McCulloch 797

A few days back... this 797 showed up... it's a tad on the rough side... but it has tons of compression, and needs a good cleaning. It sat in a barn for 25 years... So the bar oil and crud is almost like it crystalized on the outside of the saw.

So I use some stuff made by POR-15 called Marine Clean... works great, and is water soluable. Won't mess up paint either. I cleaned up the recoil with it... it was almost black with crud... now the yellow really comes through. It's a lot cleaner than the rest of the saw.

It will be a (another) winter project...

36" bar and .404 chain. Oiler needs some work, and the carb prolly needs to be gone through.. I made some cuts with it... so it did okay considering I haven't touched the carb or adjusted the oiler. Chain got a little hot, so I had to stop cuttin'... not enough oil... but I can really feel the torque from the 123cc's.

So here is a vid of me makin' a couple of cuts... Like said above, oiler not workin' too good, so the chain was a little hot.

Anyways... made one cut with the saw and then cut noodles. The .404 chain was really tossin' chips. But by the time the noodles were gettin' cut, the chain was gettin' a little tight from the heat. So I quit.

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Love the sound of a big cc (123cc's) McCulloch.

Gary

That old beast sounds real good, Gary.

I'm loving the chain break!

Brake is the thing that stops it.
Break is what happens when it quits working.

Ya done filled it plumb full of noodles .

Sounds okay just needs a tad bit of tweeking .It will do a better after you get the cobwebs blown out of it .

Some of the old timers say a 797 was a better go getter than an SP 125 .Can't say myself,never ran a 797 only the 125 .

Oooops!

Nice Gary.

The only saw I own with a chain brake is my Stihl 044... All the oldies didn't come with them.

Gary

Brakes were an option on the left hand start models like the 125 although I doubt many ordered them that way .I've never seen any type brake on a right hand start Mac .

Can this one be made to run like a hot saw Al? Like the 125's?

Not that I'm gonna... just thinkin' out loud.

Gary

It's basically the same engine Gary .The exception being the 797 used the same design piston with the bearings in the piston,like a 101 kart engine whereas the Sp 125's had the bearing in the rod .

The real early 797's had a full skirt piston with thick rings and the later ones used a seml sliper type piston with thin rings . Rather I assume the later used thin rings like the SP 125's . I could look it but I doubt it makes much diff .

I don't know about the comp ratio .The Sp 125 was 7.5 to one .If you can pull that thing over without the use of a decomp I would say it is less than that .

No matter ,running real good that thing will toss chips to a fair thee well at around 9- 10,000 rpms more or less . I'll look it up later on to see what the difference in specs might be .

Al Smith said:

I don't know about the comp ratio .The Sp 125 was 7.5 to one .If you can pull that thing over without the use of a decomp I would say it is less than that .

Click to expand...

I can do it... but holy shit, it's hard. I just wanted to see if i could do it. If that thing didn't have a decomp, I don't know how anybody would be able to start it.

Gary

My big Jonsered 2095? doesn't have a decomp. It's fun to watch a new guy try to start it.

PLEASE get a video of that Brett!

Here is what I found .The 797 is 6 to one comp ratio but I magine it's about like pulling over 10 to 1 .

The early 797's used a Walbro flat back .The later ones ,797 S used either a Tilley HL or a Tilley HS or a Walbro SDC I think . The ignition was large coiled like about all the reed valvers .

This was superceeded by The CP 125 1n 1972 which also used the large coil .This engine is more closely related to the kart engine than any other .Tilley HL or Walbro SDC .

I believe it was 1977 that this model was superceeded by the SP 125 and Sp 125 C .This only used the Walbro SDC or in some cases the Tilley HS as they were interchangeable . Comp was not listed on the CP and SP models but I'm pretty sure they are 7.5 to one .The kart engine were 9.5 to one in stock form but seldom remained that way for long . The SP 125 used the same ignition as the 10 series saws .

I think they only made the SP models a few years which would pretty much coincided with the halt of the old growth cutting in the PNW .

Now keep in mind that thing is a Mac and most likely a PNW old growth saw .Anything could have been done to the innards as many parts were interchangable .

No matter what it is it's a keeper and likely to run for the next 50 years .Pretty tough to kill one of those old plow horses .

Thanks a ton for that info Al... the saw came from Oregon, and it has a Tilly HL for what I can tell... The 640 I got from Brian has a flatback in it.

The 640 weighs as much without the bar and chain as the 797 does with the 36" bar on it.

...and the 797 has 43 more cc's!

Gary

My poor 640 is gonna end up at the bottom of the pile under Gary's work bench.

Nope... it's sittin' righ next to the 797. Pulled the carb out. I'm on the hunt for a rebuild kit. Might have to do as Al suggested and soak the diaphram in brake fuid, and make my own gaskets.

It runs great... just fills the air filer/ carb housing with fuel...

Gary

It's a keeper too .Not to worry he most likely will have the only running one for miles around once he gets it tweeked in .

I'm not sure if that flat back takes the same diaphragm as the big old monster BCD 's they used on karts or not .Those kits are 50 a pop .

I'll go on search .

Thanks Al... I'm comin' up empty. I'm gonna post the question on Magnus' site as well... Lots of saw nuts there that have access to a lot of old Mac and Homelite parts.

Gary

Might not be a bad idea .

If that diaphragm is good as it must be else it wouldn't run ,the gaskets would not be that hard to make .

Oh,aha while I'm thinking about it,there is a little gasket betwwen that stupid little prim pump that leaked like a sieve on the infernal flat back on my 250 .That one is easy to make .If it isn't any more than that you're in like Flynn .

That might be all it is... I'm gonna tear that apart soon... plus the stupid fuel inlet at the bottom of the carb is bigger than the outlet from the fuel tank pickup. I hate when manufacturers do that. So it requires a special fuel line to do the job.

Or do like I do and stick a smaller diameter piece of fuel line inside a larger diameter fuel line about a 1/2" and heat it with a little butane torch. Melts it together. But ya gotta be careful not to melt it too much. It only works with the clear yellow stuff... not sure what it's called. Excelon I think.

Gary

Tygon is the name of one synthetic type of fuel line .Might have the wrong spelling on that .I imagine Mac might have had a special molded fuel line on that saw,they did on many. Fact is many saw makers did .

I do about like you and stuff one inside the other and it works . They all try as best they can but it's nearly impossible to out fox Yankee ingenuity .

I just thought of something and felt it noteworthy to post . On those two old work horse Macs I doubt you need any parts but if you do,there are several possible sources I can think of .

Fayettville eqt repair ,in Fayetteville NY .They also have a website .

Bob's lawn mower repair service in Maryland NY . Considated Equipment in Burnby BC right in Paulys' back yard . This Is Mike Acres .Probabley if you need a Mac part from them it would be best to talk directly to Mike .

Another could be Rich Dougan alias "saw king" in Myrtle Creek Oregon .

I've dealt with all these people and they are all good .

There are a couple on a site I know longer visit but those you will have to sort out on your own .