McCulloch SP125C replacement Carburetor

[Bubba Stump]

For exhaust, I have a new GEM muffler. As far as carbs go what would you recomend I try and obtain? I thought that the carb I had was not big enough. I don't know if there are any other tillotson carbs that will fit my gem west bend 820 reed cage so I might have to look for a sloped mcculloch intake or come up with something from scratch. I could probably make my own like you did. I made my own intake manifold adapter for my Suzuki samurai trail rig and it works as good or if not better than the My-Side kit that ZUKSOFFROAD sells. I don't know if you have any experience with samurais but the my-side kit is and adapter that lets you run a harley davidson 40 or 44mm keihin carb instead of the stock carb. anyway, I have a plasma cutter, tig welder, mig welder and a many years experience fabricating things to be able to build my own intake the problem is just finding the time to tinker with it. I might be able to just have a machine shop make a more slanted adapter block for the intake I already have. Do you have any pictures of your setup that you would be willing to share?

 

[leeha]

PM me your email, i will send a pic of my set up.

 

[sachsmo]

Hey Unc!

 

[Bubba Stump]

O.K. guys here is the finished SP125 that this thread was about. So far changing the polarity on the ignition chip worked and it is running awsome. I have not yet put it to the ultimate test in a big log but it sounds great. The other two saws are my Stihl 084AV and my first SP125 that I ever owned. All run great but I would have to say that the 084 is the king of the lot. I can run it with the Cannon 50" bar, Carlton .404 .063 full skip chisel chain and a piltz 9 tooth sprocket and it will throw buckets of chips withn the bar burried in a log no problem. After I get all the kinks worked out of the newly rebuilt 125 I might change my mind on which saw is the king of the lot. I have also included some pics of the parts I have gathered so far for my next mc101c powered saw that I want to build.

 

[sawfun]

Nice collection, bet a lot of guys are drooling over that long Mac bar. I didn't know Mac made them that long. That bar is likely worth more than the saw. Your 084 might spin faster but it won't have the torque of those Macs. My 088 & 880 sure didn't when stock.

 

[Bubba Stump]

Nice collection, bet a lot of guys are drooling over that long Mac bar. I didn't know Mac made them that long.

The bar is actually a Cannon Superbar that was for a Husqvarna and I modified (oil holes)it to fit the mcculloch and then I blasted it and painted it with the help of chainsawr.com and there bar stencil they sold me.

 

[sawfun]

Man, that looks great. It did look like a 3 rivit tip bar. If you still have the stencil, wanna do a couple for me. Or sell me the stencil ?

 

[Bubba Stump]

Man, that looks great. It did look like a 3 rivit tip bar. If you still have the stencil, wanna do a couple for me. Or sell me the stencil ?

The stencils were the one time use kind that are like a sticker that you put on, paint and then peel off and throw away. chainsawr.com sells them, I think a set was like $12+ shipping. I painted the middle of the bar mcculloch yellow where the stencil would go and after it was dry enough I put in the stencils and then painted the bar a flat engine enamel black. Took a little bit of time to do but it turned out nice. Oh, I forgot to add that I lightly blasted the bar with some baking soda and sprayed a mist of water with white vinegar on it before I painted it. That is a little trick I learned from a old timer that used to do custome paint jobs on hot rods. He told me that the vinegar would act like a acid and etch the metal and the paint would stick better.

 

[Bubba Stump]

Hey guys, its me again. I have been testing out the 125 running the 50" bar and it is pulling it real nice and so far the polarity change on the ignition chip did the job and the saw has been running awsome. I am still trying to find a better carb to replace the stock one so that I can give the old beast a bit more power. I want to try and see if the saw will run the Cannon 72" roller nose bar that I have but I need some info on what kind of chain I should get for it. I assume that because the bar is a roller nose, I don't have to stick with the .404 pitch, .063 gauge chain that it was made to pull. Would I be doing any better if I ran a 3/8 pitch, .063 gauge chain instead? I guess my question really would be, Since the saw is not a kart motored saw, what chain would run better on the 72" bar with the stock powered saw? Do I go 3/8's, .404, round chisel, square chisel, or is there something better I can run that I don't know about. I am guessing that the chain that I will eventually get will probably be close to 200 drivers. I will be running a 7 tooth sprocket. Any technical info would be much appreciated. The 50" i have on it right now is running a .404 pitch, .063 gauge carlton square chisel in full skip sequence with a 7 tooth .404 sprocket and it runs it no problem.

 

[watsonr]

a .404 7 is about the same size as a 3/8 8 and the .404 8 is about the 3/8 9. So if you switch, go to a 3/8 8 minimum or stay with .404. There isn't that much of a difference in the kerf between the two chains, 3/8 is smaller. It also would take less power to pull 3/8, but will dull faster. IMHO, I'd do .404 7 for a 72" bar. Stay square grind, full skip and be smiling for months!

I see, no luck on the SDC20 carb yet. Saws look good.

 

[sawfun]

Go 7 pin & .404 for a bit more strength on that length chain. Even a SDC carbed 101b does not like 8 pin all that well on 36 & 50 inch bars. I am gear driving a cp125 for the exact same 72" Cannon bar that you have if that tells you something. Use an SDC 20 carb on the sp125c for a bit more rpm.

 

[rwoods]

A word of caution on your next project - I love the GEM muffler but you need to safety wire, find some other mechanical means to secure the two interior attachment bolts, or frequently disassemble the muffler and tighten them, otherwise you may end up eating one. So far so good for me but it is a pain to keep them tight. Ron

 

[sawfun]

My GEM muffler, if you can call it that, has nothing inside. Its just a cool looking box that bolts to the 101 but not a 125.

 

[rwoods]

GEM mufflers like Bubba's and mine have an internal baffle - a SS perforated plate (not shown in my pictures). The angle exhaust is good for keep sawdust away from you. These mufflers are designed for the recessed exhaust of the Kart engines but you can run them on a 125 - they just stick out - and pose a burn hazard.


Check out the branding where the saw hit my leg as I was lugging it back to the truck.



Ron

 

[sawfun]

This is what mine looks like

 

[Bubba Stump]

Great info guys, thanks for the help. I only have the parts in the pic and a few other odds & ends for my next build. I have been doing some research on the models of McCullochs that were made to pull the long bars and like the info I found on the modified 890's and 895's with the 101 kart engines. Since I do not yet have a saw to build my next project off of I am toying with trying to find a 890 or 895 to put the 101C block into. I don't know how hard it is to modify these saws with the 101 so I am stuck on what to do. I either build a 101 powered SP125 or go with a 101 powered 890/895. my other option is to find an 890/895 and put a mc91-up block in it. I have aquired some really nice mc91 kart parts that are really rare and would make a very nice build among some of my parts for the mc91 is a good Billit Aluminum Hyperode Connecting rod that is made for the real high reving karts.

 

[sawfun]

The 101 block may not accomodate the gear drive very well. Speed is not usually as important as torque when considering a gear drive. Also there are 2:1 & 3:1 gear ratios and 7 &8 tooth .404 drive sprockets for changing effective gearing. A direct drive 125 with a kart engine makes more sense.

 

[watsonr]

The 101 motor on a 125 drive will be the fastest as well. I've got an 895 drive with an MC100 motor, easy build and fit well, as fast as a direct drive saw and even with a 36" bar, can't slow it down. She will be wearing a 50" most days.

 

[minermike]

Those chips do not work on the 125s. I have tried two different chips on two different 125s. The best thing that you can do is switch the saw back to points. The chip will make the 125 hard starting and backfire. It also won't let the saw rev correctly.

I know this is a super old post but we use chips in all our mac race saws and putting a 101 in a sp frame is a piece of cake. takes an hour to do it. i have built a ton of 101 125 race saws and anyone can do it .all our saws start on a half a pull with a std. flywheel and 30 degrees of timing with a nova chip positive ground wired. .

 

[210-262-9321]

thanks for the info , I'm building a SP125 now Aug 2023!