Gear ratio for YS 91

[vinver]

Hi all,
I read on Todd Bennett's website that the YS 91 with hatori SB-16Fh pipe works best at a ratio of 8.45:1, with 90 tooth gear that works out to 10.65 teeth on pinion. Hmm..
With the 12 tooth gear (7.5:1) would it be a better option to go with the 11 tooth pinion instead to optimize the gear ratio (8.181818...:1) :?:
How hard is it to just replace the pinion? What are others with YS engine running for pinion gear ratio?
Cheers,
Vincent

[cbergen]

The pinion is threaded into the clutch bell, and Red loctite was used when installed.

You can replace the pinion, however you must be careful not to shatter the pinion if you grab it with pliers, and when installing the new one, you'll want to make sure that it runs true with the clutch bell.

Or you can send it to us, we'll replace it for the cost of the pinion and shipping.

Keep in mind that Todd's recommended ratio may be on another machine, with different blades, head, weight, etc, etc.

I would try it first as it is, if you feel the need for a change, then send it off, or get another clutch bell with the 11 tooth pinion and do a side by side comparison for your style of flying.