Is this Super 250 too far gone

[Dan_IN_MN]

Brian,

Keep your eye on the mail box...I tested it on my 200 and it seemed to work just fine. No doubt you will have to do a little fine tuning to get the L and H setting just right for your Super 250.

Mark

Mark

Good going helping out! AGAIN!

 

[blsnelling]

Brian,

Keep your eye on the mail box...I tested it on my 200 and it seemed to work just fine. No doubt you will have to do a little fine tuning to get the L and H setting just right for your Super 250.

Mark

Way to go Mark!

 

[Brian13]

Brian,

Keep your eye on the mail box...I tested it on my 200 and it seemed to work just fine. No doubt you will have to do a little fine tuning to get the L and H setting just right for your Super 250.

Mark

Thank you Mark, I will be on the look out. Still have not been able to get out in the garage to fix the paint. Wife hasnt been feeling well and I have been taking care of the kids. Hoping to get started this weekend.

 

[warjohn]

Great job so far Brian. I have finally had time to catch up on thus thread. Bigjohnstin and I have 4 old Macs which include a 250 and a 200. We plan on doing a father son restoration project on them this winter. This thread has peaked our interest in getting a couple of them done.

 

[heimannm]

Brian, after all you have been through, did you check the duckbill valve in the cap to the fuel tank? They are supposed to vent atmospheric pressure into the tank and hold a little pressure once the saw warms up, but if they are a solid glob of goo they hold too much pressure in the tank once the saw warms up and forces fuel past the needle & seat. Sorry not to mention this sooner as it was the topic of another thread by Gasoline71 not so long ago.

May be one more arrow in your quiver as you get the S 250 sorted out.

Mark

 

[Eccentric]

Brian, after all you have been through, did you check the duckbill valve in the cap to the fuel tank? They are supposed to vent atmospheric pressure into the tank and hold a little pressure once the saw warms up, but if they are a solid glob of goo they hold too much pressure in the tank once the saw warms up and forces fuel past the needle & seat. Sorry not to mention this sooner as it was the topic of another thread by Gasoline71 not so long ago.

May be one more arrow in your quiver as you get the S 250 sorted out.

Mark

Hey Mark................are those duckbill cap check valves available still? I need one for my Mac 77...

 

[heimannm]

The duckbill valve for the fuel cap on the later model large McCulloch saws 53766 are still available, I normally get them from Bob Johnson for $6 each.

I don't know about the really large valve used in the older saws like your 77 (47252) as I have not had to replace any of those yet. I do have a few older model saws with that style and they seem to hold up much better than the later ones.

Check with Bob Johnson (607 638 9297) as he is the most likely source, if he doesn't have them he may know someone that does.

I have a variety of older fuel caps, some simply have a small hole drilled with a cotter key in it, some have a small steel or felt washer under the cotter key inside the cap, some are completely solid as best I can determine. I don't think I have any with the rubber valve but I will try to remember and look around when I am home again next week.

I could make an interesting thread (to old McCulloch fans anyway) at the shear number of different styles of fuel caps McCulloch supplied, all with the same thread size so any saw from the 3-25 through the SP125 could share a common cap.

Mark

 

[Brian13]

I did check the tank cap. It does not have the valve, but a porous center. It is definitely not plugged. It looked like there might have been some sort of rubber grommet on the inside of the cap that was deteriorated and gone. So if anything it shouldnt be able to build much if any pressure at all. After I saw Gary talking about the same problem I was having that was the first thing I checked. The only thing that makes sense to me at the moment is the seat being bad. There could be other issues that I dont know about. All the fuel damaged parts are repainted and ready to be put together. I hope this is the last time I rebuild this saw.

 

[Eccentric]

The duckbill valve for the fuel cap on the later model large McCulloch saws 53766 are still available, I normally get them from Bob Johnson for $6 each.

I don't know about the really large valve used in the older saws like your 77 (47252) as I have not had to replace any of those yet. I do have a few older model saws with that style and they seem to hold up much better than the later ones.

Check with Bob Johnson (607 638 9297) as he is the most likely source, if he doesn't have them he may know someone that does.

I have a variety of older fuel caps, some simply have a small hole drilled with a cotter key in it, some have a small steel or felt washer under the cotter key inside the cap, some are completely solid as best I can determine. I don't think I have any with the rubber valve but I will try to remember and look around when I am home again next week.

I could make an interesting thread (to old McCulloch fans anyway) at the shear number of different styles of fuel caps McCulloch supplied, all with the same thread size so any saw from the 3-25 through the SP125 could share a common cap.

Mark

Thanks Mark. I'll check with Bob. My 77 cap has a large hole in the center (about 1/8") and a 1/4"-ish diameter, 1/2"-ish long tubular extension cast into the inside of it. The IPL shows the #47252 valve as fitting onto or into that extension...


So all the large Macs use the same thread size cap then? That'd mean I could use a later style cap (with a new check valve) to run the saw if I can't find a check valve for the 'stock' cap..................and save the 'stock' cap for 'looks' during shelf duty. That's a relief.

 

[Brian13]

Another thing I had noticed was, every time you pulled the cord it would dump fuel out of the throat. The last time I never even got it to start. It just flooded the airbox right away.

 

[Eccentric]

Another thing I had noticed was, every time you pulled the cord it would dump fuel out of the throat. The last time I never even got it to start. It just flooded the airbox right away.

To me, that sounds like the pump section of the carb is working quite well.............and that the needle/seat aren't closing completely. Maybe yet more crap holding the needle off the seat. Another option is of course that the fuel is being pumped into the carb, then leaking past somewhere where there shouldn't be any flow. Welch plug, metering diaphragm, etc. Just peeing in the wind here...

 

[Brian13]

To me, that sounds like the pump section of the carb is working quite well.............and that the needle/seat aren't closing completely. Maybe yet more crap holding the needle off the seat. Another option is of course that the fuel is being pumped into the carb, then leaking past somewhere where there shouldn't be any flow. Welch plug, metering diaphragm, etc. Just peeing in the wind here...

I am not going to say its impossible there is still garage in the seat, but it got almost a whole can of carburetor cleaner through it. Welch plug or diaphragm could be my issue though.

 

[heimannm]

Brian,

There is suppose to be a duck bill type check valve under that sintered metal vent cover. It is possible the remnents of yours is still under there plugging it up. Did the saw leak fuel out through that vent when it was running? If not, I would go ahead and gently punch it out from the inside of the cap and order the new duck bill valve from Bob. In fact, you will want to install the new valve in any case or the saw will spit fuel out the vent every time it runs.

Have a look at the IPL and you will see what I mean.

And be prepared, the black goo that is the remains of the original duck bill will stick like tar to everything and can be quite difficult to clean off.

Mark

 

[Brian13]

I have a picture of what gas will do to paint when the paint is submerged in gas. And I have more pics of the repair. Feels like I am rebuilding it all over again.

I finished cleaning up the handle bar and put a rubberized paint on it. I was hoping for a smoother finish but non slip is ok too.

 

[Brian13]

Mark I was looking at the IPL on the gas cap and the duckbill is gone completely. Here are some photos, the first two are the cap I have been using. The third is another I have, the top is the same at the other but the underside is a little bit different. On the cap I have been using if you tilt the saw over to far it will leak out, so I dont think it is building up too much pressure. Might be causing another problem though.

.

 

[cbfarmall]

You know, for these cap vents, and this cap is very common on the 70s Macs, I stole an idea from Stihl. Instead of fooling with a duckbill valve, I stuffed a short pic of fuel line in the hole and then screwed in a set screw. This is more or less what Stihl did with alot of it's older saws for the tank vent--08S, 070/090, 028, 038, etc.. I've run the 550 since about 10 or 15 minutes, and so far so good. Some experimenting can be done with the size of the screw so you don't actually plug up the vent hole.

I'll get a picture of it if you want.

Chris B.

 

[Brian13]

You know, for these cap vents, and this cap is very common on the 70s Macs, I stole an idea from Stihl. Instead of fooling with a duckbill valve, I stuffed a short pic of fuel line in the hole and then screwed in a set screw. This is more or less what Stihl did with alot of it's older saws for the tank vent--08S, 070/090, 028, 038, etc.. I've run the 550 since about 10 or 15 minutes, and so far so good. Some experimenting can be done with the size of the screw so you don't actually plug up the vent hole.

I'll get a picture of it if you want.

Chris B.

If you have a pic that would be great. I think I know what you are saying but a pic would give me a better idea.

 

[Brian13]

Ok I think I am done, again. Put everything back together, and now going to let it sit for another day or two to let the paint fully cure. Could someone look at the way throttle is hooked up to the carb. No matter how I try to hook it up something doesnt seem right.

 

[leeha]

Brian, I think it looks ok. On that type
of carb the throttle rod closes the throttle.
it doesn't open it. When the rod moves forward
the intake suction opens the throttle plate.


Lee

 

[cbfarmall]

Here's 2 pictures of a fuel tank vent.

The first is an 08S Stihl. Look past the shroud and you'll see the fuel hose on a barb with a set screw at the top. That's Stihl's vent and it works pretty well.

The second is how I adapted it to a Mac fuel cap.

Chris B.

Brian, since it should be fresh in your mind, I have 2 questions about your Super 250 piston. Are there locating pins for the piston rings? From the IPL, it looks as if one ring gap is at the exhaust port and one is opposite--is this the case with yours? Thanks.