MCCULLOCH The official McCulloch thread

[Squareground3691]

We’re Terry (Legend) Ives, Lol

 

[Bigmac]

Yeah, I know! But that’s what guys do because they don’t let them warm up and run the piss out of them! With good machining and the size of the piston .0025 shouldn’t be a problem at all, should be able to do .002 but I haven’t gotten that brave yet!

 

[Mastermind]

We’re Terry (Legend) Ives, Lol

I talked to Terry a few days ago. He's 83....and doesn't seem like he's ready for retirement yet. I'd be happy to still be in the game at 83.

 

[jacob j.]

I talked to Terry a few days ago. He's 83....and doesn't seem like he's ready for retirement yet. I'd be happy to still be in the game at 83.

Terry is amazing. He's been working on these motors for over 60 years.

 

[Squareground3691]

I talked to Terry a few days ago. He's 83....and doesn't seem like he's ready for retirement yet. I'd be happy to still be in the game at 83.

Can’t even imagine how many Mac’s he put together and developed,

 

[jacob j.]

Ya .003–.004 , some of the kart forums state .0075-.0100 for race clearance. At .003 I like and extra long break in and letting it idle and get really warm before any cuts. I usually let my 101’s idle for at least a half hour with some revs for break-in before I make any cuts breaking that up several times

I've been going .0045-.0055" on mine, depending on bore size. All of my recent builds have been larger bore sizes (0.030"+). I went .0055" on my .060" over 101b in my dad's old saw. I'll be building an .080" over 125 iron-bore motor this summer and will go probably .0055-60" on that one.

 

[Mastermind]

I've been going .0045-.0055" on mine, depending on bore size. All of my recent builds have been larger bore sizes (0.030"+). I went .0055" on my .060" over 101b in my dad's old saw. I'll be building an .080" over 125 iron-bore motor this summer and will go probably .0055-60" on that one.

I'm gonna split the difference. .004" is the target. LOL

 

[Bigmac]

I've been going .0045-.0055" on mine, depending on bore size. All of my recent builds have been larger bore sizes (0.030"+). I went .0055" on my .060" over 101b in my dad's old saw. I'll be building an .080" over 125 iron-bore motor this summer and will go probably .0055-60" on that one.

I have had Terry set up a few of mine a little tighter. Than his usual. And they have been good. All of my bigger bore fordged pistons quad stuff runs a lot tighter, blaster 2mm overbore pistons that are 68mm need .002 clearance and my 81mm pistons need .0045,
I just think some of the clearance is excessive. I know they run with it, but I think it’s mainly from inadequate warm-up time

 

[Mastermind]

I have had Terry set up a few of mine a little tighter. Than his usual. And they have been good. All of my bigger bore fordged pistons quad stuff runs a lot tighter, blaster 2mm overbore pistons that are 68mm need .002 clearance and my 81mm pistons need .0045,
I just think some of the clearance is excessive. I know they run with it, but I think it’s mainly from inadequate warm-up timeView attachment 456198View attachment 456199

Usually a forged piston requires more clearance than a cast piston. .002 sure seems really tight for a forged slug.....but I think Wiseco knows more than Randyco. LOL

 

[Bigmac]

Usually a forged piston requires more clearance than a cast piston. .002 sure seems really tight for a forged slug.....but I think Wiseco knows more than Randyco. LOL

Yeah, I don’t know either. I just tried to follow the best advice I have, and experience.

Been running the tight end of Waco specs for a long time now and have been very happy, once I learn proper warm-up time the results have been excellent.. I use the blaster piston in banshees for years now, made 109hp with 2 at 10,000 rpm and am running a 78mm bore at .0035 and it has lots of hours on it

 

[Squareground3691]

Yeah, I don’t know either. I just tried to follow the best advice I have, and experience.

Been running the tight end of Waco specs for a long time now and have been very happy, once I learn proper warm-up time the results have been excellent.. I use the blaster piston in banshees for years now, made 109hp with 2 at 10,000 rpm and am running a 78mm bore at .0035 and it has lots of hours on it

Good prep work pays off,

 

[Mastermind]

Yeah, I don’t know either. I just tried to follow the best advice I have, and experience.

Been running the tight end of Waco specs for a long time now and have been very happy, once I learn proper warm-up time the results have been excellent.. I use the blaster piston in banshees for years now, made 109hp with 2 at 10,000 rpm and am running a 78mm bore at .0035 and it has lots of hours on it

Nothing beats experience.....and you've gotten it.

 

[hacskaroly]

I usually let my 101’s idle for at least a half hour with some revs for break-in before I make any cuts breaking that up several times

Is this for initial use of a new piston and rings or normal warm up for use? I like how the people on YouTube fit in a new piston and then gun it within seconds of starting it...lol

 

[Bigmac]

I get at least a half an hour of break in warm-up, I like to get all of my stuff up past operating temp for at least a half hour, and I don’t ride my quads until water. Temp is at least 120, if it’s cold out, that can take a while if it’s hotter, it might not take that long, I have taken a heat gun on my 101’s to at least get into the 120-150° temperature before making any cuts, and once you know what that feels like by touching the fins, you have a pretty good reference, it’s pretty dang hot

 

[Bigmac]

Nothing beats experience.....and you've gotten it.

There’s always more learn! Wiesco’s also tapers their pistons, not sure on all the Mac and all of the Burris pistons

 

[hacskaroly]

I get at least a half an hour of break in warm-up

Makes sense. When I replace a piston or piston and cylinder, I let the saw idle through a tank of gas first.

When I started working retail, anytime we sold a Stihl, we had to start it, so we would gas it, start it and full throttle until bar and chain oil starting creating a skid mark on some cardboard. I didn't like that procedure and after getting Stihl training, I would always let a saw idle for at least a minute and then would only trigger enough to get the chain spinning to where it would start slinging some oil. I would blip it to make sure it didn't hesitate going to high speed, but that was it. I would then let it idle for a minute to cool down and then take it out to the customer.

Warming up the engine definitely extends its life!

 

[Bigmac]

I'm gonna split the difference. .004" is the target. LOL

Wouldn’t hurt to talk to Terry again and get his opinion! He is definitely the authority on it

 

[Mastermind]

Wouldn’t hurt to talk to Terry again and get his opinion! He is definitely the authority on it

Good plan.

 

[heimannm]

Pistons are tapered (larger at the skirt) and the clearance (piston to bore) is very generous by the book.

 

[Al Smith]

FWIW years ago when I did an iron sleeve on a 125 Mac I used the charts on one of my Mac micro fitche charts and used the mean average which worked out to 4 thou .It would stand to reason an aluminum piston would expand more than a cast iron sleeve .Plus I surmised a semi slipper style of piston would expell the heat as it dipped down into crankcase in rotation .All that was just a guess on my part .Saying that it seems to run okay but in the12-15 or so years ago I did it I haven't put enough run time on it to seat in the rings .