Author Topic: CB750 K transmission vs F2 - number of teeth?  (Read 2168 times)

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Offline PeWe

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CB750 K transmission vs F2 - number of teeth?
« on: November 12, 2017, 10:12:20 PM »
The CB750 shop manual describe the transmission for K0, K1-K6 with gear ratios gear by gear.
Nothing about number of teeth
-Anyone that has a description for F2 transmission?
« Last Edit: November 13, 2017, 05:22:43 AM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline robvangulik

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Re: CB750 K transmission vs F2 - number of teeth?
« Reply #1 on: November 13, 2017, 12:40:52 PM »
I've been searching deep in my archives (it is 27 years ago i sold my last cb750) and i found these gear ratio's for theF2:
1st gear 2,500:1
2              1,708:1
3               1,333:1
4               1,133:1
5                0,969:1
I can't find the ratio's for the earlier models, but i seem to remember the 4th gear was 34:31, which should give 1,096:1, and the primary drive for the F models was shorter too, but i can't tell the numbers anymore,you could look at hondachopper.com

Offline PeWe

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Re: CB750 K transmission vs F2 - number of teeth?
« Reply #2 on: November 13, 2017, 01:53:57 PM »
Thanks,
I found that too in the shop manual.
I have added the internal gear ratio for F and F2 into the gearing excel file I have found here, hopefully correct. I have adapted it for km/h.

If need to change the kmh to miles, remove the *1,60934 factor I have added on each kmh cell. See the first tab with K where the initial mph is written.

It look like its only gear 4 and 5 that differ. F and F2 has different front vs rear sprocket.

I'm still open for gear teeth numbers if anyone knows....
« Last Edit: November 13, 2017, 01:58:32 PM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline robvangulik

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Re: CB750 K transmission vs F2 - number of teeth?
« Reply #3 on: November 13, 2017, 03:30:43 PM »
I found this at hondachopper.com for the F1 onwards:
Quote
Final drive gear ratio 43/50 i/o 48/50. 4th gear on main shaft 31 i/o 30, 5th gear on countershaft 31 i/o 32

Offline PeWe

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Re: CB750 K transmission vs F2 - number of teeth?
« Reply #4 on: November 13, 2017, 09:37:10 PM »
Final drive gear ratio 43/50 i/o 48/50. 4th gear on main shaft 31 i/o 30, 5th gear on countershaft 31 i/o 32

Thanks! That seems to be the gears teeth and match the internal gear ratio where only 4 and 5 differs.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967