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

[S250Usesr]

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?

 

[gerrywoodsy482]

Check the fuel lines for cracks or damage. Check the spark plug and ignition system. If the saw is smoking during pulling, it could indicate incomplete combustion.

 

[S250Usesr]

Check the fuel lines for cracks or damage. Check the spark plug and ignition system. If the saw is smoking during pulling, it could indicate incomplete combustion.

Well...the fuel lines looked good a year ago when I patched the hole in the tank (learned a lesson about ethanol in old motors). Those fuel lines seem to be unavailable, but found some used ones attached to tanks on e-bay. Good point on the ignition tho...since it runs and idles I hadn't thought about something getting hot and causing problems there. I should go through that next. I wonder if anyone knows if a chip is a good idea on this saw...I think I saw more than one magnet on the flywheel. Thanks for your advice...looks like it is dis-assembly time. Maybe next Saturday.

 

[heimannm]

I have NOS fuel lines from the tank to the carburetor (67094), $2.00 + shipping.

Check compression, could be on the low end and things loosen up a bit when it is running and warm.

Mark

 

[S250Usesr]

Had a day to play with the saw...Fuel lines are pliable and don't seem to be cracked anywhere.
Fuel was getting in the airbox from the back end of the carburetor ...I just couldn't see it running out since it was a smooth flow and probably dripping underneath where I can't see.

• Went through the carb again...went back to the old needle and seat...since there wasn't anything wrong with them. Now there's only an occasional drip in the airbox.
• Sealed the bowl plug and the fulcrum screw..
• Compression is 90psi.

It started, ran, tuned L , H and Idle...All good! ....so I thought.

• Picked it up and pretended to saw some branches off a log....boom, it dies.
• Decided to go through the ignition....set the points and flywheel gaps to spec. .018 and .008 respectively. (Points were originally less than .010, resistance is 0 Ohms when closed.)
• Now it won't start....gave up after a few pulls....spark tester glows.
• 4 hrs. later, I went to check my spark plug type (research says it should be the antique J8J..I have a J8C)...cylinder is FULL of fuel. So much, that it locks up if an attempt is made to pull it one more time.

Grrrrr. Where's all this fuel coming from? (I don't think the carb can even hold that much.)

 

[S250Usesr]

One more question...Can anyone tell me about the magnets on the flywheel?
There are three...2 small Strong ones on one side, 1 very large, weak one on the other side.
Does this large weak magnet mean my flywheel is shot, and the ignition won't work right?

 

[heimannm]

I believe you will find the 1 large "weak" one is just a counterweight cast into the flywheel and whatever you are checking it with is slightly magnetized.

Mark

 

[S250Usesr]

I believe you will find the 1 large "weak" one is just a counterweight cast into the flywheel and whatever you are checking it with is slightly magnetized.

Mark

Thank you, Mark! You were spot on. My big old screwdriver seems to magnetize easily. Do you happen to know if I can use one of those ignition chips on this saw?

 

[heimannm]

You can use a chip, disconnect the wire at the coil (coming from the points & condenser) and connect the chip. Ideally the chip will be somewhere that gets good airflow for cooling and away from the coil itself. Others have commented that having the chip too close to the coil leads to failure. I don't use the chips very often and have not had the experience of one failing but I try to keep them away if possible. On many saws you can put the chip where the condenser used to be.

Try the search function and you can find other information related to points replacement chips.

Mark

 

[Lightning Performance]

One more question...Can anyone tell me about the magnets on the flywheel?
There are three...2 small Strong ones on one side, 1 very large, weak one on the other side.
Does this large weak magnet mean my flywheel is shot, and the ignition won't work right?

You might have fuel passing the pressed in brass seat for the needle pin. Removing them is a big pita but if it needs it you can try seating it again with a tapered tool. You might need to check the arm height then reset after cutting a new seat in there. Look down in that seat area again.

 

[heimannm]

The 250 uses an Tillotson HL carburetor, the seat for the metering needle is screwed in and had a replaceable rubber seat.

Mark

 

[S250Usesr]

The 250 uses an Tillotson HL carburetor, the seat for the metering needle is screwed in and had a replaceable rubber seat.

Mark

I can see the rubber from the bottom side once I screw it out..HL 63G. I don't think I've seen that rubber seat available anywhere.

 

[S250Usesr]

Magneto has 1.2 ohms on primary....6500 on secondary. Points have 1 ohm from the screw to the case. Don't seem to have spark now. That chip is looking like a good idea.

 

[S250Usesr]

...forgot to mention the condenser is around 300 pF.

 

[heimannm]

I normally find the condensers right around 0.2 - 0.22 µF, you might want to check yours again. I've tested dozens and they are all right there.

Roll the engine over and check to be sure the points are making and breaking, you will need to disconnect the condenser and points lead to know for certain.

Mark

 

[S250Usesr]

I normally find the condensers right around 0.2 - 0.22 µF, you might want to check yours again. I've tested dozens and they are all right there.

Roll the engine over and check to be sure the points are making and breaking, you will need to disconnect the condenser and points lead to know for certain.

Mark

Good advice Mark, Thanks! The original gap on the points was <.010 didn't bother to see exactly how much less ....I set the gap to .018. The points did close, but the resistance seems too high. Research suggests that resistance should only be .1 ohms...I had 10x that. That condenser was probably the last thing I measured before my meter lead broke off at the solder joint. I'll have to try measuring all over again once my new leads show up, just to be sure. (I would ordinarily fix a solder joint, but never liked that set of leads anyways..)

If you don't know of a better place, the folks over at eccarburetors.com say they should be able to fix me up with a new needle and seat that will work....once I take it out again and measure it.

 

[heimannm]

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

 

[sean donato]

If your points contacts are dirty they will have high resistance as well. I'd skip the rocket chip and get a new set of points. Call it a day.

 

[heimannm]

Points are 50076->88806, I have NOS points available for $5.95 + shipping.

Mark

 

[Okie]

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.