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Jul 28, 2023

Finishing the Snomo

By Fish Photography: Fish, Graf Holzfeuer & Angelica Rubalcaba Rider: Fish (duh)

By Fish Photography: Fish, Graf Holzfeuer & Angelica Rubalcaba Rider: Fish (duh)

Less than two weeks before the 2018 Dirtbag ride, the urgency of my situation hit me hard. I’d been working on Project SnoMoChop at a fairly relaxed pace until the looming deadline inconveniently coincided with an increased workload. With my time suddenly spread so thin, I could no longer document all my solutions to the unique problems of installing a snowmobile drivetrain in a motorcycle chassis. I wasn't even sure I could solve those problems in time for the ride.

The list of remaining problems was long. The powertrain was mocked up for fit on wooden blocks and shims in the chassis, but not mounted. I needed exhaust, an oil tank for the injection pump, an electrical system, and, and, and…

I started with the rear wheel—I could move forward from there once it was centered in the frame, but centering the late model wheel in the older frame presented a real challenge. I resorted to carpentry techniques to find measuring points: with the aid of a ten-foot stick of C-channel aluminum and a drywall square, I managed to confirm the squareness of the rear wheel relative to the frame.

The next step was prototyping my jackshaft bearing retainers. I’d planned to locate this part of the assembly on the factory transmission mount bosses which are in a flat plane—always a nice baseline. A little time with some cardboard and a tape measure informed me I had roughly 10" by 10" of space to work with. The snowmobile bearing retainers required roughly 4" of width to bolt in securely and I envisioned 2" gussets along the edges of my plate. I made a run to Pleasanton Steel and requested the cuts of 3/16" plate—another $27 from my budget to make locating the jackshaft easier.

The 4" plates were cut to height to keep the chain in-plane and hopefully safe from contact with the narrow frame or the ground. I tack welded them into place and slid the assembly in, only to find my sprocket was too far offset to the outside. I’d installed a 1/8″ spacer between the sprocket and rim to compensate for a difference in hub size, meaning I’d need to buy a new sprocket or open up the hole in my current one.

This is where having the right friends makes a difference: I called my friend Perry, who assisted me with the use of the boring bar setup on his milling machine. The newly-opened-up sprocket center fit perfectly on the rim and moved the chain inboard enough to clear the frame.

The next hurdle was finding a countershaft sprocket small enough to provide gear ratios low enough for the CVT (continuously variable transmission) to operate correctly. Harleys have some reduction in the primary drive system, so a 1:1 ratio in top gear usually requires something like a 53/22 tooth ratio. I needed something more like 53/11.

530 chain shares the same pitch as ANSI #50 industrial chain, so I sourced an eleven-tooth sprocket for the jackshaft from McMaster-Carr for $22, allowing me to mock up my locations. I had concerns about the durability of the industrial sprocket, as ANSI chains usually run at substantially slower speeds.

I made a call to a friend in Oregon, Shawn, who works for a gear and sprocket manufacturer. He penciled out a sprocket and flange design that fit the bill perfectly, which he donated to my project as payback for the times in our past when I’d helped recover his mud-stuck Jeep XJ.

Jackshaft and chain drive properly positioned, it was time to commit to an engine location. I’d planned to mount the engine low but realized the overall width would severely hinder ground clearance. Faced with the terrifying thought of going around corners slowly, I made brackets to raise the engine approximately 4" from the lower hoop, which seemed ok at first.

But then I noticed the exhaust outlet was too close to the front tire and the carbs were tight against the frame's center. I also had to consider the necessary center distance between the clutches while moving the engine around in the frame. The design of the jackshaft did allow me more than an inch of freedom in left/right location, but the exhaust and frame downtube dictated one location of the engine on that axis.

I called in more help, this time from my friend Scott—the inspiration for this build. Many years ago, Scott built a snowmobile-powered Mazda Miata for the 24 Hours of Lemons race series. The moderate success of that car gave me confidence that this project was mechanically possible, and Scott's knowledge would prove as invaluable as his improvised tools, including a fixture he’d made to set the clutch-to-engine distance.

Suddenly an intimidating task turned into quick clamping and more tack welds, and with that, the drivetrain was located.

My most dreaded task was next: building the exhaust. The sled had arrived at Casa de Pescado with a new stock pipe, giving me clean steel to work with, but making the expansion chamber fit the engine's new home in the Harley frame would require substantial recontouring.

The caveat here is that altering the pipe's diameter would affect the engine's state of tune, so I had to make endless "pie cuts," each halfway through the pipe in the axis of my desired bend, never opening one side up farther than I closed the other side.

This operation consumed three cut-off wheels on my angle grinder and took 14 hours. I made two complete cuts through the pipe where I re-clocked the bend, and then manipulated the rest of the pipe one cut at a time.

My efforts were rewarded with a job well… done. The pipe's outlet was firing directly where my right leg had planned to sit.

The tailpipe section was less daunting. I’d been hoarding Sportster exhausts on my shelf of random bits—stock Harley pipes are made of good quality steel with nice mandrel bends, so a bit of cutting and pasting allowed me to utilize the curves of these pipes to route the hot gasses down and away.

The exhaust re-complicated a previously-sorted problem: the fuel valve was smack in the middle of the exhaust system's path. I plugged that hole and welded a steel pipe bushing from my local hardware store into the opposite side and threaded the Harley fuel valve in. Some cast-off Volkswagen fuel line and a matching fuel filter finished the plumbing on that end.

I’d planned to use the stock Harley oil tank to store two-stroke oil for the injection system but had filled that space with the exhaust system and time was too tight to source a ready-made solution.

Thankfully, I had plenty of exhaust tubing lying around, so I shortened a piece of 4" tubing to fit into a small open space on the right, just behind the exhaust. I capped the ends and welded pipe thread bungs into it, and a steel pipe cap with a drilled vent hole answered the refilling question. With a capacity of 2 1/2 quarts, I wouldn't even need to carry extra oil for the weekend.

I’d been avoiding the wiring, mostly because I had little understanding of the snow machine's system. The ignition side is self-contained and required no alterations, but the lighting was a different story, using unrectified AC voltage regulated at twelve volts. LED bulbs or a battery were off the table, but I’ve always been a fan of magneto/battery-free ignition systems, so this part of the build satisfied one of my bucket list bike cravings.

There were three wires to work with. One is simply a wire to ground out the magneto, and the neutral and hot wires also carry the pulse signal for the tach, making that installation even easier. My finished product involved a tail/brake light, brake light switch, dual-beam headlight wired only on the low beam, and the factory tach tapped in. The lights are on when the engine is running, and off when the engine is off. Easy peasy.

The kill switch function was a bit foreign to me—the reverse of traditional ignition switches which disconnect power to shut the engine down. My initial plan was to just use a kill button, but the engine is quick to light off when warm and I wanted a way to keep the engine dead while I rotated it during clutch tuning and service.

The solution was literally in my own backyard: a TT-R125 parts bike with an intact key switch. The TT-R uses a magneto ignition, so connection was a snap—the switch bracket even bolted nicely to my bar clamp. The handlebar mounted kill switch came along as well—it almost like cheating.

I kept the headlight bracket simple, picking up the pinch bolts on the triple trees with vertical plates. Horizontal bars connected and gave me a place to bolt up a light… which I’d forgotten to find.

Another trip to Contra Costa Cycles netted not just any headlight, but a headlight I’d previously owned, from a crashed Dyna Fat Bob. I bought the light for my FXR prior to changing fork setups and gave it back to the shop in case anyone else could use it when I changed the front end. The light sat on the shelf across two years and an ownership change.

The new owner is at least a good guy, and he sold it back to me for the princely sum of $30. The dual lens setup fits well and compliments the wider Husky fork visually. Always better to be lucky than good.

My to-do list was shrinking, but I still needed to a place to put my feet and a sidestand. While visiting Contra Costa Cycles, I’d dug through the bins to procure a Shovelhead-style kickstand and spring. Mounting it took a little creativity: I used one of the left front floorboard holes and made a bracket to pick up two of the remaining three holes. Three out of four ain't bad, right?

I’d been hoarding an old set of highway pegs removed from a Sportster that passed through my shop. They’d started out as passenger pegs and were modified by the owner for highway peg use. I repurposed the complete assembly and nested it near the original forward floorboard mounts. With no foot controls, I resigned myself to forward feet and embraced the chopper lifestyle.

That brings us to Wednesday: time for a test ride. It was about 6:00 PM when I pulled the engine to life for my first test ride. The Dirtbag ride starts on Friday.

With an exposed spinning wheel of death directly behind my left heel, I gingerly twisted the throttle and waited for the clutch to engage. The tach climbed, but the bike sat still. 2,000 rpm… 2,500 rpm… 3,000… 3,500… at 4,000 rpm the bike started to roll.

I had expected some kind of startling jerk, but instead experienced a smooth take off. More throttle got me going faster with very little drama but a LOT of noise.

I understand the snow machine CVT in principal but was unprepared for how the experience translated to motorcycle form. Cruising down the street at no more than 30 mph, the engine wails at 4,500 rpm. A quick punch of the throttle spins it to 6,700 and the bike accelerates rapidly. Speed continues to increase, but the engine simply screams its 6,700 rpm song.

Not wanting to anger my neighbors (or catch my foot in the clutch assembly), I parked the bike and called it a night with less than 48 hours till the Dirtbag.

The bike rideable, I called in another favor: Scott, the original bad influence, came over and gave me crash course in snowmobile clutch tuning.

I won't bore you with all the details, but the gist of it is balancing the weights and spring in the engine-mounted drive clutch. You need enough weight so that the clutch closes up and moves the sled (bike) without bogging the engine. There's also a spring that is holding the clutch open, dictating the rpm at which the clutch ramps itself tighter, resulting in a larger effective diameter. There's another set of weights and a helical spring in the driven clutch, but the existing tuning in that side seemed to be well-suited for my application.

The drive clutch needed heavier weights and a lighter spring, both of which Scott had in his stash of SnoMoRacecar(?) parts. Our marginally scientific methods got the bike to take off gently at 3,000-ish rpm, settle in at low-load cruise at 5,500 rpm, and peak at the factory recommended 6,700 rpm.

The final detail: some kind of guard over the belt and clutch assembly, in case the belt breaks. More scrounging in my shop turned up some heavy expanded metal grating and left-over half-inch cold rolled steel rod from my sissy bar project.

I set out to bend and frame a guard. I got a rough idea done and called it a night. The finish work would have to wait until morning… the day of the Dirtbag ride.

I needed more steel rod to complete the guard protecting my left leg from the belt and clutch assembly, so instead of riding to the meetup point in SF, off to the hardware store I went, with a bonus visit to AAA to register the bike. SnoMoChop's registration was from 2015, a potential downer in case of interaction with law enforcement.

I returned home with tags and steel, and completed the guard around the time the rest of the Dirtbaggers were arriving in SF. I still hadn't packed, nor had I figured out how to secure my bedroll and belongings on the bike. I’d at least had the forethought to build a good tool and spare kit which fit nicely in a small-caliber ammo can.

Attaching the ammo can, a tent and dry bag to the bike was not as simple as I’d hoped. The flat fender surface and sissy bar seemed promising, but there was simply not enough horizontal area to accommodate the necessities for a weekend of chopper adventures. The final solution: a mix of camlock straps and a bungee cord, with my tent hooked to the sissy bar by the straps on the carrying bag. Not elegant, but effective.

Bike loaded, I tear out for San Francisco, to Poll's shop in the heart of Hunter's Point, one of the last ungentrified areas of SF. Commonly described as "raw" or "gritty," the area is made up of older houses bordering on industrial warehouses and a former Naval shipyard. The area has an elegant brutality to it, a perfect backdrop for the Dirtbag.

I knew I’d missed the big group departure, but fortunately Poll was still sorting his bike out so I decided to meet up with him instead of trying to catch the main group. But before I arrived, problem number one crept up: I lost both headlight bulbs. I had spares, but this being the second set of bulbs, I also had a suspicion that the system was over-voltaging and burning them out. Since it was daytime I declined to change them on the side of the road—I wouldn't be the first Dirtbagger riding with no lights.

I arrive Poll's shop just in time to join the celebration of Poll's bike roaring to life. This year he's decided to spruce up a neglected Kawasaki cruiser for the ride, giving his Copper Chopper a rest. We exchange quick greetings before Poll heads off on a test ride. I say hello to two others waiting for Poll. One of them is a man named Ed Gold, a fellow journalist, freelancing for the BBC. Ed takes a bit of interest in the SnoMoChop and we chat while Poll circles the block.

Before I can get into the finer details of my bike's CVT, Poll returns, proclaiming success. His bike publicly disagrees, however, spraying a mix of gasoline and oil out of the crankcase vent.

Just as you’d expect when a group of enthusiasts is confronted with a mechanical riddle, several theories are voiced. The large puddle of fluids is analyzed for smell and texture, and the group determines that the fuel tank had leaked a large portion of its contents into the crankcase via a sticking float in the carburetor. This theory is proven when the fuel level is found to be quite low and more than two gallons of fluid is drained from the crankcase.

Not to be discouraged, Poll fills the crankcase with fresh oil, tops off the gas, and starts his bike. It runs just like before, but without the pressurized stream of fluid exiting the breather hose. Success is again declared, and Poll heads into his shop to load up.

A short time later, after a bit of back and forth regarding directions our group of stragglers departs. It's dark by this point, and I am thankful for my now-functional headlights. I’m also more amused than I should be by the way the lights dim when the engine settles into idle, since the lack of battery means the voltage fluctuates with lower engine rpm.

The racket of the small group of bikes echoing off the industrial buildings combined with the smell of Poll's bike venting the last of its previous crankcase cocktail makes for a visceral experience… which lasts for approximately eight blocks.

Poll's bike is losing the front brake caliper and experiencing engine troubles. We turn around, back to the shop. I lose sight of Poll and beat him back to the shop.

When he finally emerges from the darkness, he's pushing the dead Kawasaki. He's not leaving tonight. I’m given the address of the campground in Jenner, where the rest of the group is waiting.

I’m asked to guide Ed along with me. He's riding a Suzuki TL1000R loaded with camping gear. We briefly discuss pace and his comfort with splitting lanes and depart, taking the direct route through San Francisco to get to 101 North. It's 5:30 PM—the evening commute gridlock and darkness have both settled in firmly.

I’m still quite amped up with the excitement of making it this far, and my pace reflects it. Every stop sign is an opportunity to launch a little harder and let the two-stroke sing a little longer. Ed and his TL follow as I confuse commuters with my mutated-leaf-blower-on-crack exhaust note, my GPS giving instructions in my ear as we criss-cross the city. By the time we hit the Golden Gate bridge, my cheeks hurt from smiling.

Crossing the bridge into Marin means a slightly more-open freeway and a carpool lane, but also a challenge: the SnoMoChop doesn't have a speedometer, and the tachometer doesn't correspond to any particular speed due to the variable gear ratio. This wasn't really a problem when there was traffic to keep pace with, but when the freeway opened up a bit, judging my speed was more difficult than I’d expected.

The rigid tail section makes things feel very fast, but I knew that would happen, so I compensated. We arrive at the campsite by 7:15 PM, meaning I actually overcompensated, but I’m okay with that.

When I say arrive, I really mean invade. The noise of the SnoMoChop cuts through the otherwise peaceful landscape, attracting the attention of the now-winding-down Dirtbags. The campsite location must remain a secret, but access included two miles of poor-condition gravel roads, one very narrow passage, and a quarter-mile of wet grass. Keeping the bike moving slowly on that wet grass means feathering the throttle and revving the engine like a frustrated GSXR bro splitting through narrow, gridlocked streets.

Embracing the obnoxious nature of my entrance, I ride right into the circle of my fellow Dirtbags gathered ‘round the campfire, their mouths agape with confusion and amusement.

This is my mission complete moment, my motivation for the build. From that point on I really could not have cared less if the SnoMoChop burst into flames or crumbled to bits.

If you read my story about last year's Dirtbag Challenge, you’ll have a good idea of the exploits that ensue over the next two days. We cover a couple-hundred miles of Sonoma and Napa counties, carve up Highway 29, challenge ourselves on the dirt roads of Knoxville, and have deep conversations over campfires. Yes, there's more to the story, but I’m hoping that keeping your curiosity intact might actually lead to you building a bike next year.

After three days of riding, we roll into the party with a few hundred spectators cheering our burnouts and hijinks. The curious stares and questions from onlookers were almost overwhelming. To most partygoers, the burnouts signified the start of the event, but for me, it was the end.

Poll has made threats now that the next Dirtbag won't have a party. Last year that didn't make sense to me, but it makes more sense now. As much I loved sharing the excitement of the SnoMoChop with everyone at the party, what stuck with me was the build process and the experiences on the road.

I’ll do my best to avoid romanticizing road trips and biker culture, but I must admit there's genuinely something to it all. Riding a homebuilt machine only really understood by you, the builder, means your motorcycle is an extension of yourself. Every mile takes on new meaning. Oh, and I won the Cleverest award!

I must thank my friends Scott DeWinter for the inspiration to build the SnoMoChop, Chris DeWinter at Big Boy Toys, who donated the sled to me via Scott, Perry Anderson for his help with the critical machining jobs that made the difference in the drive system fitting together, Editor Surj for giving me an outlet to document the chaos, and my fiancé Tam for keeping me sane while I put the mess together. This bike would not have happened without their help.

The bikes of the 2018 Dirtbag Challenge ran the gamut from radical to ridiculous. Veteran builder Justin Martens put together his version of a Yamaha XS650-powered super-ish moto. With an under-seat fuel tank and a handbuilt frame, the bike is the polar opposite to his rigid-frame build from last year, despite using the same engine.

That trick under-seat tank did come with some hiccups. The mounting bosses caused some cracking and eventually a large fuel leak Saturday afternoon. Justin borrowed a hydration bladder, filled it with gas, and rode the remaining two days with this temporary tank, helping to earn him the "coolest" trophy.

Another bike and builder that really stood out to me was Clyde Clyderson and his "Honduki," an unholy marriage of a Ducati Monster 900 and a Honda CB360 frame, with some bits of a Suzuki Savage thrown in. (The Harley front wheel didn't make it into the mashed-up name.)

Clyde was not just a first-time Dirtbagger, but a first-time welder and bike builder. An electrician by trade, Clyde learned how to weld by building his Honduki, thanks to some instruction from a friend and a little assistance with welding the aluminum parts. The courage to just dig in earned Clyde the "sketchiest" trophy.

Another first-time builder was Taylor Boyce, who also started with a Honda CL360. He built a rigid frame, but was not interested in sacrificing comfort for style, so he engineered a shock-mounted seat using one of the CL's discarded shocks.

Taylor's bike and riding earned the GULU or "LOON" award, which goes to the bike or rider with the most ridiculous situation going on. Taylor's unconventional bike and enthusiasm for riding the shit out of said bike certainly qualified as ridiculous.

In addition to the newcomers, there were repeat offenders who had upped their game. Matt (last name redacted) showed up with a Kawasaki ZR7-based build sporting a tasteful hardtail conversion and handmade coffin tank. His hardtail strut was sourced from a discarded staircase handrail. Square steel custom handlebars graced the top triple of a KLR front end.

Fish is Founder and President of the CityBike Society for the Preservation of Front Tires. He's already working on ideas for his 2019 Dirtbag Challenge, but let's be honest: it's gonna be hard to top the SnoMoChop. Stay tuned!

Check out more photos of Project SnoMoChop here.

AerostichAraibuildcampingchoppercustomDirtbag ChallengeHarley-DavidsonPolarisSnoMoChopsnowmobiletwo-strokewheelies

Exhausted just reading the article…Huge Project and the energy into it is Mega!

Thank you! It was a very fun undertaking. I do wish I had the time to document more of the build towards the end.

Wow, a really great job was done!

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