Fish's Dirtbag Challenge 2018 Build

Dirtbag Challenge Build 3: Of Stopping, Sissy Bars & Safety Pins

In my last update, Project SnoMoChop was a roller accompanied by a long list of details to make it something more. I’ve been working my way through that list, and with the help of Craigslist, have made some serious progress.

Things that roll eventually need to stop, and the dirtbike brake that came along with the Husky front end is certainly not up to the task of stopping this potential rolling deathtrap on its own. For more reasonable whoa, I visited Contra Costa Cycles in Concord. They’re the kind of shop that doesn’t keep a lot of new parts around, but they’ve got shelves and shelves of cast-off bits and leftovers from a lifetime of building bikes. I was hoping for a 2000-2005 Dyna rear caliper, as the anchor is fairly simple and would interface with my axle and rear wheel with minimal work. As luck would have it, Joe (the owner) had just such a caliper on hand. As a bonus, he had an axle and a box of spacers I could pick through to help my cause. The best part? Only $60 out of my budget.

Next on my list was a fuel tank. I was originally considering a set of cast-off five-gallon split tanks for maximum capacity, because two-strokes can be thirsty. However, Joe happened to have an aftermarket chopper tank on hand that I thought would look absolutely perfect on SnoMoChop’s rigid frame. Another $40 out of my wallet, and I was fastening it to the Giant Loop bags on my CRF250L Rally with baling wire. Note to self: always carry straps.

The postal service had been by while I was out and left behind a package containing a couple rear sprockets from my dad. That gave me all the parts I needed to assemble the rear wheel.

The first order of business was to make some combination axle support/chain adjuster blocks. My rigid frame was intended for a 7/8″ axle, but I am using a more modern 3/4″ part. $40 spent at McGuire’s Harley-Davidson provided the required stepped adapters. Given more time, they could have been milled, but even low-budget projects require balancing time and money. I did have to modify the spacers—the original design only pushed against the axle, and did not locate it against braking forces. Apparently the original drum brake assemblies didn’t exert the force modern disc brakes do. On the advice of my father, I welded some threaded rods into the notches intended for forcing screws, and locked those threaded rods into the original adjuster bosses on the frame. Voila! Chopper magic!

The brake caliper was not so simple. The stacking of spacers required to hold clearance for the sprocket on the left side meant that the axle boss on the caliper was simply too thick. As a matter of fact, it was exactly ¼” too thick. Machining would have to happen.

Or, a makeshift jig to fixture the caliper to my belt sander. With enough patience and a fresh belt, this crude setup gave enough clearance to slide the caliper home.

The anchor plate for this style caliper is simply a ¼” thick steel tab: easy enough to duplicate and weld on. The finished product looks as if any other chopper builder would have done the same.

One of my goals for this build was to use scooter-style brake actuation. I figured the CVT gave me a blank on the left handlebar, so I might as well use it. The trouble comes in finding a properly oriented master cylinder that has the correct bore size. Harley specifies a 5/8″ bore for some applications, and a 9/16” bore for others using this same caliper. Without a good knowledge of what bikes would have such a piece, I began digging through my shed and found my way to a box of cast-off brake parts given to me by Jim Davis of Motomorphic fame. It was in that box that I struck gold: a clutch master and slave cylinder assembly from one of the Honda VTR1000F SuperHawks that had been through Jim’s hands. This assembly used a 14mm master—close enough to 9/16” that my rear brake hydraulics are now solved.

With rolling and stopping both handled, and a wait time ahead for free parts to be shipped and fabricated, I decided to mount the fuel tank and decide on a fender and seat solution.

The fuel tank install could not have been easier, since the tank was intended for this very frame. I did decide to relocate the mounting holes 1” lower, to add handlebar clearance.

The newly installed tank revealed that the handlebars would need to come up. I happened to have squirreled away a set of Rox risers, but while that should have been a quick and easy solution, it was not. The Husky triple trees had a Fast by Ferracci bar clamp assembly that wouldn’t work with the risers, so I replaced that assembly with a set of stock SV bar clamps from my deep catalog of cast-off parts—but they angle back the wrong way and don’t interface with the Husky triple so well. I did get it all assembled, but unhappy with the finished product, I decided I’d have to revisit the bar mounts later.

Another thing on the list was the rear fender. More than just dirt protection, the fender would be the luggage location as well as seat mount. I’d been eyeing a few designs, but the look that appealed to me most was a trailer fender: a simple, single 180-degree steel fender.

Such a thing should be easy to find, but local supply houses only stock plastic and aluminum units. I planned to do some welding on mine, so a heavy steel piece was required. Again, I turned to Craigslist and found a gentleman selling one for a whole $10.

In Petaluma.

I set out on a Saturday morning, hit a few local trailer repair places to see if a dented fender could be snagged, but no such luck. So I made the drive to Petaluma, handed the gentleman $10 and drove home with a rusty but straight trailer fender.

The drive home from Petaluma was full of phone calls, one of which spurred the fix for my handlebar clamp issue: Jim Davis came to the rescue by reminding me that DR650 bar clamps would likely interface correctly. I sourced a set for a whopping $20 from Hayward Cycle Salvage, and the bars are now properly risen!

Handlebars in place, I turned my attention back to fitting the rear fender. My $10 fender’s eight-inch width fit within the Harley frame rails with no alteration, but needed to lose four inches to satisfy my eye—quick work for my angle grinder and cut-off wheel. Simple angle iron brackets were welded into the frame, and my fender mount was done.

I’d initially planned to use a traditional chopper-style spring seat. The mounts on the frame were already present, after all. I went to Dirtbag alumnus Tony Spinks to inquire about his seating preferences, resigned to the likely necessity of dropping some coin here. Comfort is important, after all.

Tony’s advice was to avoid a spring seat at all costs, and his tales of pinched anatomy and discomfort that set in within minutes of riding sealed that decision for me. Back to Craigslist.

After a few days of relentless browsing, a stock Indian Scout seat caught my eye. I remembered riding the Scout and not hating the seat, and the seller was asking a reasonable $100 for it, so I responded. The seller was atypically easy to deal with for a Craigslister, and met me in Milpitas.

Duplicating the factory Scout seat mount took a little imagination and a trip to Ace Hardware: I repurposed a shaft collar and a button head Allen bolt to hold the butt bucket in place. Creative welding ensued, and I was even able to facilitate an adjustment to pull the seat into the contour of the frame/fender interface.

The last order of business was a question of taste: to sissy bar, or not to sissy bar. I know luggage will be something of a challenge on this bike, and a sissy bar offers a good place to anchor a bedroll. This thinking led to a phone call with my dad, who recommended I reinforce my rear fender struts and add at least a small bar to tie things against.

He suggested a design from his younger days, which involved 1/2″ round stock, heated and bent into a coil, similar to a safety pin. His preferred shaping buck was a starter motor—apparently he kept several on shelves in his chopper-building heyday.

I don’t keep many starters on my shelves, and if I did save one, I don’t think I’d want to subject it to an oxy-acetylene torch flame. But I did have an argon bottle lid that looked to be a good size for my coil, so I marked the center of my bar, clamped the bottle lid in my vice, and lit my torch.

There are few fabrication activities that are as much fun as heating and shaping metal like this. Using a rosebud tip on a torch feels incredibly dangerous and outdated at this point—I rarely fire up my torch set anymore, as most cutting is handled by abrasives or plasma. I do my welding with MIG or TIG. The oxy-acetylene rig exists only to make metal red hot and bendable, and it’s extremely good at that task.

Ten minutes later, I had a proper safety pin sissy bar, ready to be welded to the rear of the bike. I stitched more 1/2″ round bar to my fender struts, and  made sleeves to attach the new addition.

So at this point, Project SnoMoChop rolls, steers, stops, and has a place to sit. I have in my possession a set of fixtures made to install a similar drivetrain into a Mazda Miata (don’t ask), and the correct sprockets to hypothetically gear the bike to amble along at seventy miles per hour. The majority of the remaining tasks are manageable on the surface, but with just over two weeks remaining until the 2018 Dirtbag Challenge, I am dreading the creation of my exhaust system and becoming more worried about the ever-decreasing area where I will need to place footrests.

Stay tuned

→ Check out part 4 of the SnoMoChop saga here.