this is a fairly worn subject, but here goes:

it seems from what i read that 110/140 sumo tires is about right for this bike in terms of what it is able to push. Question is: is that true for the 351 also? Will it push 120/150 and/or is there anything to be gained (assuming it will clear the fork/swingarm)?

 

Some 150 rear tires will fit as people have done it before, but I don't think there is anything to gain traction wise and there will not be much room. The only reason I would put a 150 on is if the tire I was looking at didn't come in 140 size.

Acceptable power delivery is a personal thing and far to subjective. Some people think that even with a 351 the bike is gutless and others are fine with the stock 250 bore. Either displacement will move a 150 rear, but as I said there really isn't anything to be gained and the heavier the tire, the greater the effect it will have on the bikes performance.

 

I run a Distanzia 150/60 in the rear, plenty of room and I use the whole tire. The 120 in the front still has pretty big chicken strips tho. I need to make some footpeg sliders
I may go tubeless at some point to help counter the extra weight

 

 

110 vs 120 up front....pros/cons?

 

Id do the 110, Just cant seem to use all of the 120

 

Do u have any more pics of your bike showing front and maybe side?

 

 

Don't forget if you put SM rims on it will lower the bike quite a bit. Once I put my rims on I removed the lowering link and put the OEM link back on.
I'm assuming your SM rims are 17"?

 

Smalller tire less weight and less mass to rotate, narrower width will turn in quicker - quicker handling. One good reason to stay with the 110/140, the handling Kawasaki was going for and less power eaten up by mass.

Fat tires look cool to some, better traction if you are pushing 60 hp like a 450 MX based Supermoto.

With the same width rims, and it does take specific rims for given tire sizes, the wider the tire the more of a crown it will have and the smaller the footprint. Like a 3.00 rim will allow a bit flatter profile putting more rubber on the road with a 110. Rear gets pretty picky. A 4.25 rim will go maybe up to a 150, but is ideal for a 140.

I learned a lot doing the tires on my Zephyr 550 and in doing research for doing SM rims for the 650. By the way, the size choice I would make for the 650 would be 110/140. It is about performance, not look for me when it comes to the tires.