McCulloch Chain Saws

[2broke2ride]

Iv'e seen that done to old snowmobile pistons, here's another take on that concept this piston was in a 1969/70 race motor.
Nice group of yellow you have there Jethro/like the antivibe fixView attachment 798788

They called that "golfballing" for obvious reasons. The examples I've seen are far more extreme than that. It lightened the piston and supposedly lowered skirt friction. Who knows really? Old racing tech. Lol

 

[kbeck]

They called that "golfballing" for obvious reasons. The examples I've seen are far more extreme than that. It lightened the piston and supposedly lowered skirt friction. Who knows really? Old racing tech. Lol

Right a forgot what they called it but I sold the motor this was in and the ones that were installed were 10 fold compared to this

 

[PogoInTheWoods]

And here she is with her new friends

Looks good and right at home..., maybe even a little spoiled already. LOL Again, congratulations. And nice job on the a/v, too.

 

[vinnywv]

Heres the newest mac to the fleet: the sp70, cleaned up with new chain, roller nose bar and cold weather handle grip. Runs and cuts great. Weighs 19.5 lbs. As it sits.

 

[Jethro 2t sniffer]

Heres the newest mac to the fleet: the sp70, cleaned up with new chain, roller nose bar and cold weather handle grip. Runs and cuts great. Weighs 19.5 lbs. As it sits. View attachment 798826 View attachment 798827 View attachment 798828

That's nice man really nice love the bar.

Did you chip off the last of the paint on the starter? I have 1 that looks dam neer identical the paint was just falling off so thought bugger it I'll make it shiny.

Yours has a falling sight on it that's cool didn't realize they had the sight and the logo thought the sight was only on the later plain ones.

Looks good and right at home..., maybe even a little spoiled already. LOL Again, congratulations. And nice job on the a/v, too.

Thanks Poge yes I'm spoiling it rotten lol

Strange having a new "best" saw in the mix the 800 held the trophy for a long time now it's sorta cast to the side a little.

The AV fix was a fiddly little job I've got some thick rubber somewhere instead of the four thin bits it will look a bit nicer but this is fine until then. I made them the total height of the gap between tanks so they can't turn around. Can also tighten or loosen the screws for a bit of tuning. Actually quite cool thinking about that.. aftermarket adjustable AV mount for long bars hahaha anyone want some?

 

[Goinwheelin]

@Jethro 2t sniffer check out some of the DIY polyurethane bushing videos on YouTube. I was looking at those when I tore apart that 5200 trying to find an affordable alternative to $34 ea.
Oh and good lookin saw!

 

[Jethro 2t sniffer]

@Jethro 2t sniffer check out some of the DIY polyurethane bushing videos on YouTube. I was looking at those when I tore apart that 5200 trying to find an affordable alternative to $34 ea.
Oh and good lookin saw!

That would be the ticket absolutely. Ron mentioned that as well. Where the heck do ya buy that kind if stuff though?

It could be done though I'd make a mold that screwed down the metal parts in the right place "box" it up and go

 

[Jethro 2t sniffer]

Heres the newest mac to the fleet: the sp70, cleaned up with new chain, roller nose bar and cold weather handle grip. Runs and cuts great. Weighs 19.5 lbs. As it sits. View attachment 798826 View attachment 798827 View attachment 798828

Dam that's a nice saw. I keep looking at it. The best muffler cover the best clutch cover the sp saws with out the big boot strap mmmmm its really very nice and the cherry on top of new insides

 

[vinnywv]

That's nice man really nice love the bar.

Did you chip off the last of the paint on the starter? I have 1 that looks dam neer identical the paint was just falling off so thought bugger it I'll make it shiny.

Yours has a falling sight on it that's cool didn't realize they had the sight and the logo thought the sight was only on the later plain ones.



Thanks Poge yes I'm spoiling it rotten lol

Strange having a new "best" saw in the mix the 800 held the trophy for a long time now it's sorta cast to the side a little.

The AV fix was a fiddly little job I've got some thick rubber somewhere instead of the four thin bits it will look a bit nicer but this is fine until then. I made them the total height of the gap between tanks so they can't turn around. Can also tighten or loosen the screws for a bit of tuning. Actually quite cool thinking about that.. aftermarket adjustable AV mount for long bars hahaha anyone want some?

There was no paint on it. All i did was clean the grime with a scotchbrite pad. Thanks for the comments, the bar is a 22" partner bar. I filed the holes out a tad. Pretty cool. Ive got another one on my pm700 that still reads partner on it. Theres a guy on ebay selling them. Pretty reasonable too.

 

[Goinwheelin]

They use polyurethane roof and lap sealant you can buy it at the hardware store in a tube for your caulking gun.

https://www.homedepot.com/p/Loctite...e-Roof-and-Flashing-Sealant-1675273/203163733

 

[Jethro 2t sniffer]

There was no paint on it. All i did was clean the grime with a scotchbrite pad. Thanks for the comments, the bar is a 22" partner bar. I filed the holes out a tad. Pretty cool. Ive got another one on my pm700 that still reads partner on it. Theres a guy on ebay selling them. Pretty reasonable too.

That's a very nice bar. No wonder I was wondering at the length like hmmm its bigger than a 20 but but not sure it's a 24 hmm must be a 24 lol.

They use polyurethane roof and lap sealant you can buy it at the hardware store in a tube for your caulking gun.

https://www.homedepot.com/p/Loctite...e-Roof-and-Flashing-Sealant-1675273/203163733

Well that just opened up a can of worms lol I'm realizing now we got a similar thing at work its black "windscreen" sealant and we use it gluing a plastic "thingy" to concrete it gets kicked and stood on by cows all day.

Are the rears the same?

 

[PogoInTheWoods]

Show off day! Nice, fellas.

So I'm crunching IPLs again trying to determine whether I need an 85240 or a 69412 for this 3 finger transfer iron bore cylinder on the 7-10. Still finding more confusing info and differences among the various applications I've been able to find for both pistons -- including different wrist pin, bearing, connecting rod, and of course, ring numbers.

Gonna give Bob a ring after his nap and see what he has to say. Have a few more numbers to cross-ref first. Wish it was easier to identify the cylinders in relation to their pistons instead of them seemingly being numbered for all the various exterior fastening points / features instead. Makes it nearly impossible to match pistons and cylinders, especially for the 70cc series considering all the variations between just the p / c combinations alone..., not to mention the ambiguity (and downright inaccuracy in some cases) inherent in the available documentation.

And Vinny, any chance you could measure pin to crown and pin to skirt on those pistons? Kinda curious about those numbers, too.

 

[Goinwheelin]

Jethro I would have to look at the rear mounts when I get home as I am not sure. I’ll see if I have a picture though and get back to you.

 

[Goinwheelin]

Not the best angle but you might be able to zoom in.

 

[2broke2ride]

What is the proper champion plug number for the 5-10 (or any of the 10 series for that matter)? you'd think I'd know by now lol

 

[PogoInTheWoods]

I just happen to have a 5-10 IPL open. LOL

Looks like AC may have ruled the day it was printed.

 

[Jethro 2t sniffer]

Not the best angle but you might be able to zoom in. View attachment 798834

Cheers man they look the same to me

I just happen to have a 5-10 IPL open. LOL

Looks like AC may have ruled the day it was printed.

View attachment 798844

Poge you must be rolling all these numbers round in your sleep lol

 

[PogoInTheWoods]

It's worse than you think. Trust me. LOL

So I just ordered what appears to be Bob's last 69412 piston for the 7-10. Seems as though there's been a run on those and the 85240 lately. LOL Ordered the 85241 rings and a 65389 pin as well since everything points to the 69030 / 85239 piston using a different pin. My guess without measuring would be that it's just slightly shorter for the bosses in the windowed style piston. He has a shelf full of the later 85240's (which are essentially the same piston with slightly different skirt dimensions) that supersedes the 69412 if anyone was worried about availability. I just wanted to stick with what I've pretty much determined to be the correct parts for the purpose from all the obsessing and IPL rooting.

At any rate, we're gonna find out one way or another if the piston(s) situation has been the problem all along. I'm putting money on it since it has what is essentially a 5-10 / 6-10 three fingered transfer cast iron bore cylinder which calls for a full skirt piston, neither of which show up anywhere in any 7-10 IPL or on any of the piston and ring set lists I've seen for a 7-10.

Let's face it; Mark went way above and beyond with this saw doing everything under the sun trying to get it sorted out...., except changing to a full skirt piston. Thing is there, the prevalent consensus you read / hear these days says the newer 85239 thin-ring 2" piston is the miracle piston for all 70cc 2" applications regardless of cylinder type. Certainly no reason to think otherwise given such a prevailing opinion among most of the more experienced Mac guys out there, including Bob Johnson. And after all, an 85239 / 69030 was what was already in it when Mark acquired the saw. Who would just arbitrarily think of replacing it with a 'wrong' piston? No one..., 'cept maybe me? LOL

I'm certainly not casting aspersions toward Mark here and hope it doesn't appear that way. Quite the contrary. I'm simply theorizing a solution to a problem we were all trying to solve that he simply ran out of time to continue pursuing. He and Kevin already did all the heavy lifting. I'm just changing a piston to test what seems to be the last major theory not yet tried.

Can you guys believe it's been over a year since this saga began? I sure can. Boy, if it weren't fun...!

 

[vinnywv]

Show off day! Nice, fellas.

So I'm crunching IPLs again trying to determine whether I need an 85240 or a 69412 for this 3 finger transfer iron bore cylinder on the 7-10. Still finding more confusing info and differences among the various applications I've been able to find for both pistons -- including different wrist pin, bearing, connecting rod, and of course, ring numbers.

Gonna give Bob a ring after his nap and see what he has to say. Have a few more numbers to cross-ref first. Wish it was easier to identify the cylinders in relation to their pistons instead of them seemingly being numbered for all the various exterior fastening points / features instead. Makes it nearly impossible to match pistons and cylinders, especially for the 70cc series considering all the variations between just the p / c combinations alone..., not to mention the ambiguity (and downright inaccuracy in some cases) inherent in the available documentation.

And Vinny, any chance you could measure pin to crown and pin to skirt on those pistons? Kinda curious about those numbers, too.

From the top of the piston to the bearing top:
69412-0.575" 85240-0.575"
Bearing bottom to top of skirt arch:
69412-0.505" 85240-0.575"
Both measurements were from the inside of the bearing.

 

[vinnywv]

From the top of the piston to the bearing top:
69412-0.575" 85240-0.575"
Bearing bottom to top of skirt arch:
69412-0.505" 85240-0.575"
Both measurements were from the inside of the bearing.

Lets try that again, i may be dislexic....
From top of bearing,inside to the top of the piston on both is 0.575"
From bottom of bearing to the piston skirting arch is 0.504" on 69412 and 0.525" on 85240.