11-09-2015, 12:09 AM
Thanks to all that assist others! The forum is great. This is my first post. I was going to wait until after I did this mod, but I have a few technical questions that after revisiting my original calculations that don't add up correctly from some of the 2014 data I saw on line. Originally I posted this to 19/37 thread, but I felt it should be on its own.
My desire to do this mod was initiated by the vibration at 4000 rpm when cruising at 70mph in 5th gear. The engine has way more power and needs to go into a next gear, but none is there. Plus, I am amazed at frankly the poor mpg motorcycles are now getting. My 750 nighthawk and CB450 were well above 50 into 70s. Getting upper 40s mpg during break in when I never went above 50mph and then apx 40mpg or less now that I have done first service and do 70mph on the interstate.
If you look at the following image I am providing, it is laid out with the 2013 CB1100 gear ratios on the far left in black, then the corresponding ratios for the 2014 model in Brown, then 2 options in blue and purple for modifying the front and rear sprocket on the 2013.
I read from many that their 2014 model when they are in 6th gear at 70mph they are doing 3250, 3300, ...rpm. What ever the real number is it will not differ from bike to bike, but from my calculations, I do not see how that is possible. If you look at my image data, nothing lower than apx 3729 rpm (4000 x 0.964/1.034) would be possible - and that is not even including the 40 tooth rear sprocket that would raise it to 3825 rpm (3729 x 40/39). Am I missing something or is the 2014 data I am using flawed. How is apx 3300 possible?
This brings me to deciding on the rear sprocket size I should get manufactured. Increasing the front sprocket to 19 is all that is possible. That alone will yield a drop in rpm to 3789 (4000 x 18/19) in 5th gear.
The next question is whether to also decrease the rear sprocket to 37 or 35. If 37, the purple numbers are the final net ratios and would yield an rpm of 3595 (4000 x 37/39 x .9474) - 90%. If 35, it is the blue ratios and the rpm would be 3401 (4000 x 35/39 x .9474) - 85%. A 10% drop will increase mileage to the mid 40s at a minimum
and 15% should be upper 40s to lower 50s.
A 15% or 10% drop in final net ratio in first gear should have minimal affect on getting rolling without requiring any clutch slip. I have started in 2nd occasionally by accident without problem and that is a much larger 35% drop.
Again the main reason for looking into this was to reduce the rpm in 5th. It is way too high IMHO. This is one of the only errors in design and I do not know why they released the 2013 this way. With such a major difference, switch out, cost, upgrade to the 6gear 2014 Tx is not an option.
Feedback regarding this sprocket mod and actual confirmation of rpm on a 2014 in 6th doing 70rpm
is appreciated.
FYI, I purchased a great pair of slip on grip covers $20 that have eliminated apx 75% of the vibration through the handlebars. You may purchase the grips at http://www.misano-moto-imports.com/produ...overs.html for $16.95 plus S&H.
Pictures explaining above numbers used and of Package and What it would look like when Installed
My desire to do this mod was initiated by the vibration at 4000 rpm when cruising at 70mph in 5th gear. The engine has way more power and needs to go into a next gear, but none is there. Plus, I am amazed at frankly the poor mpg motorcycles are now getting. My 750 nighthawk and CB450 were well above 50 into 70s. Getting upper 40s mpg during break in when I never went above 50mph and then apx 40mpg or less now that I have done first service and do 70mph on the interstate.
If you look at the following image I am providing, it is laid out with the 2013 CB1100 gear ratios on the far left in black, then the corresponding ratios for the 2014 model in Brown, then 2 options in blue and purple for modifying the front and rear sprocket on the 2013.
I read from many that their 2014 model when they are in 6th gear at 70mph they are doing 3250, 3300, ...rpm. What ever the real number is it will not differ from bike to bike, but from my calculations, I do not see how that is possible. If you look at my image data, nothing lower than apx 3729 rpm (4000 x 0.964/1.034) would be possible - and that is not even including the 40 tooth rear sprocket that would raise it to 3825 rpm (3729 x 40/39). Am I missing something or is the 2014 data I am using flawed. How is apx 3300 possible?
This brings me to deciding on the rear sprocket size I should get manufactured. Increasing the front sprocket to 19 is all that is possible. That alone will yield a drop in rpm to 3789 (4000 x 18/19) in 5th gear.
The next question is whether to also decrease the rear sprocket to 37 or 35. If 37, the purple numbers are the final net ratios and would yield an rpm of 3595 (4000 x 37/39 x .9474) - 90%. If 35, it is the blue ratios and the rpm would be 3401 (4000 x 35/39 x .9474) - 85%. A 10% drop will increase mileage to the mid 40s at a minimum
and 15% should be upper 40s to lower 50s.
A 15% or 10% drop in final net ratio in first gear should have minimal affect on getting rolling without requiring any clutch slip. I have started in 2nd occasionally by accident without problem and that is a much larger 35% drop.
Again the main reason for looking into this was to reduce the rpm in 5th. It is way too high IMHO. This is one of the only errors in design and I do not know why they released the 2013 this way. With such a major difference, switch out, cost, upgrade to the 6gear 2014 Tx is not an option.
Feedback regarding this sprocket mod and actual confirmation of rpm on a 2014 in 6th doing 70rpm
is appreciated.FYI, I purchased a great pair of slip on grip covers $20 that have eliminated apx 75% of the vibration through the handlebars. You may purchase the grips at http://www.misano-moto-imports.com/produ...overs.html for $16.95 plus S&H.
Pictures explaining above numbers used and of Package and What it would look like when Installed
