McCulloch Chain Saws

[ChipsFlyin]

I think just about everybody on here likes to watch a chainsaw vid.

I knew after the first cut that it was running lean but really found out going into the second. Super 797

 

[Walter Glover]

Cp70 SDC carb is flooding. Tore apart and the Welch plugs appear to have sealant on them. Could this be the source of my flooding? Seal-all work here?
Might have been a slight burr on needle as well?
On the Welch plugs, I can close off both needles to stop the flooding and clear the saw, jets just cracked to make it run, low say 1/2 or less and hi just starting to open.
Thoughts anyone?
Cheers

 

[fossil]

Cp70 SDC carb is flooding. Tore apart and the Welch plugs appear to have sealant on them. Could this be the source of my flooding? Seal-all work here?
Might have been a slight burr on needle as well?
On the Welch plugs, I can close off both needles to stop the flooding and clear the saw, jets just cracked to make it run, low say 1/2 or less and hi just starting to open.
Thoughts anyone?
Cheers

Stuck metering needle would be a good bet. What level do you have the metering lever at? Even if it's a bit too high it will flood.

See attached manual

 

[Walter Glover]

Thanks Tim
Will try again with metering clean
It was flush to carb body height

Edit:
Must have been some grit holding the needle open. Starts and runs normal with basically one turn on each screw.
Cleanliness is next to Godliness for sure......
Walter

 

[heimannm]

Always pressure check a carburetor to verify that the metering needle is seating properly, it will save a lot of grief.

Mark

 

[Walter Glover]

Yes indeed! I have no excuse there have the equipment to do it (instrument mechanic by trade)
Will check from now on. The old 1-52 is leaking fuel into carb box but just realized that might be the needle pivot screw. If just the needle it would be going into the engine. Hmmmmmm

 

[Mac&Homelite]

Yes indeed! I have no excuse there have the equipment to do it (instrument mechanic by trade)
Will check from now on. The old 1-52 is leaking fuel into carb box but just realized that might be the needle pivot screw. If just the needle it would be going into the engine. Hmmmmmm

Same problem with my 250 that when it is running it spits a ton of fuel out of the carb, so it's a needle issue. What kind of pressure are we looking for to test it with? Something in the neighborhood of 7psi?

 

[Walter Glover]

Test pressure, now that is a good question. Have read 12 psi to pop the needle but tried that on a tilly HL and was over 20 near as I can measure.
Need to find that out eh.

 

[ChipsFlyin]

Cp70 SDC carb is flooding. Tore apart and the Welch plugs appear to have sealant on them. Could this be the source of my flooding? Seal-all work here?
Might have been a slight burr on needle as well?
On the Welch plugs, I can close off both needles to stop the flooding and clear the saw, jets just cracked to make it run, low say 1/2 or less and hi just starting to open.
Thoughts anyone?
Cheers

The sealer on the welsh has me thinking. I had a welsh that did not seal about 6 months ago resulting in flooding and fuel coming out of the carb. When I rebuild the SDC on the 797 I made sure that I had the correct size set punch to make sure both of the welsh plugs sealed. I use old drill bits that were just larger than the correct diameter and tuned them up on a small grinder to make sure the ends were flat and they fit just inside the seat. A welsh should not need sealer. If you decide to rebuild the carb be very careful when drilling the welsh plugs not to go too deep and hit the internals. The price on the OEM kits are pretty good.

https://www.ebay.com/sch/i.html?_nkw=walbro+sdc+carburetor+kit

 

[ChipsFlyin]

Stuck metering needle would be a good bet. What level do you have the metering lever at? Even if it's a bit too high it will flood.

See attached manual

To add on to the metering. Like Fossil said make sure that the lever is set correctly and the needle seats fully. There is the other side also when adjusting the lever. I found with trial, error, opening up carbs that were messed with or in the beginning me setting wrong -- sometimes the metering lever appears to be set correctly on the carb floor but was not moving the needle or not through the entire open close motion due to the fork being pushed down. What works the best for me is while setting the lever to the required spec on the carb floor is having the little tab that slides on the needle to be just touching the the upper part of the needle slot WHILE the needle remains seated. I don't like any play - pushing down on the lever will immediately moved the needle. That way I have no question that there is a functioning closed and open circuit with no delay on opening.

 

[Mac&Homelite]

That is a good idea as well, as I have been messing with the HL carb for quite some time on just the lever height. Not having it make contact the full distance would obviously change how the carb behaves. Going to try to do that with the carb this weekend if I get some time.

 

[ChipsFlyin]

That is a good idea as well, as I have been messing with the HL carb for quite some time on just the lever height. Not having it make contact the full distance would obviously change how the carb behaves. Going to try to do that with the carb this weekend if I get some time.

If I can remember HL's are set flush with the floor.

 

[Mac&Homelite]

If I can remember HL's are set flush with the floor.

Yes, that is correct as per instructions.

 

[Brian Thacker]

On that 7-10, if you go 30 over, do you have to mess with the jetting?

Usually you just have to readjust the carb. It may need to be a little richer on the high side.

Brian

 

[raumati01]

Just scored a 7-10 , 10-10a and 1-51 ..... and 5 mini macs for $120. The mini macs will be finding a new home asap. What's the difference between the super 250 I have and an I -51 ?

 

[Walter Glover]

Great score! I dont think there is any difference from 250 to 1-51
Same 80cc saws iirc.
Enjoy and share some pics!

 

[Mac&Homelite]

1-51 is an 80cc while the super 250 is 89cc. Good saws, but heavy and sort of slow. Gobs of torque though. You will definitely like the 7-10 though, that will be a treat to run.

 

[mad murdock]

I have a 10-10 question for you guys deep into these wonderful saws. I have a later model short clutch cover with chain brakes model pro Mac 10-10. It is in real good shape, on a compression test pulled 175 psi in about 4 pulls. I put a K10SDC kit in the carb, as it ran, but was rich and wouldn’t go past fast idle because running way rich and spitting gas. I read through an “026 spitting gas” thread, I haven’t leak checked the carb yet, will do that next. Any other suggestions? I will check the auto Oiler check valve next as the carb kit did not solve the issue.

 

[fossil]

I have a 10-10 question for you guys deep into these wonderful saws. I have a later model short clutch cover with chain brakes model pro Mac 10-10. It is in real good shape, on a compression test pulled 175 psi in about 4 pulls. I put a K10SDC kit in the carb, as it ran, but was rich and wouldn’t go past fast idle because running way rich and spitting gas. I read through an “026 spitting gas” thread, I haven’t leak checked the carb yet, will do that next. Any other suggestions? I will check the auto Oiler check valve next as the carb kit did not solve the issue.

The first thing I would check is that the carb diaphragms and gaskets are in the correct order and then make sure the metering lever is set correctly and then pressure check the carb.

There is a Walbro manual for the SDC carb posted in the link below. That should help sort out whether or not you have a carb issue.

http://www.arboristsite.com/community/threads/mcculloch-chain-saws.71126/page-1350#post-6363907

 

[Walter Glover]

Tim, is there a pressure test procedure somewhere?
TIA