McCulloch S250 Headache...or maybe heart attack. What to try next?

[Okie]

Here is a little bit of general info about them Tillotsons.
Be really careful when installing the carb. If the carb to manifold adapter is not lined up properly you WILL BREAK a ear off the manifold or the carb, most generally the engine ear and you are then SOL. When you see them saws for sale always look at the ears, some are broken/cracked and the seller just stuck them in place hoping the buyer would not notice on a non running saw.
McCulloch chainsaw carbs types



If you are asking about Carbs for the old Mac saws here is what I've used and will interchange, from my Mac notes.


These numbers and letters are stamped on the carb and usually into the upper left ear of the carb and can be seen with the carb in place.
The tillotson HL63D, E, and A can be used interchangeable and use same kit and can also be used in place of the 87D, but the 87 D cannot be used to replace the 63A, D, E,

because the 87D does not have a choke butterfly inside the carb. (the choke assembly for the 87D carb is made on the saw air box)



And these Tillotson carbs can be used to replace the carbs that were made by McCulloch but a throttle linkage kit will be needed.

I seen some mod carb kits at chainsawyr.com every once in awhile for the old 1-40, 1-50, 250 series of Mac saws. They might still have the OEM Mac service manual download available at a reasonable price. If you get the download install it onto a CD disk for later use and shop use before your computer crashes and you lose the download.



The 1-40, 1-50 series of Mac's came out with approx 3 different types of carb's during their production, a HL87D, HL63A, D, and E and a carb made by McCulloch and I think

I’ve heard of some Mac 250’s that use a Tillotson HL63F carb which uses a RK106 kit.

maybe one type of carb referred to as a Bullfrog carb.(it's bottom looks like a bullfrog belly)The Tillotson carbs will bolt up and replace the Mac, bullfrog and flat back carbs with correct linkages.



The Tillotson carbs are user friendly to repair and service info and parts lists readily available at the Tillotson website, look at HL series carb.







The kit for the Tillotson is a RK-88HL at about $10 from flea bay

 

[S250Usesr]

If they have material for the seats that will work with modern fuels (including ethanol blends) I would be interested in buying a few sets myself.

Mark

I found a new 012339 NOS that looked shiny in the picture on e-bay..we'll see.

GBDistribution (07-229) looks like it could have the rubber seat in it ...$8, maybe it will fit?
Discount Marine Parts DI 22134 (massive kit) mentions having a new nitrile seat "Because the brass seat is not available".
You may want to check these out.

 

[S250Usesr]

Some Mac tips from experience with that one.

For one get the new Points and condenser from Mark. A $20 chip is most generally a waste of time and money due to non reliable and timing will sometimes be off and the flywheel key will need to be removed to get a run, although I keep couple of the old NLA Atom chips around just as a test to see if points and condenser are the issue. The old electronic ATOM chips were really good/reliable and color coded for different engine types.
About your fuel leak. If you are still trying to use the old Mac fuel line clamp at the carb it will leak/seep. Get a itty bitty hose clamp. Anytime you see fuel in the air box you will have to get that corrected or you will most likely never get a good reliable run.
Next about the Mac tip test. When you get to where it will run at idle then do the tip test.
Also when first adjusting the idle jet take the bar/chain off or at least leave the chain loose. Why: because if the clutch side seal is leaking it leaks worse when the chain is tightened. Sometimes one will idle and run good until the bar and chain is installed and the chain tensioned and the low jet adjustment changes or becomes more erratic.
The bearing is still good, the old seal is dried out.
You can replace this seal by doing careful removal. Might even see a you tube about such.
You can confirm leaking seals by doing a pressure test using not over 5 psi and slowly rotating the crankshaft and using soap/water.

You can find good info at the tillotson site about your carb.
In my next post is some Mac carb info that I filed:
With careful shopping you can sometimes find a good replacement Tillotson on flea bay, but lots of bad ones also. Most all will require a kit.

Clamp???...What clamp? Mine just slips on and off...rubber's pretty tight on the barb. Lookie thar...there IS supposed to be something on there.


I'll have to see what I can find. Probably have something laying around. Thanks!

Seal test?....hope it doesn't come to that, but thanks for the info!

 

[Okie]

You asked.:
Clamp???...What clamp? Mine just slips on and off...rubber's pretty tight on the barb

The OEM clamp #5 was just a slit brass ring on a rubber fuel line and the old rubber line was a large O.D. and would harden and hairline crack internally and leak and then when a person replaced the fuel line they would re-use the old clamp due to the restricted area mainly just relying on a friction snug fit of the fuel line onto the barb which later results in a seep leak because the friction barb fit is not enough after awhile especially when the engine starts running
Your clamp might be ok, I'm just saying that this is the source of a seep and not easily seen and sometimes won't seep until the saw is running. It also results in the carb's pump sucking air and not getting a strong fuel supply when really needed under load. What I've done is get a small stainless 1/4 inch clamp and arranged it so as it can be snugged up with a screwdriver.
I'm mainly also saying that any fuel at all in the air box is not a good thing for getting a good run especially under load.

You mentioned tilt test, erratic idle when tilting.. Have you pressure tested the crankcase? Pressure testing the carb is also a good thing.

 

[S250Usesr]

It's time for an update...20 Degrees outside and it's time to warm up! This saw running!!

Learned a couple of things along the way...
Those light bulb spark testers....JUNK!...for this purpose anyway.
Both light up with no sparkplug attached!!
Once I got that figured out, I just threw the old sparkplug away and got a new one...Test with the ohm-meter on the sparkplug showed it was all good, it wasn't.

Points and condenser..
Condenser was 278 pF...cleaned points to zero ohms, they look good, they open and close, don't have any shorts where there shouldn't be...Still didn't work reliably. Had a chip coming in the mail already, so I installed it.

Saw starts on the first pull now.

One little bothersome thing left...Idles and idles some more. Saws on the left side, right side and horizontal....But point the bar straight down 80-90 degrees and it IMMEDIATELY floods if its idling, and will flood after 10 sec if wide open. I can level it out between wide open cuts and get the work done though.
View attachment My movie 1.mp4

 

[Okie]

Yes, light bulb testers will flash on a weak ignition. Just use a spark plug gapped at .030 or.040 or a Briggs type spark tester.
The 278pf (picofarad) condenser reading shows bad. should be in vicinity of .18 uf

Hope you have better luck with the Nova chip than I.
The chip let you know that the points condenser is your ignition issue.

When the saw is pointed straight down and starts getting rich is a ??????
Would be good if you had another carb to test with.
Make sure the in tank fuel filter is stay submerged and the tank vent is ok.
Some of them Macs had two different gas tank vent arrangements, one was the gas cap the other I forget how????. Been awhile since I seen the non-cap vent type. At one time I could tell the difference by glancing at the caps. If someone installs a non vented cap where a vented cap should be would cause a problem. (or a esxternal non-vent cap had the vent clogged.

 

[S250Usesr]

Yes, light bulb testers will flash on a weak ignition. Just use a spark plug gapped at .030 or.040 or a Briggs type spark tester.
The 278pf (picofarad) condenser reading shows bad. should be in vicinity of .18 uf

Hope you have better luck with the Nova chip than I.
The chip let you know that the points condenser is your ignition issue.

When the saw is pointed straight down and starts getting rich is a ??????
Would be good if you had another carb to test with.
Make sure the in tank fuel filter is stay submerged and the tank vent is ok.
Some of them Macs had two different gas tank vent arrangements, one was the gas cap the other I forget how????. Been awhile since I seen the non-cap vent type. At one time I could tell the difference by glancing at the caps. If someone installs a non vented cap where a vented cap should be would cause a problem. (or a esxternal non-vent cap had the vent clogged.

The gas cap has a sintered metal mesh...no valve as far a I can see. It does leak when tipped sideways on a full tank. (I cleaned it and got all the sawdust out of the mesh with some carb cleaner and compressed air.)

The HL63-G carb on this saw has a potted main jet...looks like epoxy of some sort under in instead of a welch plug. I'd try cleaning the main jet, but I'm not sure how to glue it back in. Can this be done?

 

[djones]

So I have this Super 250 with a Tillotson HL-63G carb...Was my Dad's saw before he gave it up.
The saw will run and cut, will idle and rev all day when level and not under load....but:

• Saw for a while (4-5 12" cuts) and it will quit....won't re-start till it cools off. Smokes a little while pulling (insert heart attack here) but won't start.
• Tip the saw forward from level while idling, it will quit after a bit.
• Leave it sit over a couple of days...it's hydro locked..have to remove the plug and dry out the cylinder before I can pull it.
• Till it warms up some, fuel leaks from somewhere and puts a good layer in the bottom of the air box. (Can't see where it's coming from). Gaskets around the fuel pump area seem wet though.

I've tried the following:

• Removed H and L needles and replaced mashed rubber something or other with small o-rings.
• Removed welch plug on inside and blew air through all ports (needles, seats, etc..removed)
• Replaced the old non-forked inlet control lever with a forked one, along with new needle and seat. (adjusted lever flush)
• Checked, cleaned fuel filter.
• Replaced all gaskets and fuel pump diaphragm.

What should I try next? (knowledgeable ideas much appreciated!)

• I think my next goal is to find out where the fuel is leaking from (maybe the inlet valve fulcrum which screws in from outside?)
• Maybe take the fuel tank apart and check for cracks in the fuel hose?

View attachment 1149034

Any motor that runs for a short time and then quits that requires a cool down time should have it's coil looked at and checked. Most likely it needs to be replaced.

 

[S250Usesr]

Any motor that runs for a short time and then quits that requires a cool down time should have it's coil looked at and checked. Most likely it needs to be replaced.

Tried that..different coil works the same..It is definitely flooding...I have to pull the rope with the throttle full open till it'll ignites...then let it smoke and sputter till the extra is gone...

 

[Okie]

Just couple more hints:

Go to post #17 and ask Mark. Send him a PM. I've not had any experience with the 63-G

I've worked on the A,D,E, and used them interchangeable, but not the F or G stamped carb's

Ask Mark if a A, D, or E would sub or his opinion of yours, etc.
I've bought and seen and good rebuildable 63 A, D, and E on fleece bay quite often at a reasonable price. I stay away from the ones that has the screws heads all buggered up and lots of afterbirth where Bubba and Rube have been. When I say reasonable, in the vicinity of $25-$30 and they require a kit usually. I also avoid the word vintage and overpriced and look at the feedback of the seller. 9proceed with caution)
You might try the want to buy section for a carb on this site. These want to buy forums on this site are more trushworthy than Fleece bay.
.

 

[S250Usesr]

Well, just wanting to be through and clean this one up!
The problem was...drumroll please...the oiler!
Yes, there is a little cap on the end of the oiler that was probably slowly coming loose. Fuel was running through it, past the impulse piston, through the impulse port, into the case. It had a 2nd carburetor!
Tip the saw down, or to the side, fuel covered the oiler and it flooded.
Purchased a NOS oiler from Mark ...good to go! So happy! Sawing again!

 

[cbfarmall]

I always wondered about having an oil pump inside the fuel tank. Mcculloch was the only one to do that as far as I know. Good catch, that would have driven me nuts.

The little cap you are referring to, is that welch plug?

 

[S250Usesr]

I always wondered about having an oil pump inside the fuel tank. Mcculloch was the only one to do that as far as I know. Good catch, that would have driven me nuts.

The little cap you are referring to, is that welch plug?

Yes...looks like a welch plug..but is thick. Looks like it may have been epoxied in place to seal it. Corrosion got to my oil pump housing (ethanol gas...won't do it again!) it ate the little lip the plug sets into...the fuel got around the plug.