Help for Mac 250 and Stihl 036 Pro

[Bronzebird]

Hey guys I'm new here...

I'm in the middle of a old Mac 250 rebuild. The saw was pulled from my uncle's trash pile. It had 90 psi compression with spark. Cylinder and head is clean. So I ordered a set of Caber rings.

If someone can post a link or email me service manuals I can check the service limits on this old saw. I have not touched the Stihl 036 Pro yet but will need info on that saw too.

I have rebuilt Dirt Bike engines years ago and found a new itch to scratch helping a friend in need of "rebuildable" saw. (Stihl was found cheap)

I have a homelite 330 that I bought new in 1985 and replaced the intake boot last summer. I made a YouTube vid that has helped others. The Mac 250 vid is in progress for the tear down.
My YouTube user name is Bronze Bird, AVI is horse pic.

Thanks for any help on these rebuilds.
-Bronze

 

[Bronzebird]

Solid Info: The Beg for Manuals Thread

Wow, lighting fast response today...got all my saws covered.

Thanks GermanOak!





EDIT: first attempt to post a pic of rebuild

 

[Bronzebird]

Still waiting on parts ordered...dang

Well I guess the Holiday rush is what it is...I got the cylinder and pistion for the McCuloch 250 meassured and they are clean and tight with no scoring!

 

[Bronzebird]

Ring a ding ding, parts came in excellent shape!

The heavy cardboard packaging is primitive but effective. Not a bend in the board...whew!

View attachment 269183

 

[Bronzebird]

Merry Christmas!

Manual Oil Plunger had a melted O-Ring turn to goo...I hit the hardware and auto parts for replacement o-ring and nothing. So I improvised with a homemade fix...

-lubed oil port with thin coat of 100% clear silcon grease.

-Apply silcon gasket goo to plunger

-Lightly twist plunger into hole leaving a 1/8th inch shoulder to grasp for extraction after 24 hours of dry time.

-The results is in the pic and it should work. If at anytime my trials turn into errors, I will update this thread with a fix. (Hunt continues for the odd size O-Ring)

View attachment 269583

The old O-Ring black ressidue was attracted to the silcon gasket maker goo. Other than that; the extraction was a breaking turn left for a hair, another hair turn to the right and the plunger was free with no mess left in the oil port.

 

[Bronzebird]

Got the new square rings installed in the cylinder today...

The rings are meassured square and no location stop pin in pistion ring grooves and no V-angle gap at ring ends.

I touched the inside ring corners with fine grit wet/dry as they were razor sharp and would scratch the heck out of the piston when installing. The new ring gap was not meassured but eyeballed to be twice the lesser gap of the old rings which looked gapped at 8 or 10 thousandths of an inch...the saw had 90 psi and looking forward to new pressure test! Fingers crossed for 150-160 psi before break-in of rings.

Home cut gaskets is labor intensive but "available"..lol

 

[timbrjackrussel]

Manual Oil Plunger had a melted O-Ring turn to goo...I hit the hardware and auto parts for replacement o-ring and nothing. So I improvised with a homemade fix...

-lubed oil port with thin coat of 100% clear silcon grease.

-Apply silcon gasket goo to plunger

-Lightly twist plunger into hole leaving a 1/8th inch shoulder to grasp for extraction after 24 hours of dry time.

-The results is in the pic and it should work. If at anytime my trials turn into errors, I will update this thread with a fix. (Hunt continues for the odd size O-Ring)

View attachment 269583

The old O-Ring black ressidue was attracted to the silcon gasket maker goo. Other than that; the extraction was a breaking turn left for a hair, another hair turn to the right and the plunger was free with no mess left in the oil port.

I can't remember what the oil plunger O ring looks like. The oiler on my MAC15 was like a small version of a car engine umbrella valve oil seal. I have a few MACs 250 , I-40 etc. and will have to take a look at the oil pump.
I have seen some plumbing repair kits that have very interesting plunger seals in them. Parts for a single lever kitchen tap (non cartridge type) have a plunger about 11m.m. in diameter. Perhaps it may be what you need.

Plumbshop Single Lever Repair Kit | Canadian Tire

 

[timbrjackrussel]

I can't remember what the oil plunger O ring looks like. The oiler on my MAC15 was like a small version of a car engine umbrella valve oil seal. I have a few MACs 250 , I-40 etc. and will have to take a look at the oil pump.
I have seen some plumbing repair kits that have very interesting plunger seals in them. Parts for a single lever kitchen tap (non cartridge type) have a plunger about 11m.m. in diameter. Perhaps it may be what you need.

Plumbshop Single Lever Repair Kit | Canadian Tire

A Peerless Diveter Valve kit, for a single lever kitchen tap, PlumbShop # PS2172 has a promising seal in it as well

 

[Bronzebird]

I can't remember what the oil plunger O ring looks like. The oiler on my MAC15 was like a small version of a car engine umbrella valve oil seal. I have a few MACs 250 , I-40 etc. and will have to take a look at the oil pump.
I have seen some plumbing repair kits that have very interesting plunger seals in them. Parts for a single lever kitchen tap (non cartridge type) have a plunger about 11m.m. in diameter. Perhaps it may be what you need.

Plumbshop Single Lever Repair Kit | Canadian Tire

Thanks for the parts ideas...I wonder how long the rubber would hold up in bar oil? The old o-ring at the front of the plunger pump was melted like tar, the back o-ring is good as viewed in the pic. I found some silicon gasket compound to come with a warning not to use with fuel or oil.

A Peerless Diveter Valve kit, for a single lever kitchen tap, PlumbShop # PS2172 has a promising seal in it as well

Yep, the o.d. plunger valve is 9.3mm and i.d. is 6.3. For now... I will give the MacGyver fix a shot. I will be in Kent, WA this Thur/Fri and stop by Cascade Gasket company. I used to have some friends that worked there baking gaskets for Boeing and other companies.

 

[Bronzebird]

Gaskets made, Crank Shaft and Magneto side case installed

How I make Gaskets:
The Magneto/Flywheel side case Gasket was designed from pointed metal dividers used to measure the hub diameter. Then center the hub size on the fiber gasket material and push dividers into the gasket to mark the diameter. Then rule a straight line from point to point on the gasket. Reduce the dividers by 50% and check for hub center location by walking the dividers and adjust to find center of hub. Then Scribe the gasket by spinning the dividers from hub center to make a compass outline for hub hole. Then use razor knife to cut hub hole.
I applied a thin layer of silcon gasket sealent on hub flange and placed the gasket over the hub and made a good imprint of hole pattern onto the gasket. The gasket fit was snug and care was taken to work "slowly" moving the gasket into place and removal. Then the holes were cut following the imprint with a razor knife and trimmed gasket size to leave about 1/8"th overhang on gasket. The idea is that the wider gasket will be less likely to break when installing for final fit. Remeber to wipe off sealent from hub and gasket before the sealent drys. Use a pen or pencil and mark the gasket for indexing to a specific screw hole on imprint. This will take out any guess work on matching gasket to original imprint hole positions. I used 1/32" fiber gasket material from a large rolled sheet from the auto parts store. Make sure to use proper silcon sealant if used in fuel tank and oil tank, most silcone sealants are not compatiable with fuel/oil seals. After the side case screws were mildly/lightly torqed, they will be retorqed after the sealant drys for 24 hours.

Needle Bearings embbed in greased yoke:
It should be noted that the saw handle is clamped with a rag around the handle to hold the piston cylinder in in vertical position on the bench. The piston is at top dead center of stroke and the crank was installed with the side case. I installed the connecting rod clamp with bolts to the cranshaft without the needle bearings, all surfaces have a layer of grease to prevent scratching. I then rotated the crank to pull the piston to bottom dead center of stroke. Removed the finger tight bolts and clamp. Reapplied an good layer of grease to hold 12 needle bearings in connecting rod yoke and 12 needle bearings into the yoke clamp. Make sure all needle bearing are inline side by side and centered. As the bolts tighten the grease will extruce from the yoke. I checked with finger tips and tweezers that needle bearings are not skewed and continue to torq and check...Bolts are tighted by hand with allen wrench, then a wrench is applied to allen wrench for leverage to make final torq.

 

[Bronzebird]

Mag, clutch, crank case base, and fuel tank

On the Magneto/flywheel make sure the starter pauls are in the operating position before placing the flywheel on the tappered keyed shaft. To lock the crank shaft from turning I pushed a piece of rope through the spark plug hole and out the exhaust port. Note that chamfered ports will prevent the rope from being cut when torqing the clutch and mag locking nuts. Never put pressure on the cooling fins on the Mag, they will break and cause out of balance vibration problems.

The clutch was cleaned and old grease removed. New grease applied to clutch shaft bushing.

Crank case and fuel tank was sealed with Permatex item #85420 which is fuel and oil resistant. All screws and bolts are lightly torqed and sealent is allowed to dry before final torq is applied. Inside the fuel tank the 4 big bolts are sealed on the bolt near end of bolt head, excess sealant is wiped off before it dries. Fuel cap is left off while sealant dries. During the drying time I just wash up and walk away from the project then come back and make the final torq. I would hate to see someone forget to make final torq to gaskets, so leave yourself a reminder note if you are prudent.

Looking forward to putting the starter cover on when the case gasket sealant is dry and test the compression...which reminds me, I should put a new cord on the starter!

 

[Bronzebird]

Ignition and Carb adjust before START UP

So I thought it would be worthy to mention to clean the points with fine grit sand paper before the magneto is installed and set the gap .015"-.018" thousandths. Setting the gap with the points open is achieved by observing the gap opening by turning the crank shaft. Notice the keyway on the tapper shaft is pointing just in front of the breaker electrodes. Clean all metal to metal contact. This includes the condensor mount and screw, coil pick up mount, screws, and lead contacts male and female. Magnets and fly wheel surface that mate with the coil pick ups, everything should be shiny clean. I had weak orange spark before the rebuild, now it is firing white spark accross spark plug spark test with the same old plug. Mag adjustment gap was set with brown paper bag folded in half which meassured at .015" with the understanding that paper thickness may vary, use a caliper to check your flexible gauges on the round surfaces.

Carb adjustment screws was found to 3 turns out from bottom on the high & low screws. I reset at 1.5 turns out.

Idle adjust was high, about half way in on threads. I backed off till zero with no slack and turned in one turn.


START UP: Compression was stupid low before running the saw and it would not hold pressure during the test of several times. I had a bad feeling in my gut...and forged on with 40:1 fuel up on a saw that had a hot spark. I used a spray bottle and gave a nice misting spray into the carb, turned the choke on full and gave a pull and nothing. I redid the spray mist and turned the choke back on and gave a pull and got a POP! My heart was not heavy and gave her another shot of fuel and kept getting sputter. I'm thinking the air in the fuel line will be out soon. I got the saw running and kept it running by using the choke on/off to maintain idle. As the saw warm up the RPMs picked up without the choke on. I adjusted the L-screw out 1/8th turn and the RPMs lowered to slow idle. I ran the saw for about 3 minutes and was no longer concerned about the compression. I will check the compression again, but the saw has a raw 1970's crisp pop and looking forward to hi rpm carb adjustment under a load while cutting. I never was a fan of max rpms without a load on the motor.

Conclusion: this rebuild did not require any special tools to replace the rings. Impact driver & socket set, rope for piston lock, feeler gauges, digital calipers, fuel resistant gasket sealant, roll of fiber gasket, razor box knife, and I used a wood chisle to remove old gasket material (keep chisel on the flat side with a low angle of attack to prevent digging into the soft metal. I hand sand the chisel with 100 grit to remove any burrs that cause nicks). The last item requried is patients and take lots of pics of how the saw looks before removing something. For example, take a pic of the inside of the clutch assembly with spacer sequence.

I have another 250 that was offered to me that needs a chain and bar. I need to pay for shipping if I want the saw that is not running. After today it is a big YES!

 

[Bronzebird]

Looking for after market chain and bar for the 250

Here is a vid of the saw getting broke in, the bar & chain needs to be replaced before I put the saw to work. The bar is good shape and the chain is stretched at max service limit. I'll be saving the old bar and chain to keep the saw "stock" when I sell the saw, someday...


[youtube]0iO9Qr7F2yE[/youtube]

 

[Bingo]

mac build

Very nice work on the Mac. Once tuned you'll be happy. Makes me think I'm at a go-kart race again...

 

[Bronzebird]

Fun time burning a tank of fuel cutting Oregon Fir

The saw chain is not too sharp but usable with stretched to max service limit.

I ordered a new clutch hub and .404 pitch sprocket for $15...I'm stuck on what kind of new chain to get? The old chain is full chisel on a 20" bar.

I posted this replacement question in the Mac thread. Let me know what you think is a good cutter set up for the 250 before I talk to a "salesman" and lay some money down...

thanks!

 

[Eccentric]

The saw chain is not too sharp but usable with stretched to max service limit.

I ordered a new clutch hub and .404 pitch sprocket for $15...I'm stuck on what kind of new chain to get? The old chain is full chisel on a 20" bar.

I posted this replacement question in the Mac thread. Let me know what you think is a good cutter set up for the 250 before I talk to a "salesman" and lay some money down...

thanks!

Are you cutting a lot of skidded/dirty wood? If so, then I'd suggest semi chisel (such as Oregon 27X). If not, then I'd suggest chisel. Either way, you should go with a full comp (not semi-skip or skip) loop on that short bar.

 

[Bronzebird]

Are you cutting a lot of skidded/dirty wood? If so, then I'd suggest semi chisel (such as Oregon 27X). If not, then I'd suggest chisel. Either way, you should go with a full comp (not semi-skip or skip) loop on that short bar.

Thanks for the semi chisel full comp reccommendation.

I am looking at mods needed for a modern hard nose bar? Then I can go with a longer bar...any help here would also be appreciated!

 

[Eccentric]

Thanks for the semi chisel full comp reccommendation.

I am looking at mods needed for a modern hard nose bar? Then I can go with a longer bar...any help here would also be appreciated!

A large Husqvarna mount bar can be made to work. Slot needs to be enlarged a tad, and you may have to modify the oiler and/or adjuster holes a bit. There are plenty of large mount McCulloch bars floating around still however. Ask around here and check feebay. Most of us want to hang onto our longer bars in this mount (28" and longer).....but finding 24" and shorter hardnoses isn't dificult...

 

[Bronzebird]

A large Husqvarna mount bar can be made to work. Slot needs to be enlarged a tad, and you may have to modify the oiler and/or adjuster holes a bit. There are plenty of large mount McCulloch bars floating around still however. Ask around here and check feebay. Most of us want to hang onto our longer bars in this mount (28" and longer).....but finding 24" and shorter hardnoses isn't dificult...

Thanks, I will look around for large mount bars for Husky's and modify to make work.

 

[RandyMac]

There are tons of original bars.

3 McCulloch Chainsaw Bars and A Chain from Mac 250 Saws 18 20 22 | eBay

I have several in storage.