Gypsy,
Take the time to pick up the phone and call one of the Hill brothers over at Northern Power Sports in Fairbanks. They are the Yamaha/Arctic Cat dealer there. They ride, born and raised in Fbks. We both know they get much colder than we do on the coast. If there are any real issues with the 4s starting, a cut off where they need heat assist, etc, they FOR SURE will know about it since they deal with a loyal customer base.
i gotta agree with Yellowknife on there ain't no way in hell a 4s motor is going to start at minus 50 unassisted. You would be hard pressed to get a 2s going at those temps.
i do know this: my 4s atvs will go reluctantly at minus 10 or 15, but that minus 20 really makes a difference.
i also know my chevy pickup, fuel injected and relatively new, hinges on the -20 go/no go point as well. I usually plug it in anything below zero, but sometimes I forget and i have had to crank it to go to work at minus 20.
my thoughts on 4s is they should all have preheat at that point, trucks, atvs, and snowmachines as well. even with a low viscosity synthetic oil, there are just so many more moving parts that just don't want to turn at those temps. cranking speed is a big factor in start or no start conditions, whether its a atv/truck/snowmachine, and you just cannot get it with a tight motor in real cold temps.
most definitely, i would install the largest battery i could get in your sled. however much room you have, even if you have to revamp the brackets and tie downs, go with a larger capacity battery. i'm not talking a truck battery, but there are a lot of them out there for larger atvs and such that would give you more cranking speed and cranking capacity. you want to go with the largest ampere (amp hour) rating you can, and the largest physical size. relate it to ( no doubt you have experienced it first had) to cranking a truck and it will "almost" start, but when you have a friend jump it with his truck, it turns over faster and starts.
there is no much parasitic loss in cranking a 4s over a 2s its not funny. turning over the top end through the cam gear, chain, the cam itself, overcoming valve spring tensions, plus an oil pump, the crankshaft to primary clutch gear reduction unit...that is a huge tax on that little battery,
PLUS, its trying to maintain that 12 and a half volts the entire electrical system needs (sensors, ignition, ecu, etc) to run correctly.
those of us who have lived in arctic conditions for as long as we have know a thing or two about cold weather starting vehicles. i don't think Yamaha or any of them really have a clue due to no first hand experience. they might do "testing" for a week at times, but that really is not the same.
Give NPS a call and see what they have to say.
I don't get why your sled would not start after being shut down only an hour...that to me spells something else. But getting it fired first thing in the morning, for a test, i would take a known charged large battery, such as out of a truck, hook it right to your sled battery with jumper cables, then try to crank the sled up. you will have a faster cranking speed, and i would be very curious to know if this makes a difference.
Another thing I would do is put a digital volt meter (Fluke) on your battery first thing on a cold morning, see what static voltage you have. Don't use a cheap meter! Borrow a good one from a friend if you need. If its anything less than 12.3 or so, that really isn't enough. Then, crank the motor while watching the battery voltage on the meter. If it goes anywhere to the 11 range, no good.
A "12 volt" battery is marginal if it reads anything less than 12.5 volts in its ability to start anything. At 12.1 or 12.2 volts, its basically dead and needs a charge.
I've been a mechanic here for 30 years, on everything from outboards to atvs, snowmachines, trucks, and diesels.
