Sprocket change on 79 SR650

Greetings everyone,
Just thought I would post this note for anyone asking about sprocket changes as it pertains to engine RPM:
I changed the stock 16-41 sprocket combo on my 1979 650 SR to 16-40. (I was going to attempt going to a 17 tooth front sprocket but there does not appear to be enough clearence room in the forward sprocket enclosure...or whatever its' called...for a larger sprocket).
My previous RPM at 70MPH was ~5500.
My new RPM after sprocket change at 70MPH is ~5300 RPM.
Not a large difference but I am hoping a couple hundred RPM will increase my fuel economy and cruising range slightly. It does not appear to affect my performance in any noticable way.
It is only a 1 tooth difference (I figure about ~2% difference) but it may get me a couple extra miles on a tank.
I may try a 39 or 38 tooth sprocket next year. For now...IT'S TIME TO RIDE!

Interesting info for those looking to keep the revs down.

My 650 came with a 16/42. I changed to a 14/42 for some added punch and now I am going to put a 13/42 combo on. With the 810's bottom grunt and the gearing change it should be pretty quick outta the hole. Since my bike is just for playing in town, I am more concerned with straight arm pull than fuel economy.

If I am going to head out on the highway I can simply swap the front sprocket which is a lot quicker and easier than having to pull the rear wheel.

Cheers - Colin Firth-Ontario Canada

rule of thumb! changeing 1 [one] tooth on the front sprocket is like changeing 3 on the rear. 13/42 from 16/42 is going to give you more grunt, but is also more than likely going to slow you down. you may find out that in high gear your going to run out of RPM's at [lets say] 60MPH. BUT the ride to 60 is going to be fun!
I may be wrong? BUT! Regaurdless if you increase or decrease the amount of teeth on the front sprocket I thought the outside diameter would be the same, or VERY close to it. Not enough difference that you should have to worry about cover clearance. IF in doubt call any of the manufacters and they are VERY helpfull!
GOOD LUCK!