YS50ST from OS50Hyper

[tec548]

Guys maybe you can help me out here. First here are the basics. I have her set-up with +13/-13/8/8/8/8 and run 2150hs in I2 with a GV-1 and Radix SB600 blades.

I have been running a OS50 Hyper in my 600N since May. I have been very happy with it and it makes very good power with the Align pipe on it. I run about 185F on the head and the engine seems to be very happy there. I have about 40 gallons on my 2 Hypers since May (many rear bearings too). Here's my problem. My buddy got a YS50ST and it was sreaming so I decieded to get one too. After all I have the YS91SR on my N9 and I absolutely love the engine.... mondo power. So, I really want to like my new YS50ST but after about 3 gallons it just is not making the power the OS does... and not even close to tell the truth. I'm running everything exactly the same and this motor just bogs and bogs then bogs some more. I'm running a head temp of about 180F and the main needle is at -2 clicks from 1.5 turns out. I have heard the the YS50 needs more heat to make power... is this so? Should I lean her out some more? What temp should I go to? I have heard the this engine likes to run 210~220F. Like I said I really want to like this engine but it's nothing like the 91 so far. Any comments, suggestions, ideas, anything will help.

Joel

[WayneBrown]

YS historically wants to run richer on the top. Myself and others have found that you need to pay particular attention to the idle tune as well as the high end as there is not a mid-range adjustment like on the 90's. Performance will suffer at flying RPM.
Idle: Lean enough to pinch, 5+ seconds before RPM increase and lean out. When you hit hold, it should not 'ping' on decelleration.
Main: Tune like OS, then a 1/2 turn richer. :)
Really, it may not be quite 1/2 turn, but if it ain't smokin' it won't make power. When You tune your OS's, you are listening to it, if you hear the same with a YS you are too lean.
YS is torque more than RPM..