See,... theres people who will run them till they break, then they know they need something done because it went boom, or you can keep them fresh. Sorry, but rings and pistons in a 2 stroke snowmobile of any brand will not be within spec at 11,000 miles no matter what oil you run!! It may still run fine to you the same owner of it since new, I dont argue that, these yamahas are great about giving you trouble free service but its not running the way it did when it was new! I would be willing to bet you the sides of your pistons were very dark brown and black all the way to the bottom of the side of the skirt, this is blow by!! this cant be done with a compression tester, see you can build compression, but how long can you hold onto the compression is the real task in a 2 stroke.
I fixed a srx last year that was the cleanest sled you could ever possibly find, I think the guy kept it in his living room..., anyways, at 6600 miles all 3 pistons were way under spec, yamalube used its whole life. Sure it started and ran fine, but it wasnt making all the power it used to!! The thing is if it would have had the piston rings changed just 1 time in the 6600 miles, it wouldnt have gotten to the point of letting the piston rock back and forth and wear the skirt from instability. The stock yamaha srx/viper pistons are about the best out there, a powder forged unit that runs a nice tight skirt to wall clearance, this improves sealing and stability, but once the rings get tired, it lets it rock back and forth and this leads to skirt wear and blowby. I dont think people understand what it is that drives a 2 stroke engine, its the piston/rings!! Theres no camshaft, valves, oilpump,etc. Ring seal and piston stability is crucial in a 2 stroke, its how all the power is moved around in the engine, and it is what the deciding factor is on how quickly and efficently it can be moved, sloppy rings and pistons contaminate the fresh fuel/air mix in the crankcase with burnt fuel/air charge that seeps by the rings into the crankcase below instead of being evacuated out of the engine, this in turn heats up your fresh mixture and this makes less power. heat is the number one enemy of a 2 stroke sled, the warmer the engine, the richer it is, the power drops off!
The reason there isnt 2 stroke cars out there is because although a 2 stroke engine makes more power then a 4 stroke does with less weight, it cant be made to give suitable service life without piston /ring service!!
Like I said, some people will run them till they break, thats fine its a free world, you have to make your own decisions, but if you want your machine to stay in tip top running shape, you cant ignore the rings and pistons...its like not ever changing the oil in your car till 50,000 miles! sure it will run fine, but its not going to make the power it should from the contaminates in the oil which in turn effect the way the engine makes power overall. Its your engine and what and how you maintain it is entirely up to you, I am just trying to explain why you should maintain it, at least you have the facts and other differning opinions...........what you do is your decision.
