McCulloch Chain Saws

[heimannm]

Check for spark...if itis really an 81E it should have the two piece electronic ignition and there is a problem, the later one piece ignitions are readily available and will bolt right on.

As long as the cylinder is in good condition, everything else can be found if needed.

Mark

 

[JSMississippi]

How slow?

Cannot really see the needle moving. I'd say it dropped roughly 1psi/min, maybe a bit less. I'll measure the rate tonight if it is make or break. I can for sure hear the leak at the seal, especially if I wiggle the crank, although I do not see any difference in the needle moving on the gauge when I do so.

That seal can be changed in place....carefully and patiently. But it can be done.

Some may disagree but at this point I would break her in half to replace the seal, check the bearing and inspect everything while I had it apart. like @vinnywv said the PTO seal can be replaced without disassembly but they are more difficult than the flywheel side seal.

The danger with trying to replace the PTO side seal without separating the crankcase halves is damaging the bore where the seal sets. Trying to pry the old seal out and getting a new one back in can be done but I find it is quicker, easier, and safer to just separate the crankcase. I have used Dirko HT, Threebond 1184, Indian Head Gasket Shellac, and some blue automotive type silicone for reassembling the crankcase and all have advantages and disadvantages. My preference is Dirko since it is pretty easy to clean up when you make a mistake.

Needle bearings will always have a little bit of play, but it it is enough for you to notice you should at least consider replacing the bearing as well. BH-108 bearings are readily available, as are the 6119 seals.

Mark

Thankfully I already have a set of seals on hand, bought when I got my gaskets. I suppose at this point I need to decide whether to take this saw down all the way.

• There is enough play for me to hear a soft audible "clack" sound when wiggling the crank, although I can't really see the movement. (If this helps determine whether it needs a bearing, not sure how much play is normal)
• Would Motoseal work for sealing the halves? I picked up a tube of it already in case I have issues with the fuel tank sealing up.
• Do I need any sort of bearing puller or seal puller, and does this change depending on whether or not I split the crankcase? Same question for installation process for PTO seal, what particularly is different if I don't split the case?
• Is it worth doing both sides' bearings and seals if I do go this far?

Can't thank you all enough for the help in getting this far. VERY much appreciated.

 

[Jethro 2t sniffer]

The guy agreed to hold it as pending sale and I'm going Sunday afternoon. I don't know if it's politically correct but I'm planning to bring my pressure tester and I have an endoscope to look at the cylinder walls and exhaust ports. I haven't bought much on Marketplace but $150 is still a chunk of change, plus I'll be driving close to 300 miles. Any advice on anything else I should look closely at would be helpful. Thanks

As long as its hard to pull over with decomp out you'll be golden. If its not so hard to pull then your scope will show up the cylinder wall if it's still nice its just tired rings. Or it's scored up to hell. 150 for an 81 is a very good deal

 

[heimannm]

Motoseal is Threebond, you are covered there.

No "special" tools are needed to replace the seals if you split the crankcase. If you choose not to split the case, a small screwdriver can be used to get under the PTO side seal and pry it out, but do not damage the aluminum bore of the crankcase. Some seals by their design do not have a chamfered edge and can be very difficult to get started back into the bore. Unless the bore has a pretty generous chamfer I'd say you are way ahead to just split the case apart. I remove the flywheel side seals by drilling a small hole and using an old WalMart slide hammer with a sheet metal screw but they can also be pried out, again with caution so you don't damage the bore. I have never managed to scratch a crankshaft on a good quality chainsaw prying out a seal, but some cheap import (Chinese) saws have a crankshaft that is soft enough to be damaged by a screwdriver...

The flywheel side bearing (67905) rarely fails, but replacements are available if needed. The seals (67906) are also quite available. Max and I both have seals and bearings, I think Brian may have them as well. For the larger displacement saws the flywheel side bearing is different (63429) with a wider outer race and the seal presses into the outer race. Those bearings are hard to find and expensive if you do find one. The rolling elements (balls) in both bearing are the same but I think the wider outer race was selected to distribute the load over a wider area, like the PTO side bearing inserts used on the bigger displacement saws. If you are going to the effort of splitting the case I would always replace both seals and the PTO side bearing, probably $30-$40 worth of parts depending on where you get them.

Mark

 

[Jethro 2t sniffer]

Still probably my favourite saw

 

[Rallyeguy]

Still probably my favourite saw

Like Butter

 

[JSMississippi]

Motoseal is Threebond, you are covered there.

No "special" tools are needed to replace the seals if you split the crankcase. If you choose not to split the case, a small screwdriver can be used to get under the PTO side seal and pry it out, but do not damage the aluminum bore of the crankcase. Some seals by their design do not have a chamfered edge and can be very difficult to get started back into the bore. Unless the bore has a pretty generous chamfer I'd say you are way ahead to just split the case apart. I remove the flywheel side seals by drilling a small hole and using an old WalMart slide hammer with a sheet metal screw but they can also be pried out, again with caution so you don't damage the bore. I have never managed to scratch a crankshaft on a good quality chainsaw prying out a seal, but some cheap import (Chinese) saws have a crankshaft that is soft enough to be damaged by a screwdriver...

The flywheel side bearing (67905) rarely fails, but replacements are available if needed. The seals (67906) are also quite available. Max and I both have seals and bearings, I think Brian may have them as well. For the larger displacement saws the flywheel side bearing is different (63429) with a wider outer race and the seal presses into the outer race. Those bearings are hard to find and expensive if you do find one. The rolling elements (balls) in both bearing are the same but I think the wider outer race was selected to distribute the load over a wider area, like the PTO side bearing inserts used on the bigger displacement saws. If you are going to the effort of splitting the case I would always replace both seals and the PTO side bearing, probably $30-$40 worth of parts depending on where you get them.

Mark

I think I'm going to take it all the way down. Plus, as mentioned above, I can clean the carbon off the piston. I feel like I'll be more satisfied with the end result since I can better clean everything, and I'll know it's right once I'm all done.

Sounds like for parts, I just need to snag a new PTO side bearing if I'm safe not replacing the FW side bearing. Already have the 110260 and 67906 seals (thanks Brian for recommending I go ahead and have them on hand when I got my gaskets). Looks like I need to find myself a BH-108 bearing now!

 

[Jethro 2t sniffer]

Like Butter

They cut so nice. Can rev em can lug em can gently cut slowly n quietly up to a fence or a hinge without having to hold it wide like a modern saw. Are actually rather light Great av. Safer too in sketchy situations an 82cc Mac can drag the chain so slowly without stalling. And the early brakes I have trip with enertia far better than the huskies I run. Absolute gem of a saw the 81.

 

[Syncop8r]

If I had one dodgy bearing or seal I would be replacing everything, maybe that's just my OCD but I feel like if one component is bad then the others may not be far behind.
And you've already got it disassembled...

 

[Syncop8r]

The guy agreed to hold it as pending sale and I'm going Sunday afternoon. I don't know if it's politically correct but I'm planning to bring my pressure tester and I have an endoscope to look at the cylinder walls and exhaust ports. I haven't bought much on Marketplace but $150 is still a chunk of change, plus I'll be driving close to 300 miles. Any advice on anything else I should look closely at would be helpful. Thanks

The last thing I was interested in on Marketplace they were (supposedly) holding for me. When I went to arrange pickup they informed me they had already sold it.

 

[JSMississippi]

If I had one dodgy bearing or seal I would be replacing everything, maybe that's just my OCD but I feel like if one component is bad then the others may not be far behind.
And you've already got it disassembled...

That's how I feel. Knowing myself, I wouldn't be able to run it with full peace of mind. I'm not an anxious person with most things in life, but with mechanical things, I just am that way.

 

[Joe Crow]

Are there any visual instructions for separating the crankcase? I am new to this.

 

[heimannm]

There are four screws inside the oil tank (12-24x1-34) with a 5/16" hex head, and four screws outside the oil tank (8-32, length varies...) with a 1/4" hex head. I find it easier to access the fourth external screw if I remove the manual oiler. I sometimes replace the 8-32 flange head screws with socket head cap screws if the hex heads are damaged. I also have a 6 point 1/4" drive 1/4" socket that I've thinned the sidewalls to make it a bit easier to fit one of the screws in the crankcase that is buried in there.

Once the screws are out, use a plastic hammer or the handle of your ball pein hammer to bump the crankshaft and the two halves will separate.

I normally run a tap through the threaded holes and run the screws through a die before reassembling to get all of the old sealant and crud out of the way. I also put a dab of sealant on the threads, and try to get a little squeeze out around the flange head of the internal screws. Some saws were assembled with an aluminum washer and a rubber sealing washer under the flange head of the internal 12-24 screws and the rubber washers are usually destroyed. I have been using -009 o-rings on those screws and haven't had any failures yet. As I mentioned, a little dab on the threads as well as one time, and only one time I had one that was leaking through the threads of the internal 12-24 screws.

I think all of the 54cc saws have two round exhaust ports so there are no locating pins for the ring end gaps. I try to align them 120° apart and away from any ports or transfers, but I'm pretty sure those rings will migrate as the engine is running anyway. There is a small chamfer on the edge of the bore to help guide the rings back into the bore, but is still may require some rocking, pushing, and maybe even reaching in with a small screwdriver to get the rings compressed and the piston back into the cylinder.

Mark

 

[vinnywv]

This is a link to a sp81 engine assembly i did 2 yrs ago. Same concept for any of the 10 series. May help you take it apart. I also had a ground down socket to reach those tiny bolts.

 

[Rotax Steve]

When tinkering more on my 10-10 after disconnecting the fuel line I found the spring in it was messed up at the connection. How important is this spring or should I snip off the damaged area and push it back in?

 

[Rotax Steve]

You guys are going to get tired of me but trying to figure out my fuel leak problem I came up with an idea to use paper towel under both areas of concern. I use a red oil mix and figured I'd start it and look for red on the paper towel pieces.
When I went to start it; I could see lots of fuel in the intake and couldn't get it started. I don't know what's normal but it seems like too much. After pulling a bunch there was fuel coming from the exhaust.
Please help me, what's wrong?

 

[Rallyeguy]

Hi Steve,

Forgive me if you have already done the following. Pull the diaphragm cover (19) off the carb and verify that the diaphragm pin is connected to the arm that operates the needle,. If it is, pull the diaphragm off and verify the arm (24) is flush with the surface of the casting of the carb. If the lever is sitting proud of the casting of the carb (see pic), it might be continually dumping fuel into it as it is holding the needle off the seat.

I've also attached a diagram showing various diaphragms and fuel control valve layers so you can verify you have everything in the right order.

If you need an IPL for your saw, PM me your serial number prefix and model number and I'll send it so you have everything.

Brian

 

[Rotax Steve]

Hi Steve,

Forgive me if you have already done the following. Pull the diaphragm cover (19) off the carb and verify that the diaphragm pin is connected to the arm that operates the needle,. If it is, pull the diaphragm off and verify the arm (24) is flush with the surface of the casting of the carb. If the lever is sitting proud of the casting of the carb (see pic), it might be continually dumping fuel into it as it is holding the needle off the seat.

I've also attached a diagram showing various diaphragms and fuel control valve layers so you can verify you have everything in the right order.

If you need an IPL for your saw, PM me your serial number prefix and model number and I'll send it so you have everything.

Brian

Thank you. I rebuilt the carb already and took it apart again to check and it seems to be correct. When I removed the diaphragm there was quite a bit of fuel in there still and the diaphragm was saturated, not sure how normal that is? Took a photo and did this video incase someone asked. How does it look to you?

 

[Rotax Steve]

Hi Steve,

Forgive me if you have already done the following. Pull the diaphragm cover (19) off the carb and verify that the diaphragm pin is connected to the arm that operates the needle,. If it is, pull the diaphragm off and verify the arm (24) is flush with the surface of the casting of the carb. If the lever is sitting proud of the casting of the carb (see pic), it might be continually dumping fuel into it as it is holding the needle off the seat.

I've also attached a diagram showing various diaphragms and fuel control valve layers so you can verify you have everything in the right order.

If you need an IPL for your saw, PM me your serial number prefix and model number and I'll send it so you have everything.

Brian

Oh! I get what you're saying now! Boy do I feel stupid. I've been rebuilding HDB carbs a lot lately which only have a flat tab and haven't rebuilt an SDC in a couple years. I forgot the forks on each end have a purpose. It was not attached - will that solve things?

 

[heimannm]

The spring is in the fuel line to keep it from developing a kink that would pinch the fuel line closed. Try to reinsert it into the area where the sharp bend occurs.

Once you assemble the carburetor correctly, pressure test it at the fuel inlet to confirm that it holds pressure.

Mark