McCulloch Super 250 Bizarre Idle Fuel Issue

[camer_1107]

Can you explain your question?

AND are you still using the 404 chain?

Be sure you keep the H jet adjustment on the rich side. (rich is CCW for the 4 stroke)

What gas/oil ration you using?

You say the saw idles good for long period of time. That is a really good thing. Seals are good and no vacuum/pressure leaks. You are gaining ground.

I was just saying that currently the saw is not quite to the rpm range at full throttle that I have been able to get it to in the past, even when cutting l, and I was just wondering how to get to that point. However I think you answered that question with your comment about the H adjustment. The tillotson carburetor "manual" that I got with this carburetor only says to adjust the screws (after the initial adjustment) until the desired rpms/performance is reached, so it wasn't too specific.

Yes I am still using the .404 chain, the previous owner was actually using 3/8" chain on the original .404 sprocket and ruined the sprocket. But I have some proper McCulloch bars meant for this saw now and .404 was the only type of chain that would fit on them, at least that I know of. I'm not to worried about cutting speed though, it's just that as I mentioned it seems like the saw has the potential to rev higher, but that shouldn't be too hard to get right.

Right now I'm doing 40:1 fuel to oil ratio, I think that is what's usually recommended.

Thanks for the help.

 

[Okie]

Play with the H jet but do not get it in CW to far or the saw will run lean. It's easy to get the H jet lean because to the ear the engine will sound smoother when really loaded in the cut and rev smoother out of the cut. The Tillotson initial jet setting is only for reference, adjust for the saws engine. If not familiar with the 4 stroke chainsaw sound you can listen to some video sounds on-line or
I adjust for the 4 stroke sound and the engine stop the sputtering 4 stroke when placed in a big load cut and just keeps on trucking, may even produce little bit of smoke.
I also do the load testing in big green wood with a log down instead of dead wood or standing wood. Just more user friendly for doing the adjust/test.

Keep a heads up and if the saws engine appears to be eventually (later on) starving for gas when in a heavy loaded cut for quite a while I've seen them gas tanks have a magnesium type powder or even a fine black/brown mold get through the in tank filter and start restricting the sintered iron filter in the Tillotson carb and the saw WILL STARVE FOR GAS. (and the in tank filter still look ok) I've seen the sintered iron filter look clean but when air pressure is blown backwards through the filter and it held in a WHITE paper towel the fine particles/mold or powder can be seen. The sintered iron filter is the finer one.
Also keep a heads up when removing the filter as to the direction of fuel flow so you can blow air in reverse for cleaning.
Usually when this is happening the gas tank has been left dry of mixed gas for very long period of time and the MAGNESIUM is shedding or the mold is growing. You can usually dump the gas and look with a flashlight at the condition of the tank and if bad I've had to give the tank a good tumbler cleaning with nut's/bolts/etc inside and then do not store the tank dry. Leave it oily during storage.

I've seen some of those tanks shed the powder and/or mold fast enough to clog the Tillotson sintered iron filter within one tank of gas. I'm not saying yours is bad I'm just giving you a hint that the sintered iron filter is really good and will start restricting full rpm gas flow and it still look ok to the eye when it starts clogging.

 

[camer_1107]

Play with the H jet but do not get it in CW to far or the saw will run lean. It's easy to get the H jet lean because to the ear the engine will sound smoother when really loaded in the cut and rev smoother out of the cut. The Tillotson initial jet setting is only for reference, adjust for the saws engine. If not familiar with the 4 stroke chainsaw sound you can listen to some video sounds on-line or
I adjust for the 4 stroke sound and the engine stop the sputtering 4 stroke when placed in a big load cut and just keeps on trucking, may even produce little bit of smoke.
I also do the load testing in big green wood with a log down instead of dead wood or standing wood. Just more user friendly for doing the adjust/test.

Keep a heads up and if the saws engine appears to be eventually (later on) starving for gas when in a heavy loaded cut for quite a while I've seen them gas tanks have a magnesium type powder or even a fine black/brown mold get through the in tank filter and start restricting the sintered iron filter in the Tillotson carb and the saw WILL STARVE FOR GAS. (and the in tank filter still look ok) I've seen the sintered iron filter look clean but when air pressure is blown backwards through the filter and it held in a WHITE paper towel the fine particles/mold or powder can be seen. The sintered iron filter is the finer one.
Also keep a heads up when removing the filter as to the direction of fuel flow so you can blow air in reverse for cleaning.
Usually when this is happening the gas tank has been left dry of mixed gas for very long period of time and the MAGNESIUM is shedding or the mold is growing. You can usually dump the gas and look with a flashlight at the condition of the tank and if bad I've had to give the tank a good tumbler cleaning with nut's/bolts/etc inside and then do not store the tank dry. Leave it oily during storage.

I've seen some of those tanks shed the powder and/or mold fast enough to clog the Tillotson sintered iron filter within one tank of gas. I'm not saying yours is bad I'm just giving you a hint that the sintered iron filter is really good and will start restricting full rpm gas flow and it still look ok to the eye when it starts clogging.

Thanks for all the great information
I hope to be able to finish tuning the saw sometime this week.

 

[camer_1107]

I just got the saw all tuned up thanks to Okie's advice, the thing runs like a tank now (in a good way).

Thanks for the help guys.