I took apart my stepfather yami enticer 2 410cc fan engine for a big tune up at 17500km...
One thing I notice...is that the oil injection tubes (2) that are coming out of the pump are not going in the engine but they both go in the gas line near the gas pump. So this mean that it does premix oil in gas before it goes in the carb. Are all the yami the same?? Is this why those engine are super reliable?? Could this setup be done on other sled without blowing an engine?? If anyone knows something on it tell me please I want to know more...
;)

This is not a good setup in my opinion.If your out on a lake and pin the throttle you have to burn all the gas in the carburetors and lines back to the point of where the oil enters before you get increased oil from the pump.Its like a big delay from the oil pump. Also then when you let off you momentarily have too much oil for a while until you burn all that fuel up.Skidoo's have the little nozzles going right into the crankcase in front of the carbs so the second you get on the gas your getting more or less oil when you need it.I'm not sure how the other brands do it but I think its something similiar to Ski-Doo.I don't think yammie is even using this anymore.

I also thought about this delay....But if you could see the piston/cylinder condition...I could clean them and sell them to you as new one...amazing how the condition of the engine is after 17500km...MAybe the oil is doing a better job when premix in the engine....but for the delay?? mystery...Still waiting a good answer....

That is an arrangement which is common on many outboard motors even today. And it works well on outboards. (The funny thing is, Yamaha is not one of the makers who does it that way. They inject right into the case.) The big difference with an outboard is that they tend to be run at a more even rpm so the mix isn't and doesn't need to be varied like it does with a motor that varies in speed like a snowmachine. Obviously it has worked well in that motor in the way it has been used. It may not be such a good thing for a motor that is being abused. You could also read that as "raced," which is, IMO, a form of abuse of an engine. I'm not badmouthing people who race - it's their money - they can always make more and the industry loves to build more for them!

I suspect this is something that ended, not so much because it didn't work, but maybe because it may have appeared to be inferior to the more direct injection. I know there are currently outboard people who wonder if injecting into the fuel is as good as direct. History doesn't seem to satisfy them as much as theory.