350 cylinder designs

[BS Mechanic]

Can anyone narrow down when the 350 cylinder design changed?  As you can see in the attached pictures (I've also posted in my gallery), the original cylinders on my 350 GTR have pins pressed between several fins at the outer corners, and a different design around the exaust ports.  The newer (replacement) cylinder has no pins, and is much stronger around the exhaust. 

Just curious if anyone knows when this change was made in production, or if it was just replacement parts.

[Toystoretom]

I dunno but those cylinders appear to be junk. You should send them to me and I will throw them out for you   

Seriously, I wonder if after Bridgestone ceased production and they made parts for a few years in Taiwan if that's what they came up with. The exhaust flange must have been a weak spot because I have a cylinder that had been broken and someone welded it up (a horrible welding job I might add, my cat could have done a cleaner weld).

I'm about ready to have someone make up a batch of 350 cylinders, anyone speak Chinese?

[Jeff Bar]

I agree!!

The cylinders with more metal around the exhaust seem likely to be later "improved" parts. Maybe Richard know something about them?

Jeff Bar

[reed]

Jeff
I have been a motorcycle mechanic for 35 years and my time with Kawasaki they would change parts after six months.
And a lot of parts are checked and sent back to be redone and sent out again as B part instead of a A part.
Thanks.
Reed.

[OldSwartout]

My '68 350, s/n 21v04640, has original cylinders with the exhaust port cast like the "improved" cylinder.  They also have the damper pins pressed through the fins like the older cylinder in the photo, so they are a combination.

Edit:  I checked a parts bike s/n 21s01138.  It has one of each design.  Of course, I have no idea if it has had a replacement cylinder sometime in its life.