McCulloch 250

[Coralillo Lo Pro]

On and off when I have nothing else on my plate, I try to get my 250 I picked up for $50 to run better or run at all. Figured out by now the 24" bar with roller nose was about worth it alone. Put a chip in the ignition and thought I was still getting erratic spark cause I couldn't keep it going more than a couple minutes without it dying and not wanting to restart. Then I remembered I'd only ultrasonic cleaned the carb, I hadn't rebuild it, so I got a kit and did that. Still no luck but think I gave up on it too easy. So I got a second hand coil thinking it couldn't be anything else and put it in and that showed the same kind of erratic spark on the tester, so I think that's just a crappy tester. Wasn't doing anything for a bit even w holding the throttle down while starting, but finally got some sputtering and eventually got it to catch and rev and it roared to full speed better than it ever had before and held there. For a "slow rpm" saw, it revs faster no load than I expected it to.

But wasn't idling worth a damn til I cranked up the idle screw some. Just when I thought I had it about right, and let it idle a long time to make sure it kept going, I'd rev it up there and it wouldn't come back down to idle but just keep screaming til I frantically backed off the screw and then it would die. Will try tuning it tomorrow and see if I make some progress. But it was nice to hear what it's supposed to sound like for the first time, really revving. And get a setting where it would idle. Now to just make it do both on the same setting.

 

[Mad3400]

Great Deal!

I had a couple 250s and none of them would rev anything close to a newer saw, even without a bar hooked up, but were obnoxiously loud!!!

I would set the carb a bit fatter on the L&H jet and double check the fuel filter & line, as well as the crank seals.

Mad3400

 

[Coralillo Lo Pro]

Great Deal!

I had a couple 250s and none of them would rev anything close to a newer saw, even without a bar hooked up, but were obnoxiously loud!!!

Yeah, nothing like a newer saw but still plenty fast enough to cut well. Specs refer to max rpm of the 250 as only 6000 but I think that’s just where it develops max power being such a low end torque beast. Curious what the max no load is - 9000? 10000? Far below the 12-13k of a modern saw for sure. No manufacturer used to bother w no load numbers. They would just list the rpm where the saw developed max power. Now people are obsessed w no load rpm for some reason. The 250 is obnoxiously loud - trying not to subject my neighbors to too much testing.

 

[heimannm]

There are some square o-rings on the H and L adjust needles of the Tillotson HL carburetors that can fail over time. Make sure your adjustment screws are not moving when the saw is running. If they are, you can replace the OEM parts with some small o-rings to prevent the needles from wandering on their own.

The same can happen to the idle speed screw, it seems at times there are some vibrations on the old McCulloch saws. A stiffer spring under the idle speed screw may be required.

Mark

 

[Coralillo Lo Pro]

There are some square o-rings on the H and L adjust needles of the Tillotson HL carburetors that can fail over time. Make sure your adjustment screws are not moving when the saw is running. If they are, you can replace the OEM parts with some small o-rings to prevent the needles from wandering on their own.

Mark

Thanks, Mark. I noticed the o-rings on the needles and made sure they were okay. Will check the idle screw, I did initially have an issue remounting the carb with getting it to spring back into place but thought I'd resolved it. I should have pressure tested the crankcase last time I took the carb off. No idea if the seals are any good or not.

 

[EchovsStihl63]

Something else to watch when you are in the carb is the needle and seat, they need to be replaced as a set and the lever arm properly adjusted. I failed to do this and caused a very poor running saw. Once I fixed that the saw ran great, until it sat for a week and wouldn't pull fuel any more, haven't bothered to see what the problem is yet.

I'll get to put it in a log one day.

 

[heimannm]

I have noticed on several projects the NOS rubber seats would swell up drastically when exposed to modern fuels completely blocking the flow. I grabbed another from my stash and they worked just fine. I'm sure some of the parts I have on hand are 50+ years old and still work as intended.

Mark