Chrysler Sno-Runner: Restoration Complete!
You may recall our initial story about finding a vintage snow cycle called the Chrysler Sno-Runner. Since then, the restoration in preparation for fending off the winter doldrums here in Wisconsin has moved ahead.
First was to check the specifications on the machine–once some of its history was uncovered. Turns out the Sno-Runner was originally conceived for the U.S. Marine Corps back in the mid-seventies, but after field testing of prototypes, the Corps decided the Sno-Runner was 4F.
Not inclined to waste its development time, since tooling and manufacturing infrastructure already in place for the machine, Chrysler decided to take it to the consumer market in 1979. By 1982, Chrysler’s financial situation was such that the Sno-Runner had to go, so all the machines and parts were sold off to a liquidator.
The Sno-Runner that we have was in good condition overall, with good compression and an engine that turns free and has a bright, blue/white spark at the plug. But as disassembly went on, it was in dire need of work in some areas, most notably a badly corroded and damaged final drive chain.
The final drive chain is housed under a long plastic cover. Even removing the old drive chain proved to be a multi-day task. Corrosion had locked the links into a solid bar and where it turned around the sprockets, it was not only frozen in a curve, it was bonded to the sprockets, as well. After backing the chain tension adjuster off (fortunately not locked up) and soaking the whole chain repeatedly with PB Blaster penetrant, it finally limbered the links up enough to allow it to be removed.
Next the primary drive chain and centrifugal clutch were checked. The clutch shoes appeared mobile, not very badly worn, and the housing had only mild surface corrosion in spots. The primary drive chain had little corrosion, but was very loose, and with no automatic tensioner and way to adjust the tension, it was also very worn. With the plan requiring replacement of the entire final drive chain, it made no sense to rely on a badly worn primary drive chain, so that was replaced.
The muffler and heat shields were covered with surface rust, but not corroded through anywhere. Removing the rust, cleaning and repainting those components was all that was necessary. In some instances, new washers and fasteners were in order due to rust.
The plastic final drive chain cover and primary drive chain covers were both cracked. Using an old trick I learned fixing plastic snowmobile hoods years ago, I was able to weld the cracks on the inside surface using a soldering iron. The crack on the primary cover was minor, so that was all that was required, but the crack on the track chain cover was 17-inches long, so that would need reinforcement. The welding process causes a rough plastic surface, so it provides excellent anchoring for a layer of J-B Weld layered over the top of the plastic weld.
The skis were originally black plastic reinforced with fiberglass, but when acquired, they had faded to a dull, uneven gray. Using a product called “Restore Black,” the original black surface color was restored with four coats.
The throttle cable had developed a minor angular kink right at the point where the cable exits the twist grip. Knowing that a kink like that is a stress concentrator that could lead the cable to fail, I moved the cable so it would exit straight down instead of at an angle. I also added a stiff piece of fuel line tubing that fit snugly around the cable and ferrule at the twist grip to keep the kink straight and prevent it from re-kinking.
The brake is operated by a lever on the left handlebar, which acts through a band around the clutch housing. Everything was in working order, and all that was required was some cable lubing.
There’s no suspension, but the seat is massively padded; better than most motorcycle seats you may find. It has the original seat cover bearing the “Chrysler” name on it.
Transmission is a single-speed with a centrifugal clutch driving a #35 standard implement grade roller chain to the drive track chain. There isn’t a track in the snowmobile sense of the word; not a rubber one, anyway. Instead, there is a #35 roller chain with 21 paddle-track style polypropylene cleats spot welded on.
This unique drive system as well as the carburetor, kill switch, dimmer switch and other OEM parts replaced is still available online as new old stock (NOS) from the nice folks at Sno-Runner. Delivery was fast and accurate and each of the parts included easy-to-follow installation instructions.
The powerplant is a Chrysler Marine “Power Bee” 134cc loop-charged two-stroke single cylinder with CD ignition fed by a Tillotson 320A carburetor. The standard version was a claimed 7 horsepower, while the high-performance version was claimed to put out about 10 horsepower. Starting is with manual choke and recoil. There’s a 90w alternator to power the high-low sealed beam headlight and taillight that includes a stoplight.
The fuel is a manual-mix; no oil injection fed from a 1.3 gallon tank that is in the main top tube of the all-aluminum frame. The fuel line has a quick-disconnect similar to that used on compressor air hoses to allow the engine/transmission unit to be separated from the seat and frame top-tube assembly that houses the fuel tank.
In trying to get the engine back in tune, I could get it to stay running, but only with the choke fully on. Worse, the more fuel that went through the tiny Tillotson carb, the more leakage occurred from the carburetor body. I tried Yamaha carburetor cleaner to de-varnish the tiny passages in the carb and get it to run normally without the choke on, but to no avail.
Since these carbs have flexible diaphragms in them that can be subject to tearing, stretching and just plain failure after so many years. There may be problems with the fuel passages that wouldn’t be resolved even with a good cleaning, prompting me to forget about rebuilding the old carburetor and just buying a new unit. Since the purchase price was only $125, I thought that would be money well spent, particularly in terms of long-term service compared to the old carb rebuilt.
On the day after Christmas, 2016, the sun came out and temperatures outside soared to 45 degrees hereabouts in Wisconsin. This would be my best chance to do the work needed to get the Sno-Runner back out on the snow without having my flesh freeze to the wrenches, so out to the garage I went. The first project was to replace the damaged headlight high/low beam dimmer switch.
On the instances when I could get the engine running, I was able to determine that the headlight and tail/brake lights work, so all I needed to do was order a new headlight dimmer switch. That installation went without a hitch—everything is out in the open and easy to work on—just a matter of managing not to mess up the connections.
The toggle kill switch popped apart during the early part of the restoration work and would not stay intact when reassembled. Since a heavier duty version was available for that, I ordered one of those, too. That installation was an easy matter of cutting and reconnecting the wires, again all out in the open for easy access.
Carburetor replacement is a little more involved with some limited access space fasteners, but what I thought might be a hassle proved not to be thanks to a slick design of the throttle linkage unit. Chrysler designed the air intake horn as part of a single-molded unit that also encloses the end of the throttle cable and return spring mechanism, helping to prevent snow and ice from building up on the throttle plate end, which in my experience with snowmobiles tends to be the number one cause of stuck throttles.
The big benefit of this unit construction throttle mechanism design is that by taking out a total of six screws, the throttle cable end assembly comes off without having to actually undo the throttle cable ferrule and return spring—a major source of headaches to readjust after reassembly on some other machines I’ve worked on.
The new Tillotson HL320A carb bolted right up; the throttle mechanism reassembly went smoothly and that part of the project took about an hour. A dab of thread locker on all fasteners and the installation job was done. Then it was time to set the high and low speed jets.
The instructions that came with the carburetor say to set the high and low speed jets at 1 1/8 turns out from the seat for initial start-up. The instructions indicate this is a “rich” setting that will need some readjustment once in use. That setting is probably specified with a brand-new, never-been-run engine in mind to prevent engine seizure. Nevertheless, I used that setting. After connecting the fuel line, opening the fuel tank vent and setting the choke, it was time to give the starter a crank.
In my case, with a well broken-in engine, those settings proved to be way too rich as the thing flooded immediately with my first starting attempts. The instructions indicated the average jet setting in operation is actually about ¾ of a turn out from the seat, so after a few incremental tries at leaning out the mixture, I decided to just go with that and voila; after drying the plug and cranking three times more, the little Power Bee motor spun to life and kept running! It smoked a lot at first, but soon, it was running smoothly and nearly smoke-free.
Much of our recent snow had melted and what was left was wet, heavy slop about the consistency of wet cement. It was not really good enough to try reaching the local snowmobile trail system that runs nearby, but it was enough to let me do a few very short runs in my back yard, just to verify that the clutch, brakes, engine, drive system, track and so on would actually function and move the machine with my body weight aboard.
Result: yes! The Sno-Runner is running, functional in all aspects and ready for a try on the snow—when it arrives again. Oh, yes, and of course it’s ready also for me to have to pay the registration and trail use fees. All told, not including those fees and assuming my time has absolutely no value where such restorations are concerned, parts and paint required for the restoration came to about $450. Not a bad investment for on-going access to Chrysler’s cryotherapy for a motorcyclist with the winter doldrums!
Watch Ultimate Motorcycling for a further update on how we do once some real snow and better riding conditions return and we’ll have a full road—er, trail—test report.