The final time we heard from Sean Skinner, he’d simply constructed a Yamaha XS650-powered reproduction of the Nineteen Sixties Schwinn Stingray Orange Krate bicycle. The oddball creation was a far cry from the tidy restomods that his store, MotoRelic, is greatest recognized for—however it was no much less superior.
Once that bike was bought, Sean had an itch to unleash his inside baby once more, so he got down to construct one thing even wackier. Best described as an “overgrown mini-bike,” Sean’s new whip includes a bespoke body and a two-stroke Yamaha snowmobile engine. Yes, you learn that proper.
Inspiration for the construct got here from Sean’s youth. “As a kid, mini-bikes were always in the stable,” he tells us. “Either a Honda Mini Trail or some 5 hp, friction brake death trap.”
When this nostalgia collided with a sudden curiosity in classic air-cooled snowmobiles, Sean figured that utilizing a standard bike engine can be too straightforward. So he scoured his native classifieds for a 1982 Yamaha SRV 540 unit—a compact two-stroke, pull-start snowmobile engine, with nearly 60 hp on supply. He quickly discovered a whole donor sled, yanked the motor out, and bought the remainder of it to recoup a few of his price range.
The engine was rebuilt with new bearings, pistons, and rings, and a contemporary bore. In snowmobile kind, the SRV 540 makes use of a CVT system to switch energy to the observe—however this construct known as for a standard handbook transmission. So Sean needed to devise a workaround.
“On the crank, there’s a nice tapered shaft to attach a Belt Drives, Ltd. belt drive pulley to,” he tells us. “I had my friend at RTD FAB make an adapter to mate the two together perfectly. Then, for transferring power to the rear wheel, I used a Harley five-speed transmission that was donated to the project (thanks, Dave).”
Sean disassembled the transmission, rebuilt it, and reduce off something that wasn’t wanted, together with components regarding the Harley’s starter. All of the engine and transmission covers have been then both vapor honed or coated in a textured black end, leaving the drivetrain trying nearly as good as new.
Once all the pieces was again collectively, Sean fabricated a fixture to carry the engine, belt drive, and transmission collectively, after which welded that fixture to his body jig. That helped him preserve all the pieces aligned, whereas he TIG-welded the body tubes collectively and added the motor and transmission mounts.
It’s clear that Sean agonized over getting the strains of the body proper, as a result of this not-so-mini-bike is inch good. A ton of labor went into the entrance finish too, the place he narrowed, flipped round, and mounted the forks from Honda’s quirky ATC200 three-wheeler. Jeremy at LC Fabrications lent a hand too, by fabricating a decrease yoke to assist the ATC200 forks play good with the Yamaha RD350 steering neck that Sean had used.
“I thought way too long on what to do for the front end,” Sean admits. “Most mini bikes have a continuous ‘fork’ from axle to handlebars. I really wanted that look, but coming up with a riser-less setup was interesting.”
“I ended up with a design similar to how a mirror threads onto a motorcycle. The lower parts are threaded into the fork tubes through the upper triple, and tightened into position with lock nuts. The upper part then bolts on to those, creating a truly one-of-a-kind front end.”
For the wheels, a set of classic 16” Henry Abe mags have been sourced and slapped on. The entrance wheel is a Harley-specific half, whereas the rear is supposed for the Honda CB750 and is put in with {custom} spacers. Pirelli MT60RS tires full the look whereas providing a smidgen of off-road functionality.
“I have to say that I really lucked out, with the engine and trans balance center lining up perfectly with the center of the rear tire,” Sean tells us. “This made the drive chain and primary belt alignment incredibly easy, and it made the bike very balanced. Take the victories where you can!”
The bike has only one brake; a Honda CB750F Super Sport setup on the rear wheel, linked to a late-model Harley Sportster grasp cylinder. “I like it because it has a built-in return spring and lever stop,” Sean provides. “That made it super easy to fab up everything.”
The foot controls are all handmade components, whereas the foot pegs have been provided by Johnson Engineering. They’re immediately mounted to tabs that Sean welded on to his {custom} body.
With the bike now a rolling chassis, Sean turned his consideration to the bodywork. A custom-made aluminum gasoline tank sits up high, with a bit of it extending beneath the seat to maximise the bike’s vary. Wes at Counterbalance Cycles added a slick black leather-based cowl to the seat, matching the stitching sample to the tread sample of the tires at Sean’s request.
Finishing the bike off is an exhaust system that features handmade sections, items of an enlargement chamber from a Polaris, and an HVC Cycles muffler. “This engine was designed by Yamaha to have a two-into-one intake and exhaust,” he explains. “I had to extend the intake to clear the trans and make the expansion chamber completely from scratch—something I have never done.”
Dubbed the ‘Green Monster,’ Sean’s outsized mini-bike wears a shiny lime powder coating on its body, handlebars, and rear fender, black Cerakote on the exhaust, and a touch of darkish bronze on the wheel. (Right-A-Way Powder was accountable for all the powder coating work.)
And sure, the Green Monster is as bonkers to experience because it seems to be. “Pull-starting a motorcycle is not something that’s normally done,” says Sean. “Luckily the 540 two-stroke is very easy to start and doesn’t require the strength of a rugby player.”
“This bike is about how you would expect—obnoxious on so many levels. From the exhaust crackle and smoke to the open primary dry clutch noises, to the hand-numbing vibrations at full RPM. It’s definitely a handful!”
MotoRelic | Instagram | Images by Jonathan Thorpe
Source: www.bikeexif.com