Building a SP125C / 101B Kart Saw

[Dennis Cahoon]

I finally nailed down a muffler.

Brad......that muffler doesn't even look like it belongs on a Mac chainsaw.......Put a round style muffler on it, at least make look like a Mac!

 

[Dennis Cahoon]

This is the type of muffler people switched to from stock who really used these saws in the woods. That funky Gem muffler belongs on a go-kart and will degrade the look of the famous 101B.

 

[blsnelling]

Brad......that muffler doesn't even look like it belongs on a Mac chainsaw.......Put a round style muffler on it, at least make look like a Mac!

This is the type of muffler people switched to from stock who really used these saws in the woods. That funky Gem muffler belongs on a go-kart and will degrade the look of the famous 101B.

Its that a Mac muffler or aftermarket?

 

[MechanicMatt]

Brad, I don't know if it'll work good on your motor but my buddies all run carbon fiber reeds on there sleds. Oh SNOW MOBILES. Ive heard sleds called all different things. But you know what I mean. Good luck!!

 

[Arrowhead]

Yeah I agree with passing on NOS Mac reeds unless it's just a shelf queen that you're going to run for short periods every once in a great while.

Some of the kart guys are switching to reinforced Carbon Fiber reeds which I've heard good things about. There's also some modern two-stage Boyesen reeds that fit the Mac cages. One group of the karters got together and had a batch of reeds made custom by Boyesen.

I run the 2 stage Boyesen reeds in my 6 cube Pioneers. They work awesome.

 

[cpr]

Its that a Mac muffler or aftermarket?

Mac. Came on a bunch of different saws.

 

[rwoods]

Brad, to each his own. If you are trying to build a stock appearing 125 then you should use the 797 rectanglar muffler and a 125 muffler guard. if you are building a work saw, the round muffler is the way to go - much easier to replace the chain and you can adjust the direction of the exhaust. I have to be careful not to start a fire but this is what I am going to put on my kart saw except it will be painted black:

Ron

 

[blsnelling]

I think stock appearing is out of the question already with the intake and carb I'm going with. This will not be a work saw at all, just a GTG toy.

 

[gink595]

When I was into dirt bikes I had a CR250 I put the Boysen 2 stage reeds in and it made a huge difference in the power delivery. I remember at one track it was always questionable if I could get enough speed coming out of a corner to make a double jump, after I swapped those reeds out I never had that issue. The power came on alot quicker. I was sold after that.

 

[blsnelling]

Does Boysen have a stock PN for the Mac reeds? Or, were these a special group buy by the kart guys? These reeds look ancient and I definately want to replace them.

 

[Jacob J.]

Does Boysen have a stock PN for the Mac reeds? Or, were these a special group buy by the kart guys? These reeds look ancient and I definately want to replace them.

It was a special buy. They bought 100 sets. I don't know if that was the minimum order or not.

 

[Busmech]

I run the 2 stage Boyesen reeds in my 6 cube Pioneers. They work awesome.

Brad when I first started messing with 101s I contacted Boyesen about reeds, they had me trace a set of the v4 reeds with a sharp pencil and fax it too them. Turned out they had a set for a personal watercraft that matched perfectly, only difference was the size of the screw hole (had to be drilled larger). I will try to find the part # don't hold your breath tho it's been a long time. Also I prefer the GEM v4 reed block and reeds to the mac, I believe they flow better.

 

[blsnelling]

Brad when I first started messing with 101s I contacted Boyesen about reeds, they had me trace a set of the v4 reeds with a sharp pencil and fax it too them. Turned out they had a set for a personal watercraft that matched perfectly, only difference was the size of the screw hole (had to be drilled larger). I will try to find the part # don't hold your breath tho it's been a long time. Also I prefer the GEM v4 reed block and reeds to the mac, I believe they flow better.

That would be awesome. Where they a 2-stage reed?

 

[Busmech]

No they were just a flat reed.

 

[Busmech]

Brad, check ebay item#110770597607 that is the GEM settup I referd to.

 

[rwoods]

I think stock appearing is out of the question already with the intake and carb I'm going with. This will not be a work saw at all, just a GTG toy.

With this thread everybody will know that your saw ain't stock but the man from down under's stock appearing saw is what got me started on gathering the parts. Unfortunately, I get outbid on every single pumper BDC that comes to my attention so I am going in a different direction as well. Ron

 

[Busmech]

With this thread everybody will know that your saw ain't stock but the man from down under's stock appearing saw is what got me started on gathering the parts. Unfortunately, I get outbid on every single pumper BDC that comes to my attention so I am going in a different direction as well. Ron

Look for an HR tillotson, much more common than the bdc macs, parts are easier to find also.

 

[Jacob J.]

Apart from the BDCs, there's some other good running large carbs out there, like the Tillotson HR and some of the bigger Mikuni diaphragm carbs.

 

[blsnelling]

Brad, check ebay item#110770597607 that is the GEM settup I referd to.

That's a sweet deal for the price. I grabbed one while they're available. I'm still going to check into the Boysen 2-stage reeds though. Thanks for the heads up.

 

[Ambull]

OK Brad, I put together a vid to show how I start a 101B Mac. This one is .050 over, 129cc, no decomp. It has fresh rings, and I notice the compression has been on the rise, as it is getting harder and harder to turn over. Not the best cut, as I realized the filter was dirty after I made the cut.

[video=youtube;imVCsFHAx-g]http://www.youtube.com/watch?v=imVCsFHAx-g&feature=youtube_gdata[/video]