As far as I can tell, there are two oil injection systems that were used on the M/NS90A. The earlier system is what I'm used to seeing on snowmobiles - The oil injection pump outputs to three lines. Each line feeds into each individual cylinder, plugging in above the reeds and injects oil into the inlets, downstream of the carbs. However, it looks like this system was superseded with a much simpler system whereby the oil injection pump outputs through one line that is teed into the main fuel feed line to the carbs. I believe this is called "automixing".
I just bought a NS90A with the early system, and it came with a parts motor that has the newer style system. Are there any concerns with the early system? Both systems appear to oil very little at idle (120 to 1 is the spec I have seen). I'd imagine the early system would react more quickly if you went to WOT, but it is more complex with a possibility of plugging etc. If there are reliability concerns I might swap the systems out.
Thanks!
I just bought a NS90A with the early system, and it came with a parts motor that has the newer style system. Are there any concerns with the early system? Both systems appear to oil very little at idle (120 to 1 is the spec I have seen). I'd imagine the early system would react more quickly if you went to WOT, but it is more complex with a possibility of plugging etc. If there are reliability concerns I might swap the systems out.
Thanks!