This post is about converting rear drive chain to rear belt for pre 65 transmissions

This ain't a chain vs belt discussion

Some background

In the early '90s, I had a rigid evo that I built with a pre '65 4 speed ratchet top tranny. I wanted a rear belt drive, and Karata was pretty much the only game in town that made complete bolt-on rear drives for about any HD that didn't originally come with one. I believe the kit was like $650 at the time for a BT with rigid frame, kick only

For BT's, the Karata rigid kit I needed came with a front pulley, rear pulley, and the rear belt. It was an easy bolt-on. I had that setup on that rigid evo for a few years. Later on, I built an evo softail and used the same tranny and rear belt drive kit: It was a direct changeover and I NEVER had a problem with that rear belt conversion. I'm talking thousands of interstate miles, almost 500 miles one way in the summer heat and then dirt roads to parties

So for something a little different:

I wanted a rear belt drive kit for my current project, 60 pan in an OEM 1970 swingarm frame

Understand, I have an open belt drive, pre 65 tranny with ratchet top, no inner primary or bearing support

So I went to the Karata site, and while the site is up, they don't really sell rear belt drive kits anymore. Bottom line, they no longer sell the conversion kit I needed or parts for them anymore: I couldn't find any other belt drive companies that sell conversion kits anymore for older (pre 65) tranny setups

So I said fuck it, I'll get one together, one part at a time

The following is for a SWINGARM rear belt conversion (I'll go over a rigid frame conversion at the end)

I based my conversion idea on the 1980-82 FXB Sturgis ("B" for belt). It was a dual belt (primary and rear) that HD tried out. It only lasted two years because the primary belt had a reported habit of failing (This was because of mostly home mechanic error by misadjusting the primary belt)

After research, I found the FXB used an early style clutch basket, same as used on the older 4 speed (pre 65) ratchet tops, the only real dif being the main shaft on the FXB was longer for the use of an e start.

So I'm thinking I'll just order the tranny pulley for an FXB, and it should fit just right on a pre 65 tranny main shaft as the splines are exactly the same. The hardest part to source was finding the 1981-1982 FXB trans pulley: V Twin had them at one time but quit stocking them. And no fucking where on the net had them. But I contacted a Jay, and he found some about a month later thru V Twin (They started stocking them again) I'll post part numbers/costs at the end

So I get the trans pulley, cool: And it fits right on my ratchet top tranny, pre 65 main shaft perfect. Keep in mind the trans pulley is a 33 tooth

So then my next question was, what tooth rear pulley should I run? I went to the Karata site and found a chart with the ratio info I needed: 33 front, 70 rear. So I go to ebay and get like a 90's era rear pulley, 70 tooth that will fit my rear rim (3/4 axle)

Now what size belt?: 1 1/8" wide, 125 teeth, 14mm . It took me forever to figure out what belt size (tooth count) I needed. Now to find one: Found out it's the same as what's run on a 91-99 sportie: I found one on ebay, cool

Since I am now running a 1970 swingarm frame (not a rigid) an extra step is involved: You have to have a swingarm that has a kick out on the left side that allows for both belt and rear pulley clearance: I found a used 1982 FXB SA on ebay: Fits my 70 frame perfect. Paugho makes a replica SA that will work, but I don't know the number right now.

So I go to put everything together..........

The trans pulley fits the main shaft perfect, BUT: Since the FXB pulley is like two inches wide,(the Karata version was only 1.5" wide) the bottom of the clutch basket hits the pulley: I was confused for a while and then figured that since this pulley was originally made for the longer e start main shaft (1981-82 FXB) that is why it's touching: I have a non-e start main shaft, which is shorter: SOLUTION: I cut the pulley back to 1-3/8" wide from the outboard side = perfect fit

Rear-wheel spacing was easy. Just ensure that the belt tracks perfectly on both pulleys w/o running off. The belt doesn't have to run exactly center on both pulleys. Just be sure it doesn't run off the side of either or contacts any part of the frame. Triple check the alignment, then do it again just to be sure: It was an easy deal for me, no issues. Once you get the belt adjusted, it's fire and forget. Interesting note, my 1.5" wide belt fit just right running a tin inner and outer primary cover on an older build using a Pan motor

So now I have a dual belt, kick only, swingarm panhead: I also found that the rear belt guard on all factory rear belt, 4 speed swingarm HD models bolts right on, and ebay has plenty of them (Got one for $30)

Want to talk smooth?: Trust me, the ride is……

Costs/Part numbers?

33 Tooth 14MM front pulley: VT 20-0449 $130
(1990's era 70 tooth rear pulley, 14mm EBAY $70
Rear swingarm from 81-82 FXB $75 (ebay)

Rear belt, 125 tooth, 14mm $160

For those with a rigid frame:
You will save $$ as you don't need a swingarm: If I remember correctly my old build in a rigid frame (no inner/outer primary, pre 65 tranny, kick only) had enough clearance for the rear belt and pulley in the Karata kit (1.5" wide): But the rear belt you will need for a rigid frame will need a rear belt will vary

Hope this helps for those wanting a rear belt drive on their rides using older trannies

Pics coming