November thru February: Mostly overpriced bikes that the owner has been trying to sell since last fall, lots of months old listings, possibly willing to deal on prices still, or just as likely to give you the "Firm, if I don't get what I want for it I'll hold onto it until spring", even though it's still going to be 20% overpriced come spring. YMMV.
First February warm snap thru March: Tons of fresh listings of overpriced bikes that the sellers suddenly think will fetch top dollar because of spring fever. Some deals to be had if you can look through all the cruft.
Late March/spring weather actually arrives thru May: Peak listings, some sellers start to get desperate to sell their old ride to buy that new one they've drooling over. Sensible sellers start to lower their asking prices or become far more willing to deal on pricing. Still plenty of crackpots thinking that 10 year old beginner bike is worth $10K because it's "super customized".
May Thru August: Prices steady for the most part, still lots of buying/selling happening as the season is at it's peak. Lots of newbies coming onboard holding prices steady.
August & September: Prices start to sag as the end of the season is in sight. Still plenty of crazies out there who only rode to the nearest Tim Hortons twice all summer who now decide they don't really want a motorcycle anymore that decide their garage queen with 250KM/year on the odometer is still worth 99% of it's original price because "low mileage, mint condition bro".
October thru November: Lots of listings, people who simply don't want to bother with winterizing and storage are very willing to deal on price out of desperation to simply liquidate their bike...the smart ones know that after early November, it's a lost cause and they're going to own it until spring.
Repeat.