Mcculloch 797, Super 797 thread

[Bigmac]

Here is some pictures of the P/C. After a weekend of looking the IPL's of the early 797, S797, CP125, and 101 kart engines, I want to verify that I'm reading them correctly. It appears the simplest solution would be to find the proper oversize piston and put it back to stock. My question is for you all that have ran 123cc saws. Would it be worth milling out the boost ports, finding a windowed piston with corresponding rod, wristpin and boost cover? Is that all that would be needed to make it like a regular 797? Jeff View attachment 472786View attachment 472788View attachment 472789

It definitely doesn’t hurt, it’s not a massive gain. I had terry do it to a cp block, but did a lot of other work to it so it wasn’t the only mod.

 

[heimannm]

I have 69241 (+0.010") and 69242 (+0.020") piston assemblies that are used with the 69408 (1/2") wrist pin. That's my only contribution...Nate would know a lot more about performance enhancers.

Mark

 

[Lee H]

Welcome to the forum. Lots of info here and very knowledgeable folks here.

I may have a new std piston, But before you put a std piston back in i would mic the bore and make sure it is round. I bet it isn't anymore and in that case boring the cylinder to the next over size would be recommended. I will also look to see what i have in over size pistons.

Lee

 

[B Royals]

Bigmac - thanks for the info, I talked to Terry today about having some machine work done.

Mark - Thanks for looking, those two could be an option depending on how the cylinder turns out. Are those window pistons by chance?

Lee H. - Thanks for the welcome. I believe the cylinder is in need of boring due to the piston damage. I'm not kidding you that I have read over 200 pages this past weekend. I probably ought not have read the SP125/101 threads lol. You have some very nice builds. I read a lot of your and JJ's threads, very cool and helpful.

I'm thinking I want to open the boost port window, and find a regular 797 or kart window piston. I'm digging through IPL's trying to make sense of the 101 variation pistons. Terry did say that you could drill two holes in a S797/CP125 piston for the same effect though. Does anyone have a boost port cover they might would part with?

Jeff

 

[jacob j.]

Does anyone have a boost port cover they might would part with?

Jeff

Hey Jeff -

Welcome! Chuck (Strockerace) has boost port covers here: https://www.ebay.com/itm/267418117346

I've bought a lot of stuff from him over the years and have had good luck. Terry is the ace when it comes to
McCulloch, so he won't steer you wrong. Your existing piston is likely the 1/2" wrist pin so you may be able to
re-use your connecting rod.

 

[B Royals]

Hey Jeff -

Welcome! Chuck (Strockerace) has boost port covers here: https://www.ebay.com/itm/267418117346

I've bought a lot of stuff from him over the years and have had good luck. Terry is the ace when it comes to
McCulloch, so he won't steer you wrong. Your existing piston is likely the 1/2" wrist pin so you may be able to
re-use your connecting rod.

Thank you Jacob. My wrist pin is 1/2" with the bearings in the piston. I was just reading some of your posts comparing the different pistons and rods. Am I right in thinking my Super 797 shares a lot of parts with the 101A? (Connecting rod, small end bearings, wristpin, crankshaft) I actually have a few pistons on my watch list from Chuck. I think piston P/N 84470 (.010 over) would work in my saw, if I'm interpreting the IPL's correctly. Or should I just tell Terry what I want, and roll with it.

 

[B Royals]

It definitely doesn’t hurt, it’s not a massive gain. I had terry do it to a cp block, but did a lot of other work to it so it wasn’t the only mod.

Was this the CP block where you epoxied the intake and transfers, ported the intake manifold with the 5 degree flywheel?

 

[Bigmac]

Was this the CP block where you epoxied the intake and transfers, ported the intake manifold with the 5 degree flywheel?

The cp we added the boost port, I lifted the exhaust port, and did some minor blending. Added the modded 795 stuffer and 5° flywheel, and it had the custom intake with v4 reeds and wb37 carb.

 

[Bigmac]

This is the cp

 

[Bigmac]

This one with the 32” bar