just mix up some good two stroke oil at 32:1 (no more guessing) as a richer mix will smoke and speed carbon buildup. Before you do any of this do a leakdown test on the saw. The surging sounds like an air leak to me. You have a good saw there take your time making it right and good luck.

Originally Posted by pioneerguy600

Det; I work on a lot of old chainsaws and sea foam is supposed to be a great cleaner for the fuel system but is not intended to be a cure all for a chainsaw that age. If I want to seriously run a vintage chainsaw and I do have around 50 to 60 of them and run at least 30 of them cutting wood,this is what I do to each and every one of them. First remove the muffler and inspect the piston , rings and cylinder through the exhaust port,check for scoring and carbon buildup,clean out all carbon deposits,dont damage any part surfaces,no metal tools.Clean out the muffler and reinstall with gaskets if all is good. Next clean out the gas and oil tanks with new gas ,swish and drain each a couple times then drain thoroughly.Check visually for dirt,crud varnish and corrosion and paint flaking,when all that is looked after install new fuel lines,pickup or filter in the gas tank. Next take the carb apart and do a thorough cleaning,remove the needle and seat if equipped,discard all gaskets , diaphrams and soak all metal parts in a container of carb cleaner. Take them out a couple hours later and clean them until they shine,blow all parts out really well with compressed air specially the small jets and passages,you can`t get a carb too clean. Remember the mixing screw passages also,blow them out really good.Now replace every thing with all new carb kit parts. An IPL works good here if you have not done a lot of carb rebuilds to get all the pieces in the correct order or make a note of all their parts and positions when disassembling the carb, setting the metering lever to its proper setting is critical as the carb will either flood orstarve if not set properly.
Reinstall the carb with new mating gaskets and hookup the new gas lines.Add mixed gas at around 40 to 1 mix ratio with modern two stroke for air cooled engines and start up your saw,if running with the bar and chain on add bar oil as well. Set the carb at around 1 turn out from lightly seated on both mixing screws and this gives you a starting point to set up the engine to run. With the T setting touching the throttle plate on the carb adjust to keep the saw running at idle. Then a small adjustment of the low speed screw in or out to get a smooth even idle just below clutch engagement should do. Next adjust the high speed screw to allow the engine to rev up to a reasonable high speed from idle, no more than 1 and 1/4 turn out or less than 3/4 turn in from lightly seated. I f the engine will not run well with these settings there is further correction work required.Sometimes a new plug of the correct type will help bring back better performance but not always,at least check to see if its the correct type,you never know what has been installed by the previous owner.
That would be another chapter and requires some detective work. Taking a 30 year old chainsaw out and working it without doing the above work will only result in a lot of frustration and lost time, don`t ask me how I know.LOL--LOL Pioneerguy600

+1 on the 1 turn out this should be just about right assuming no lair leaks and a clean rebuilt carb, new fuel lines and no blockage in the muffler.

Yowzers, thanks for all the suggestions and advice everyone; I'll start with the plug, starter-pull, and muffler inspection.

I've done carb rebuilds on bikes before; they're not impossible but not my ideal of the best way to spend a day with an unfamiliar carb either. I'll leave that to phase two, since I'll also have to find a shop with carb rebuild kits around here, and I'm not sure where to do that. Should I check muffler gaskets too? There's some liquid (oil?) consistently showing up on the muffler during normal use...

I think I'll take off the bar and clean the bar oil lube area as well...
Thanks again!
~Det

Mix is too rich if there is more than a small sprinkling of liquid on the muffler. Also any lawnmower/ small engine shop should be able to get your carb kit. Do not worry about a carb rebuild taking all day. These carbs are pretty simple, even my first one only took 1 1/2 hour, now about 45 min. is all it takes. Don't sleep on the leakdown test, although it is not as likely to be the problem, if it IS then nothing else you do will make a difference. The carb on your saw is either a walbro or a tillotson and the carb rebuild kits are RK23HS for the tillotson and K10-SDC for the walbro. If you end up needing seals call Bobs lawnmower engine service in NY. at (607)-638-9297. Goods luck.

I don't have a 7-10 but I do have a 1-10, 54cc compared to the 70cc 7-10. This is a piston ported saw, so once you get the carburetor in shape there's not a lot more to it if the compression is good and the exhaust ports and muffler are clean. Ignition is pretty simple point/condensor stuff and I have not had any trouble getting a good spark on any of the McCullochs I have touched.

I am not sure how difficult it is to change out the seals on these models but I would suggest you strongly consider it as a leaking seal will cause all kinds of trouble and the parts cost too little to even think twice about it. On my older McCullochs, the flywheel side cover pulls off making changing the seals very easy. On my Jonsered 621 I just drilled a small hole in the seal and used a slide hammer with a sheet metal screw in the tip, worked real slick. From the drawings I have it appears the crank case splits right through the crank bearings which would make changing the seals easy enough if you can't get them out with a puller.

I have IPL's for the 7-10 which include the carburetors if you want to PM me with an e-mail address I can send them along.

Mark

Spent some time in Pa. about 20 years ago cutting with an old 7-10.Good saw.Tempermental as hell though.

Anybody know a good source for a set of rings for a SuperPro70?

First step is to try Bob's Lawnmower

Calvin (lawnmowertech37) says he has McCulloch parts

I have luck from time to time with Belgrade Sales, Belgrade MT (406) 388-1465 or ext. 6386

Mark

Thanks I'll give them a try in the morning.I'd like to get this one fired up.It has about 90lbs. compression.Cylinder is nice shape luckily.

Has good spark and it's getting fuel.Just can't get it to even pop.

Thanks for the reference Hoss, I'll keep the info on the kits, and the phone number's great too.

wow i love search engines guess what i need some advice guys on the 7-10 A clutch guard assy part # 88586 is that part a hard to locate part ?


yes i have one but it is new in the bag but must of been some pin hole in the package and the part has some that corrosion substance on it that white color substance that is on metals and stuff im wondering is there some type of chemical that stops this stuff from forming to much ?

any advice will be good

thanks
calvin

check fuel line also check if carb is sealed to the base?

Det, I recently resurected a 7-10A which has an automatic oiler. It too appeared to leak a considerable amount of oil. After two tanks of use, the issue has corrected itself and now the oil tank runs dry about the same time as the mix. I am not a carb guy so I was able to get a new Walbro SDC 58 for $62 including shipping. I was surprised that the h/l needles only needed to be about a turn out, as pointed out earlier. Now I've got a decent 70 cc saw with a 20" b/c that shakes the bark off of a hickory! Gotta love 38 year old chain saws.