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Old 11-10-2011, 05:37 AM   #38
DoktorT's Avatar
Joined: Apr 2009
Location: Chewelah, WA
Oddometer: 1,144
Originally Posted by bmwrench View Post
You might also consider a shorter rear drive ratio. The stock R100RT ratio is 2.91:1. A 3.20 will really make it scoot. This is probably the biggest bang for the buck.
I put the 3.2 in my 79 RS and just love it. Much better in low gears around town and can still do the ton all day long. Just much more usable for real use in all gears. With the 2.91, 5th gear is useless at less than 75mph or so. I did this so I could pull a trailer and it works super for that, but love it solo much better than the tall gears.

As to fuel mileage, no change at all with the lower gears. The engine may be turning faster, but the better torque makes up for it. I get 48 to 49.5 mpg long range on the road typically at speed limit plus 5. That drops about 3 to 4 mpg when towing the Bushtec with some 300lbs gross load. I run it 300rpm higher than solo. The only time I got just over 50 is when I maintained 3rd anfd 4th gears at 50 to 65mph for a full tank or more. Less wind resistance at lower speeds is just lots more efficient.

I had a new 76 R90/6/S years ago. Just right at 50 was typical. Recorded 53 once on a group ride all day in 2nd and 3rd on mountain twisties.

Both machines are maintained stock and precisely tuned and balanced. The S fairing is worth a mile or two per gallon. The RS is better still. 45mpg rule of thumb is good for a bare 100/7.

Like so many things Supershaft says, it's just his customers get poor efficientcy due to his by guess and by golly seat of the pants ideas. If he knew how to tune them properly, they would get the same results. Maybe as well that his clients tend to be heavy on the throttle in high gear. Cafe types trying to keep up with the riceburners. That would explain the 10mpg waste of fuel and danger to the public general and falling off the bike for a few weeks of physicians interests. How many times has he screwed the pooch? At least 5 times before this recent shunt. Are you going to take the advice of someone who thinks broked bones are required from time to time if you know how to ride or wrench Airheads?? I would want anyone who demonstrably cannot ride in a safe manner to keep his hands and tools off my Airhead, thank you. Stupid procedures yield stupid results.

DoktorT screwed with this post 11-10-2011 at 06:21 AM
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