Gearing suggestions...need 30~35mph out of an old MTD varidrive Signature 2000 Elite

So clearly this is not the kind of build you guys are normally dealing with, but it's what I'm working on all the same...the "race mower" forums all seem dead. I got an MTD Signature 2000 in pretty rough shape...but the engine runs BEAUTIFULLY and I think it's perfect to build a little hot rod that I can chase my kid and his go kart around the yard with.

My plan currently is to install a centrifugal clutch on the motor and, in the long run, just run straight to a live axle...ditch the variable pulley setup and factory axle all together and just do a go kart setup. For now, though, I want to try and make it work with the varying gears.

My questions at present are:

have any of you guys experienced issues running a large drive pulley mounted to a centrifugal clutch? Looking under there I'm thinking I'm going to have to go at least 8" on the drive side. I just didn't know if that additional mass would mess with how the clutches work.

~and~

have any of you guys managed to get the kind of speed I'm looking for out of the variable pulley? If that's just not something I can expect to pull off, then does anyone happen to know what the final drive ratios on these early 2000's axles are?

As far as the vari-drive thing, I think one big issue would come from over-speeding it. If you put a much larger pulley on the engine the vari-drive assembly would be turning substanially faster and it might wear out a lot quicker. Of course there could be ways to set up a grease fitting or two to slow down the wear, but I'm not sure. Also the ratio of those MTD single speed transaxles is very low because of the variable speed setup. I believe it's somewhere around 24:1. Also, welcome to the forum! Haha.

24:1 might not be impossible...

35mph comes out to about 36,960 inches per minute. A 20" tire has a circumference of 62.8 inches.

36960/62.8=588.5 (wheel RPM).

588.5 * 24 = 14125 rpm input

This engine has a 3600rpm peak...s0 14135/3600 = 3.92

So basically I need a 3.92:1 ratio...or approx. I could run an 8" up from and a 2" in the back...would probably lead to a lot of slipping. I'll probably have to run a jack shaft (will be slammed) so I could possibly get the variation that way. I don't think I could run the variable pulley that fast. The whole thing will really be spooled up.

If 24:1 is accurate I'll be better off going ahead and investing in the solid axle and pillow block bearings. Going straight to the axle I could run a 1:4 ratio and have access to a LOT more speed than I really need. It'll also be easier to set up a proper brake...but I'll loose the open dif (I will be on asphalt sometimes so this is a concern).

I have run a FNR tranny out of an mtd on my recently disassembled Murray and even tho it as single speed and topped out about 9 mph the bushing wore out and the grease failed and heated up the gears until they fused.

Were you driving the axle directly or still using the varidrive? What kind of drive ratio were you using to get your low flying 9mph?

I'll be swapping the grease out for oil if I go this route, but I'm pretty doubtful I will at this point. I also have a Murray and it has an actual transaxle...that might be my better option.

I was running an ungoverned single cylinder kohler with a 6.5 inch engine pulley, no vari drive, and a 5.5 inch pulley on the tranny. I even oil filled it after I fixed it and the bushings before that point were ok then after driving a while with the oil in it I could watch the slop in the gear set bushings. A spicer transaxle is a major improvement for a racing mower and a peerless is even better , look for a 930 or mst 205 or 206 model as they are oil lubed, but you can swap out the grease with oil on just about anything.

A Peerless 600 would be a nice choice too possibly because they are oil filled, have no shift keys, no reverse chain, etc. But yes, pretty much any transaxle would be an improvment over the FNR.

The peerless and spicer pieces would be nice, and I'll use one if I happen across one for the right price, but it's a hard sell to go out and buy one for this particular project lol. I'm just going to go with a kart type axle. It'll be easier and it's a known "works" solution...just didn't want to get that deep into it right at the beginning.

...depending on what the Murray has, anyway...I guess I need to go flip it over and see what's under it.

I'd recommend a Peerless 2300. Needle bearings, cast iron case, oil filled, H shifter, no reverse chain, pretty much the best of all worlds.

I'd like to post pictures of the other transaxle and see if anyone recognizes it, but apparently new members aren't allowed to post external links...if anyone is familiar with imgur then this is the tag for the album: a/Dt69uI4

Here is how to upload pictures to the thread.

Neat...I click the "attach" button just to see and this forum automatically gives my email address to an insecure third party image hosting site for the purposes of creating an account which can't be deactivated...and the site owners cannot be contacted through any link found on said site. That's lovely.