View Full Version : ys91 tuning

04-13-2004, 01:58 PM
I aquired a ys91 second hand and it has approx 4-5 gallons through it running on a mp2 in a raptor 90(8.45 ratio) Im having some issues tuneing it and wondered if anyone can share their needle settings. If your from Ohio...all the better!!!


04-13-2004, 02:10 PM
Needle settings will vary according to atmospheric conditions.
Here is my settings using Cool Power 25% fuel with 17% HV oil.
Also I have a Viperhead on the motor which allows the needles to be a couple of clicks leaner.
I am using Hatori SB 16 and 7.75 to 1 ratio in Tempest.

Mid Range needle ( long one) 1 3/8 turns open from fully closed
High Needle ( short one) 3/4 turn open from fully closed
Low end The needle is just about flush with carb barrel. I didn't mess with it, but I believe it is like 1.5 turns out from fully closed.