rearenginekarts.com

Hey guys,

New here, looking for some info on the Mcculloch MC91 M/C motor, I have one on my '60 Go Kart 800, as im trying to research as much as i can about the motor and parts for it. It has a Walbro SDC carb on it currently, but im looking to possibly upgrade it to a Tilloston. Anyone have any idea of where I can find info on what kind of power/displacement it has, and where I could find a better carb. I'll post pictures when I can, currently not home, will update the post with pictures once i can.

Thanks,
Adrian

(P.S, Upon disassembling my motor, i have found that it was once red/white. I have found the correct color codes for it, just wondering if anyone has pics of the red/white variation of this motor.)

**edit**

Motor was correctly ID'd as a 49, not a 91.

Red and white were usually the industrial version. Does it have the 9/16 tapered crank or the 3/4" straight crank?

3/4 straight

By the way, how do you upload pictures? I cant seem to figure out how/where.

Old school. You need to use a picture hosting service. Sorry.

You have the industrial crank. 91 series usually run 9t on the crank for sprint racing. 3/4" crank I think the smallest clutch drum you can run is a 12t. So you have 2 options. First is you can get a kart crank instead of the industrial crank or you can use what is called an arena clutch but even those only go down to 10t I believe.

Rob Voska wrote: ↑

Mon Sep 26, 2022 8:43 pm

Old school. You need to use a picture hosting service. Sorry.

You have the industrial crank. 91 series usually run 9t on the crank for sprint racing. 3/4" crank I think the smallest clutch drum you can run is a 12t. So you have 2 options. First is you can get a kart crank instead of the industrial crank or you can use what is called an arena clutch but even those only go down to 10t I believe.

Thanks, good to know. So is my motor still classified as a Mac 91 motor or some other specification? also, I would love some technical specs of it if anyone knows of them (ie: how much power they make, displacement, rpm range, etc..) (fyi, i have a 12t clutch on it right now, seems to work fine for my setup, although once i finally get it into proper running/driving order i most likely will upgrade the crank like you suggested. I do plan on racing it and might bring it out to TBO next year if i can)

Look here.

http://rearenginekarts.com/phpbb3/viewt ... f=1&t=4694

MC91, Bore 2.165, Stroke 1.635, Cubic inch 6.05

Depending on mods and exhaust system 9-12hp ish.

RPM? I don't use a tach. Depends on a lot of things but I have heard 12-13000 RPM.

Rob Voska wrote: ↑

Mon Sep 26, 2022 10:22 pm

Look here.

http://rearenginekarts.com/phpbb3/viewt ... f=1&t=4694

MC91, Bore 2.165, Stroke 1.635, Cubic inch 6.05

Depending on mods and exhaust system 9-12hp ish.

RPM? I don't use a tach. Depends on a lot of things but I have heard 12-13000 RPM.

Wow, thats a lot more than i expected! one more thing. Should i keep the walbro or swap it for a different unit? if i do, what carbs would fit this motor/what would you suggest for it?

Thanks,
Adrian

finally figured out how to upload images, heres a pic of the kart:

mostly origional, was a family members that sat in a basement for a couple decades, was origionally red, then it was painted blue by the previous owner, so a few years back i rattlecanned it red again. put a lot of work into it, and its almost done.

Hard to tell from that picture. Are the mounts welded to the frame or a swing type of mount? Looks like a Go-kart 800 or 1200.