Uhhh... Well I think you wanted a 3 wheeled bike for stability right? In snowy conditions? Erm... Well a v twin of that magnitude should probably be used in something way beefier than a bike frame, and lower, and closer to the middle. Oh and not to mention going 100mph is never a good idea in the snow or anywhere except for Germany...
Id settle for the 79cc,or take a small hop up and find a Honda gx100 engine clone, it's 98cc, but still manageable on a bicycle and the bike will hold up (that v-twin is over a hundred f***ing pounds! You. And the motor will spell flat tire city if the steel tubes don't fold like cooked spaghetti first haha but I like the enthusiasm you've got for it I'll tell you that much.)
Durability often comes not from the type of parts, but the ability to separate them from the outside world, a bearing exposed to the dirt and water will be destroyed and pulverized in no time, but put 2 rubber seals on it and the life expectancy will be multiplied a hundred fold.
Then say on the jackshaft, use not just 2 bearings as the load handlers, but 4 very well aligned bearings, which doesn't just halve the load on the original bearings, but does as much as 1/8th'ing the load, because the leverage forces and twist forces are removed from the ends of the shaft, and they become linear forces across 2 bearings AND the shaft, that means that the balls in the bearings are distributing the pull force more evenly between each other, giving force loads across more than half the bearing vs roughly a quarter, that's half the force, halved twice, as each bearing only has to hold half the weight, and half the leverage forces because now the shaft supports itself, or 1/8th for those of you counting at home.
Then look at chain options, there's #41 chain that costs $15 for 10 feet, or $25 for 3 feet, the difference in quality really is amazing as soon as you hold actual quality parts in your hand. Ask the go kart people, they know what I'm talking about here.
Then one of the biggest killers is lack of alignment, you can line up sprockets by eye and be just mm or 2 off and the properly fitting chain will eat its way through one, the other, or both, including itself, with time, bigger forces, bigger teeth, bigger bites, less drivetrain faster. Make sure you align align align, it's seriously important for longevity. A 11 speed bike chain used on a single speed bike, properly aligned, will take a serious beating of use a lot longer than the same chain being used lighter on a multi speed hub, the chain has to be misaligned to run on it, and that just kills it. I have my chains, with an internally geared hub, aligned perfectly, being internal means no external shifts, so my alignment remained constant, I have the same chain since November, always riding, and I only lubed it once, when I installed it, with wax (my wax is a rather special formulation, it's become tacky with time but it's still very much there, but I will also admit with the fuel leak here and there, the chains might be getting free clean lube every time I take it out, so it ends up the detergents are just cleaning and relubing my chains indefinitely, I'll put it down as a win in any case.)
Which is third on the list, lube it up baby, keep the bearings greased, small engines generally get a change every 100 hours, make sure the chains are PROPERLY lubricated, which means no effing wd-40 or household cooking oil!
A small trick I used on my jackshaft is I noticed when I took it apart long ago, the bearings begin to eat into the shaft, perhaps not eat but wear, it just shows the steel is softer than the bearing race, when I replaced it I heated it up nice red hot where the bearings would rest on the keyed shaft, then dropped it in used motor oil to harden and temper the steel, it prevents the wear from happening easily if at all, also makes it easy to remove the shaft from the bearing, and most importantly keeps the shaft rotating along its center rather than just a hair off center, which at those speeds and forces just a tiny bit is actually a lot, which ends up ruining the bearings, giving play, which helps the sprockets and chain wear faster.
Erm... Well yeah that's about it, but if you put a v-twin in a 3 wheeled bicyle please get a friend to video tape you breaking the sound barrier along with probably a few laws, a car chase would be nice too, don't wear a helmet so the police won't try to run you off the road so much, thanks!
