10 speed tranny on a cb900, how does it work?

[Truck]

I have tooled around on a 78-79( not sure of the year)  CB750, loved the look and the power.  Was looking to get one of my own but thanks to TOOLS I'm now itching to get a CB900 Custom.  I keep seeing the ads advetising a 10 speed trans.  I'm asuming this is an electronic Hi-low set up but my question is do you just switch between 5 hi and 5 low gears or do you use them like an overdrive kinda thing?  Ant info would be apreciated.

[Half-Caf]

Hey Truck, here's the dl on the 900c trans.
The engine and trans are very similar because the 900 is basically just a modified 750 engine. From the crankcase, the engine's output shaft is on the left side (just like the 750) -However, from there it enters into what they call the "sub-trans". It's here that you select from either the "High" or "Low" settings. Note that this is a manual sub-trans, too.

In theory, I guess you could use the 2 different settings for city or highway driving, but from what I've heard, most just like to throw it into "High" on the highway and use it like an overdrive setting.

Hope it helps! If you have any more questions let me know, as I've been modding a 900c

[Half-Caf]

Oh, forgot to mention something... you may already know, but the 900c's are shaft drive. One more purpose of the sub-trans is re-routing the motor's left-drive output shaft behind the engine and to the right where it runs through the swing arm. This little "detour" takes up a bit of extra space, so Honda made the frame slightly larger to accomodate. I believe the swingarm was shortened as well to offset the additional frame length.

[sgtslag]

Half-Caf, correct me if I'm wrong, but you just shift from Lo, to High, without going from 5th-Lo, to 1st-High, correct?  I asked my mechanic about it, and he told me the High range was mostly used for highway, where you just switched ranges (5th-Lo to 5th-High), once you got it up to speed, as the High range bogged in town.  Is that correct?  The High range was like Overdrive, and it reduced the RPM's, saving gas?

Saw a beautiful CB900C outside my mechanic's shop, last week, when I picked up my Voyager from him.  It was near-mint condition.  Perrrrty!  That was the first time I got a good look at the setup on its oil cooler.  I took a 900C's radiator, and mounted it on my 750, but I have it right in front of the heads -- works very well, even though its exhaust air blows over the heads.  I did not have the space to mount my radiator as high as Honda did on the 900C's, so I had to put it lower, to clear the fork and frame junction.  I have really liked the 900C's since I learned of them.  Very neat bike.  Cheers!

[Truck]

Cool, thanks for the info.  Pretty much what I expected.  Now I just need to find the right bike so I can tear it apart and make it a lil more me.

[Truck]

Oh, and post some pic's of that 900!

[shinyribs]

Do you shift hi-lo for every gear? Like a split rearend in a dump truck? Or do you shift thru 1-5 in lo,then go thru 1-5 in high? Like a road ranger tranny? Or do you shift 1-5 in lo,then just pop it in to 5 hi? Tools will know what i'm talking about on the truck trannys.. These dual range 900 trannys always confused me.

[Half-Caf]

Wow, this is stirring up quite a bit of discussion!
Truck, you wanted a pic of my 900, so here it is!


I bought it in fairly rough shape, but I basically just wanted the motor to stuff in my 750 frame.
Now I never did bother tinkering with the 900 before I took it apart, so I can make no grounded claims on riding down the road, but the mechanics I do understand..

Just remember that the 900c has the same exact gears and shifting as your 750 (internal trans)
The Sub-trans basically just bolts onto that and adds 2 more gears on top of it.
The two are not really integrated in any way other than the fact that they are bolted together.

Therefore, the 900c has the regular shift lever that controls the internal gears (comes out of the crankcase)
But, it also has a lever coming out of the sub-trans that lets you select the High-low gears as well -Make sense?

Here is how it looks on the bike:

Engine Trans -> Sub-Trans -> Shaft Drive

So, given the fact that they operate independently, I guess you could use that extra gear option a couple different ways, but once again, I hear that in the real world people use it mostly like an "overdrive" gear.

[TOOLS1]

You just use HI, or LOW. There is no split shifting.
TOOLS

[shinyribs]

Ok,thanks...sound like it would just been easier to put in a 6th gear

[Truck]

Yup, sounds like just more electronic stuff to break, Like I need something to shift into to make me go faster...

[erithanis]

shinyribs wrote

Ok,thanks...sound like it would just been easier to put in a 6th gear

My understanding is that they already needed to do some finagling to re-use the goldwing GL shaft drive on the 900 engine, re-routing the drive power from one side to the other. Somewhere along the design preocess an engineer went "hey, guess what we could ALSO do with these gears"

[shinyribs]

lol. yeah,that sounds pretty feasible.

[Thorby]

What an intriguing bike, this CB900.  I was wondering on how you would shift but I see that it's been clarified.  I see that it has about 20 HP more than the 750 but it is also heavier so I wonder now if it drag raced vs the 750 if it would be about an even match?

[Lucky 1]

Why would you want to do this???

The Cb750 frame is not as strong.