At Mid-Ohio I was in an interesting discussion about some of the differences in the 175 line. I had noted that my bike (ser. no. 16L21087) and my brothers bike (16M22934), had a more rounded front fender than the others that were present at Mid-Ohio. So it lead me to reach for my research material when I got home. I did find some interesting documentation based on the parts book. According to the parts book for 175 DT, 175 HS, M11 RS and M11 SS, many changes seemed to have take place around the 16K, ser. no area. Front fender and front fender stays changed as the machines before 16K had different front fenders and stays, then bikes after 16K. The same thing happened to the oil tanks. Before 16K the oil tank was under the fuel tank which also had the fuel tank that was different at the front of the fuel tank to accommodate the filler for the oil tank. After 16K what is listed is the oil tank at the side. No mention is made as to whether it is only DT's or HS's that had the change to the oil tanks. I do know if one is to look at the brochures and road tests of the time, such as Cycle Worlds Jan. 1967 road test of the 175 HS and the brochure "Bridgestone--the Lion Hearted are Here", you will see both models of 175's with the oil tank clearly under the fuel tank and not on the side. I am though always cautious to use brochures and road tests as "fact" as many times they are preproduction models and they may have minor differences than actual delivered bikes. But the parts books, reflect the changes. Even though the parts books uses the changes of some items as bikes before 16K and after 16K, there is probably some minor over lap, as inventory of parts are used up. Other cosmetic changes took place after 16K. Rear fender, tool box, left cover (battery cover) and air cleaner. I have noticed where my rear wheel sprocket is a 4 bolt sprocket as my bike is 16L and my brothers 16M bike has a 6 bolt sprocket and the that the parts book reveals that a change took place at that time starting with 16M getting a different rear hub.
We all know that in production of any product, that to make a profit, the product must reach the consumer. So some items can't be as absolutes, to get the product to the showroom for sale.
I hope I didn't boar anyone with this long post.
