FC350 Motor Mount Bolt

If you remove that bolt (or the other one), your engine mount turns into a linkage rather than a proper mount. That will allow it to rotate and the whole chassis will flex more front to back, which should add comfort, and a touch more flex side to side, which should hurt cornering precision, but may help bump absorption when laid over in the corner. It's really not the right way to do it, and I definitely wouldn't recommend it as a permanent thing, but won't really hurt for a quick feel check for a lap or two. You could also remove one engine mount entirely and leave the other as-is for a test too.

If you like it better that way (or with the bolt removed), then you'll probably like a "softer" aftermarket mount. Note the improvements, if any, and in which direction they are (cornering, front to back, chop, etc.), then look at aftermarket mounts and see if what they've done makes sense from a stiffness change perspective in the direction you're interested. Most of them put a big hole in the middle, which will allow more flex side to side and just a little more front to back. Them adding a big hole likely won't change as much as removing one mount entirely or removing one bolt, though. I've yet to see an aftermarket mount company differentiate stiffness levels by direction, which is unfortunate. I have seen some factory bikes with interesting mounts that look like they though about directional stiffness, though. But that doesn't help anyone else much, unfortunately!

Yes, get a good baseline riding as-is, then switch it up. But do it before you're tired at the end of the day too. Back to back to back will give a good impression (stock, change, then stock again).

PLAY WITH DIFFERENT TORQUE SETTINGS

Please don't do this, you're much better off changing the mounts themselves to actually get a measurable difference.  A bolted joint should be just that, a bolted joint, not a slip joint that will act inconsistently and potentially cause premature wear.  You're not going to change the stiffness of the bolt by playing with torque specs, tension in a bolted joint like that should be within the elastic range of the bolt material, so where you are along the slope of that line is irrelevant from a stiffness standpoint.  

If you want, come up with a design for the hangers that you want to try and send them down to me, I might be able to mill them out for you depending on the geometry.  

Despite what Keefer and many others will say, there's no change in feel to be had from using a different torque setting on your engine mounts (or most anywhere else). You would have to go excessively tight to the point where the bolt breaks (obviously no good) or excessively loose to the point where things start slipping and sliding (and that's really bad too).

If you're just changing the torque 15% in one direction or another, there's simply no physical change happening to the bike. The engine mount is still stuck to the motor/frame and not moving, just like it was at the other torque value. And if there's no physical change, then there's nothing to feel. 

I think the point here is that lower torque means the mount can move, glide under the bolt head.

The holes in the mount is oversized which means if you torque it less, the mount should be able to move back and fwd under bolt head.

Not sure at what torque the bold head would fully fixate the mount or reduce it to very little.

The mount should absolutely not move, that would be a bad thing. It would be incredibly inconsistent, full of hysteresis, and wear away the parts pretty quickly. If it were meant to move, they would have rubber mounted the connection or come up with a much more consistent method to allow it to move back and forth consistently.

The bolt hole is elongated to allow for tolerance variation between the engine and frame pickup points, not to allow movement. There's a lot of parts between the engine mount location and the frame mount location (e.g. a lot of tolerances to stack up), some of that a welded assembly. There will be a good amount of variance bike to bike, and that elongated hole takes care of that so the mount still fits on the bike regardless of the tolerance stack ups. 

Further, a 5% change in torque (or something similar to that level), is lost in the uncertainty of friction and other variables. That 5% change in torque may not be any change at all, or even a change in the opposite direction, in relation to the bolted joint's resulting tension. Our blog post goes into a lot more details on this:

https://www.luxonmx.com/blog-luxon-bolt-torque-tension.html 

08 CRF manual, and other bikes I’ve owned, spec moly grease on engine hanger plates where it touches frame. I’m thinking that there must be some movement. 

Here's the 08 CRF manual I have and it doesn't specify anything special to those, just the torque. Maybe another bike has it? If so, it's likely to aide in settling everything under the initial torqueing and to keep things from galling up under any movement that may occur. Speaking of that, there certainly is movement in extreme situations (casing a big jump or similar), but it's very much not intentional.

Think about it this way: Let's just assume these are intended to move for argument's sake. In the case of a big hit that moves them in one direction, they won't "rebound" back to their initial position like your shock does as there's no force to reset it back. They will sit in this new position until another big hit comes along. If that big hit comes along in the exact opposite direction as the first (quite unlikely), then they'll move back the other way. But what if that big hit is in the same direction as before? They've likely already moved as much as they could in the earlier hit, so they won't move now. That would be super inconsistent from a feel perspective.