Nowadays, there’s no real justification for chopping the transmission off of a perfectly running Sportster motor. There used to be reasons to do it (see Little Big Twin Part 1), but that was thirty years ago. Today you’d have to be a tad nutty to decide to do this, so I guess that makes me a bag of peanuts. In a nod to the era of Sporty trans chopping, I donned the period appropriate upper lip protection and aviator-style safety glasses. I did most of the work with a cutting tool I’ve affectionately named the Flaming Sawzall of Death, but if you’re going to chop a Sporty I highly recommend a regular sawzall without a flaming blade.

I prepared for the chopping by stripping the motor down to the bare cases-anything that wasn’t permanently attached to the cases was removed. I thoroughly cleaned the cast aluminum so that I knew exactly where I would cut. Then, I modified a JIMS Sportster motor stand to support the cases once the trans (and rear motor mounts) was removed. I used a pencil to mark the cases for the notorious cuts I planned to make— taking extra care not to interfere with any part that might affect the seal of the crankshaft cavity.

With the precision of a back-alley abortionist, I first cut a notch into any section that wasn’t parallel with the table so that I had a comfortable 90-degree angle whenever I was cutting perpendicularly to the ground. I drowned the project in cutting fluid or WD-40 to lubricate the action and used fresh, aluminum blades for clean cuts.

Initially, I didn’t think I had to remove this threaded stud, but it ended up interfering with the sawzall’s path through the cases. Using an oxy-acetylene torch I heated up the case and was able to remove the stud with a set of vice grips and elbow grease.

In order to get around the odd shapes and sizes of the cases, and to prevent damage to the parts I wanted to keep, I used an assortment of cutting blades, interchanging them as necessary.

The two halves were kept bolted together for a number of reasons: no one makes a stand for half of a Sportster motor, together the two pieces are easier to handle, and I ran less risk of accidentally cutting into the crankcase.

The left side case was removed first, mostly because the other side is attached to the rear mounting plate.

An open belt primary was going to be required (because no one makes a bolt-on Sportster to big-twin primary), so I decided to cut down the original primary housing into a contoured front belt cover. It also saved me hours of cutting and grinding on the left side of the motor.

Check back soon for Little Big Twin Part 3, only on Bikernet.com!

On to The Next Installment...

Back to The First Page Of The Previous Installment...