rearenginekarts.com

I have found myself scarce on the forums over the last few years.....been building my cabin and shop out in the sticks deep in the east woods of Texas. To avoid the craving of anything mechanical/motor/wheels etc, I only allowed myself to work on some dinosaur chainsaws. Since my new residence is located in a dense forest of oaks and hickorys I still need to keep the trees at bay. But the reason to visit, or just a excuse maybe, I dont really know for sure, is in search of some parts.

From some of the saws I have left over, there are enough parts to resurrect one or two nice 44/55 model Macs. Actually using all of the donor parts to fix the 55 gear reduction ones.

I figured several of you have purchased some NOS pistons for use just to realize when they arrived were not the right size. The D44/55 saws have just a 2" bore, otherwise look just like any other piston for the early kart motors.

So if any of you happen to be sitting on piston/rings set that is 2" for a Mac saw and dont have use for it, I would be very interested. I can bore the blocks in case you have any oversize ones too.

The other item is a bar around 24" or longer and/or chain with 1/2" pitch. This size was used on gear reduction models on Mac saws. Most of the bars were interchangeable with 404 chains used on early direct drive models. The 1/2 chain is huge in comparison to whats on new style saws and didnt really wear out so much. With a roller bar and adequate oiling would rarely even need adjustment.

I will drop a post in the for sale/wanted section, but since the traffic seems a little bit light as of late, thought this may generate some kart related responses here too.

Thanks for any help.

Terry,

Here are kart piston bore sizes. Don't know how much overbore you can go.

Perhaps Bob Corwell will chime in with a piston source, he's a saw guy.

Model - Bore Stroke Displacement
MC2 - 2.165 x 1.635 = 6.05
MC5 - 2.125 x 1.375 = 4.9
MC6 - 2.125 x 1.500 = 5.3
MC7 - 2.165 x 1.635 = 6.05
MC8 & 9 - 2.165 x 1.635 = 6.05
MC10 - 2.125 x 1.500 = 5.3
MC20 - 2.125 x 1.635 = 5.8
MC30 - 2.165 x 1.635 = 6.05
MC40 & 45 - 2.165 x 1.635 = 6.05
MC70 - 2.217 x 1.835 = 7.08
MC75 - 2.250 x 1.835 = 7.29
MC49 - 2.125 x 1.375 = 4.9
MC90,91,2,3 - 2.165 x 1.635 = 6.05
MC100 - 2.250 x 1.835 = 7.29
MC101 - 2.280 x 1.835 = 7.5

Good luck with your search.

R.E.A.R.

Thanks for the info. The D44/55 saw motors only have a 2" bore. Unable to punch out to the smallest kart engine bore of 2.125.(Mc 1/2/5/6/10 compatible) At least without resleeving. Thats too much trouble. Even tho these little 4.4 CI motors run well, they lack a little for kart use. Unless someone is cloning a Jimmy Yamane kart with two of them in chainsaw format. I just hate to see the parts sitting around if they could be made into a decent gear reduction saw or two. I have Supper 55A saws in use but they run and dont need any repairs.

Just thinking someone may have purchased a piston hoping it was the correct one and find out it fits these earlier saws. I figured there are plenty of these saw motors sitting in pieces since they have the elusive parts to clone a real Mc 10.

My last dirch option is just machine a set of rings and use the old pistons. They were only made from cast iron on early models and later replacement parts with a chrome plated top ring.

To curb my urges I was planning to 9 port one of these saws and add a modified Palimini header for the cool factor. The first generation of the D44/55 motors came factory with squared exhaust ports. No sense not to add a few more ports to help out a little. Then maybe a larger Tillotson to help breathe a little better.

See here I go again getting side tracked from finishisg building my cabin in the woods. AH! The humanity of it...

These pistons have the thick cast rings?
I would look at breathing more than a larger carb. Saws are usually pretty restricted in that area.
I have some 250, 350, 15 saws & I keep one running for yard work. They are all stout pieces.

These particular saws have governors, which I do want to keep in use. So a larger carb would have limited benefits. Opening the venturi from 11/16 to 3/4 would improve a little. But the intake tract is so restrictive, not much reason to get too carried away.

Lots of that old Mac chainsaw stuff still around. Ebay is the first place I would hit along with some of the larger small engine parts suppliers. Also cast rings were used in lots of other engines so if you can find the bore size and width......... your there. Don't matter what box they came out of.

Fitting/filing oversize rings to a standard bore I believe would be preferred over boring. leaving an end gap of .012"-.018" would have best results. That is unless of course you're replacing the piston with an oversize. Don't forget to chamfer ports and break the sharp edge ever so slightly, I suspect all this is already known and is for benefit of anyone that may read down the line.

I could use standard size rirngs, Basically something with less than the 1/4" end gap like these have. Right now I have a bunch of 2" 0.024" thin rings, some thick rings that measure 0.057" that almost work, but the side clearance is too excessive. The 1/16" rings I have are either 1.875" or 2.125" I have also located some nice hard chrome over steel rings that are 0.039" thick. These would be perfect if I cast some new pistons with a single ring groove.

I had just hoped with all of the Mac saw parts showing up over the last ten years someone my have picked up some 2" bore thinking they might work for a saw motor. Several years ago there were some showing up occasionally, but I didnt plan at that time to resurrect any of these parts saws.

Simple case of "If you snooze you loose". I will keep my eyes open and maybe get lucky.

Well Terry just read your post I don't mess with them there little critters i'm into big boys toys over 100cc.

So a bit of a blank here i'm afraid good luck with the D-44/55

McBob

Found a set of rings. Thanks to Mark Loraine for posting some part numbers.

The big saw motors would be fun to play with, but I am sitting on too many of the early saw parts. After running down D44/55 donors for Mc 10 parts then the 1/70/80 for the rest, I cant just toss these leftovers away. Since they work great when running, I keep them busy with a small jungle that needs attending to on occasion.

I had the diluted idea a few years ago of machining a new intake that sticks straight up and accepts a decent reed setup with K&N style filter topping a newer HL or HR carb. Then adding the boost ports to go along with the factory squared exhaust ports. As entertaining as that could have been for a while, I just need a few good working saws. I favor these older gear reduction models. But the 1/2" pitch chain is getting harder to locate.

I do have a bunch of the David Bradley gear reduction saws. Mostly the 5.8 and 7.98 CI models. What were destined to become kart motors, got left as working saws. These still show up locally all the time at decent prices. When cleaned up and running well, they do get a lot of attention from people.

A few years back I restored a big gear reduction David Bradley saw my grandfather had bought new. I did it for my dad when he turned 70. It sure turned out well and nice looking. He built a shelf in his barn just to sit the saw on for anyone visiting to get a good look at. It was a running saw that day, but never was put back into service. From a little kid, I always remembered that big massive saw that was to heavy for me to pick up, and glad I had the interest in it. Otherwise it would have been long gone.

I helped a friend clear away a bunch of trees recently with these old saws that I do have running. They were being temperamental as usual. Too much sitting up and lack of use mostly. I always brought several of them, so to have at least one running when needed. He decided to go ahead and buy him a couple of new ones. A big Husqvarna and two Stihls later, I am constantly having to fix them. Starting to see a pattern with equipment that only gets occasional use at best. Clogged carbs, fuel lines disintegrating, dull chains, bad gas, the usual for most lawn equipment.

I finally changed to aviation fuel in everything I own. Including the 4 wheelers, weedeaters all of the saws, kart motors, and vehicles that only see occasional use. For all the years I raced, it never let me down.