05-23-2017, 10:29 AM
(05-23-2017, 08:36 AM)Wolfgang_imp Wrote: The CB1100 speed limiter can not be removed without disablement of the speedometer.
However, as we have all noticed....most motorcycle speedometers read 5 to 8 mph too high. (i.e. it indicates you are traveling at 60mph when your true speed is 52-55 mph)
I saw this in both my BWW and Kawasaki speedometers.
Now....back to the speed limiter.
In my case I simply want it to allow the bike to do at least 120 mph after I have had the ECU reflashed to remove the rev limiters, and a Yosh exhaust installed. That should make the bike quick enough and fast enough to avoid being embarressed by some Harley.
Now to the theoredical fix. The CB1100 has a sensor ring on the rear wheel that is used to determine the bike's speed. You can not remove the ring, or disconnect the speed limiter wire, without loss of the speedometer readout.
The CB1100 comes with a 140-70 18 in. rear tire. If you replace that tire, when it wears out, with a 140-80 18 in. tires the "taller" replacement tire will yield an increase is speed, over the 140-80 tire...of about 8-12% (conservatively) ....at the same rpm. (depending on the tire you select). What you are doing is changing the aspect ratio of the stock tire to a tire that is taller and has an increased diameter. Kind of like the old steam locomotives. They had limited revs to work with so they used smaller diameter driving wheels on freight locomotives that did not need to go fast, but pulled heavy loads.....and larger wheels on the passenger locomotives that pulled lighter loads and needed to enjoy increased speeds.
112% of 112 mph is about 125 mph.
If you are worried about losing acceleration due to the "taller" tire....drop the front sprocket on tooth. Generally that is worth a 8 - 10% reduction in gearing that will bring back the acceleration.
If you are worried about clearance the to front of the swing arm with a taller tire the smaller sprocket will give you a bit of chain slack and allow you to pull the rear wheel backwards away from the front of the swing arm.
I am going to try this change on my CB1100 ....when the time comes for a new tire.
Wolfgang
Actually, if you do the math, the diameter with aspect ratio of 80 compared to 70 is only 4.28% larger. If you multiply the new diameter x 112 mph, your new top speed is (theoretically) about 116.8 mph.
Confusion is encountered when comparing 70% of 140 and 80% of 140. There's certainly more than a 12% increase with those numbers, but don't forget the 18" wheel between the rubber has NOT changed. And don't forget the sidewall height is measured in metric millimeters, wheel diameter is in inches...
Changing front and/or rear sprockets will have an impact, but that's a discussion for another day...