Topic: who knows gear ratios in the transmission? 550 vs. 650

[paulages]

i've begun mocking up my 550/650 frankenstein beast, and i'm trying to decide whether to use the gearbox from the 550 or the 650. the clutch basket itself is exactly the same, however the gearing is different from the primary shaft to the clutch gear, making it hard for me to understand how the different gear ratios would work out at the rear wheel.

does anyone have the 650 gear ratios? my clymer doesn't have them. also, does anyone have both bikes and can comment on the difference in feel through the gears?

[scunny]

650 according to Haynes
Primary reduction......2.737:1
Final drive ratio..........2.500:1 (16/40 sprockets)
Gear ratios (overall)
1st gear........2.500:1
2ndgear........1.722:1
3rd gear........1.333:1
4thgear.........1.074:1
5thgear.........0.885:1

[paulages]

okay. so they're all a bit lower on the 650, until the final drive. the lower primary is supposedly the reason for the "better" clutch on the 650 (the baskets themselves are exactly the same). i'm wondering if the slightly higher final is enough to make up for the difference, or if the 650 still ends up with a slightly lower ratio profile. and i'm wondering if this would affect the torquey feel of the 550 if i used the 650 gears.

here are the specs:

                550             650
primary:      3.063                               2.737
1st             2.353                              2.5
2nd            1.636                              1.722
3rd             1.269                              1.333
4th             1.036                              1.074
5th             0.900                              0.885
final             2.176                              2.5


the differences would seem pretty clear through the gearbox (for example, 5th gear looks like you'd get a little more out of it on the 650), except that the primary and final ratios are different. anyone know some equation to run the variables through to compare? if one were to use the 650 primary gearing for example, and the 550 gearbox...the ratios would be the same in the gearbox, but would end up different at the back wheel. i guess if i really have a chance to think about it, i'll figure it out. in the meantime, if anyone has ideas...     

[paulages]

if my math is correct, a 650 primary (89% lower ratio than the 550) with a 550 gearbox, and a 16/39 sprocket combination would give a 2.44 final drive ratio (1.123 % higher than 550 stock), which would compensate for the primary reduction.

now what i'm trying to figure out is whether to mix up gears to get closer ratios...

[scunny]

I'll leave the math to you but I think to decide on gear ratios first you need to decide how the bike will be used, close ratio for drive out of corners etc or a more well spread box for general riding

[Pinhead]

I wouldn't put the gears any closer than they already are. As I drive my 650 around I wish the gears were more spread out so I could have a little taller highway gear without losing take-off in first. I'd really love to run 4500 at 70 mph instead of 5000, but if I up-sized my front sprocket any more I fear I'd lose too much in first.

[bryanj]

Careful with the mix-n-match as Honda also altered thr profile of the teeth and even a gear with the same number of teeth may not "mesh" correctly. Gets even worse in a 500 as the "end" thrusts are machined different! Took me an age to set up a 500/550/650 hybred gear set into a 500

[cb650]

Remember there was a few diff final drives of the 650.    79 was diff from rest and the custom/standard was diff in other years.  79 and standards had 17" rears and the customs had 16". I believe the 82 nitehawk had diff gears internally.





                        Terry

[paulages]

i'm currently planning to just stick with the 550 gearing, except that i'll have to correct the final drive ratio to compensate for the reduced ratio of the 650 clutch basket.