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Mcculloch 797, Super 797 thread

Lee H

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Since we already have a Mcculloch Kart thread and SP125 thread i thought it be best to start a Mcculloch 797 and Super 797 thread. If mods would like to change it be my guest since they are all 123cc saws.

The story goes, i bought this 797 along with many parts and a rebuilt short block from a fellow member
of this site. He was an ace to deal with.
I tore into the 797 and found a few issues that i knew about. Exhaust mounting holes were messed up
along with the decomp hole all wallowed out. I have a 797 block that was previously installed in a CP125
that i had already had bored to .040 so though it would be a good candidate for this stock build.
The 66251 number tells me it was originally in a 797 not a CP125 but the holes for a CP rear av mount and larger holes for rubber mount under fuel tank tells me it was in a CP125.
Will post as work progresses.


P1060618.JPG P1060622.JPG P1060623.JPG
 

Lee H

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The block i chose to use was previously bored to .030 but needed to go another 10 to clean it up.
I am also using a 101 Kart motor piston and rod with 1/2 inch wrist pin.
 

Bigmac

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Since we already have a Mcculloch Kart thread and SP125 thread i thought it be best to start a Mcculloch 797 and Super 797 thread. If mods would like to change it be my guest since they are all 123cc saws.

The story goes, i bought this 797 along with many parts and a rebuilt short block from a fellow member
of this site. He was an ace to deal with.
I tore into the 797 and found a few issues that i knew about. Exhaust mounting holes were messed up
along with the decomp hole all wallowed out. I have a 797 block that was previously installed in a CP125
that i had already had bored to .040 so though it would be a good candidate for this stock build.
The 66251 number tells me it was originally in a 797 not a CP125 but the holes for a CP rear av mount and larger holes for rubber mount under fuel tank tells me it was in a CP125.
Will post as work progresses.


View attachment 251918 View attachment 251919 View attachment 251920
Cool, going to be a fun build. Do you mind taking more pics of that block from the coil side? I am always curious about these oddball blocks! Must have been a transition block
 

Lee H

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I don't believe this is a transition block. It has the boost port cover which was gone on the late Super 797's.
It's not a very early 797 as the relief in the big hole for crank removal is at the 2 o'clock position, not the 12
o'clock. The 66251 number was also gone on later Supers.

P1060625.JPG P1060626.JPG
 

Bigmac

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I don't believe this is a transition block. It has the boost port cover which was gone on the late Super 797's.
It's not a very early 797 as the relief in the big hole for crank removal is at the 2 o'clock position, not the 12
o'clock. The 66251 number was also gone on later Supers.

View attachment 251956 View attachment 251957
With cp and 797 super production happen at the same time frame, that block must be a late 797, non super but made when the cp was just being introduced, cool block
 

Lee H

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With cp and 797 super production happen at the same time frame, that block must be a late 797, non super but made when the cp was just being introduced, cool block

I actually think the block was converted to a cp block sometime in its life. The cylinder fin i believe was drilled and tapped
to accommodate the rear av mound. I don't think it's factory as it won't fit right with the little rib on the fin.
 

Bigmac

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I actually think the block was converted to a cp block sometime in its life. The cylinder fin i believe was drilled and tapped
to accommodate the rear av mound. I don't think it's factory as it won't fit right with the little rib on the fin.
Ok, so it doesn’t have the cast av boss?
 

jacob j.

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I actually think the block was converted to a cp block sometime in its life. The cylinder fin i believe was drilled and tapped
to accommodate the rear av mound. I don't think it's factory as it won't fit right with the little rib on the fin.

I've seen that before - I rebuilt a CP years ago for an old-time wood worker that had a 797 block instead. He loved the saw and had bought it in 1976 from the original owner.
I didn't know if the original owner had done it or if it was a dealer conversion of some sort. Saw-King bored the block for me and I went with a .020" over piston. The wood
worker had worn out probably six or seven 32" bars on that saw over the years. He was mainly working with Myrtlewood.
 

Bigmac

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Here is a pic of the mounting place for the AV mount.


View attachment 252017
Thanks, ya looks like it’s definitely a 797 block, I have a cp block that is similar looking to it but it has the cast Av boss and The recessed exhaust gasket, and the recessed but plugged boost port. It’s cool to see the evolution of these blocks.
 

Lee H

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Trying to decide what to do about a carb, Use the original flatback with a nos primer i have
or convert to a Tilly HL103 which i think i have as they were used on the early Super 797's.

What you all think i should use?
 

Bigmac

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Trying to decide what to do about a carb, Use the original flatback with a nos primer i have
or convert to a Tilly HL103 which i think i have as they were used on the early Super 797's.

What you all think i should use?
That’s a tough call, never had a working flat back primer so I have no experience there! LOL have heard if the primer works good there nice carbs. But the Tilly’s work great and are easy to tune, Going to be a winner either way
 
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