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Pop quiz

  • Thread starter Thread starter wera racer
  • Start date Start date
W

wera racer

Guest
Okay, I need some help with the math on my GS1000 vintage racer. I only have a tach and would like to estimate my speed.

The manual says the "primary reduction" is 1.775 (87/49), which I presume is the crank to trans input shaft ratio, but which is which? One rev of the crank equals 1.775 trans shaft revs, or the other way around?

If I can get that answered, I can do the math from there since fifth gear is 0.9615 (25/26), I know my sprockets and can measure the tire circumference.

I suppose I could put a degree wheel on the crank and determin how far the rear wheel travels per crank rev and get close.

School is now in recess.
 
Alls I know is just about every GS ive owned, 3rd is roughly 1000RPM for 10mph. I think I said that right. 35 mph in third is just about 3500 rpm. Maybe like 3450 or something like that.
 
wera racer said:
Okay, I need some help with the math on my GS1000 vintage racer. I only have a tach and would like to estimate my speed.

The manual says the "primary reduction" is 1.775 (87/49), which I presume is the crank to trans input shaft ratio, but which is which? One rev of the crank equals 1.775 trans shaft revs, or the other way around?

If I can get that answered, I can do the math from there since fifth gear is 0.9615 (25/26), I know my sprockets and can measure the tire circumference.

I suppose I could put a degree wheel on the crank and determin how far the rear wheel travels per crank rev and get close.

School is now in recess.
Click to expand...

you need to consider:
F/R sprocket ratio
gear box ratio
R tire size

best to go use the application Katman has linked to his site.

http://www.suzuki-katana.com/sprockets_gearing.html

http://www.gearingcommander.com/
 
Last edited:
wera racer said:
The manual says the "primary reduction" is 1.775 (87/49), which I presume is the crank to trans input shaft ratio, but which is which? One rev of the crank equals 1.775 trans shaft revs, or the other way around?
Click to expand...

Other way around. The crank turns faster than main transmission shaft. Remember, it's a "reduction" gear.
 
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