Topic: CB750 K0 Gearbox - is it inter changeable

[chaintong]

Hi there,

My Cb750 will always jump out of fourth. I can live with it, but I really need to do something about it... I have been looking on ebay for a whole 750 engine but they don't come up very often in the uk.

Does anyone know if
-1- I can still get the parts from Honda?
-2- there are any other engines with the same gearbox internals? cb750 dohc? cb 900? cb 550?

thanks for any advice

chain

[Gregorymoto]

I know this, the DOHC gearbox woll not work on a SOHC.

As far a fix i would look at the M3 racing websight, they cane help you fix your gearbox giving it a vast improvment over the  stock clunky CB trans.
Good luck
http://www.m3racing.com/

[Johnie]

Swoop...what did those shocks cost you from the dealer?

[Patrick]

According to Hondaman, the gear boxes of 1969 to 1978 SOHC 750s will interchange. The only difference between the K0 gear box and the later ones was the gear bushings in the K0 were brass and didn't wear as well as the later bushings. I confirmed the brass bushings when I pulled the tranny from my K0 last year. Even though it was in great shape, I replaced it with a tranny from a later bike without brass bushings. It was a direct swap.

Patrick

[bryanj]

There are some odd changes and mods through the years but a complete set is usually OK, Where in UK are you as i have a 750 engine on the bench to rebuild as a spare!

You can call me on 07795162623 any EVENING Sunday to Thursday inclusive.

[chaintong]

hmm I guess i'm looking for a  SOHC then..

Thanks for the help as always...

bryanj  I'm not far from J19 M6, I'll ring /txt you after thursday.

cheers

[Clyde]

If you interchange the whole gear box there should be no problem.
The F (75-78) gearboxes used different 4th or 5th gear ratios from memory. No great difference but you must obviously get matching countershaft and main shaft gears.

I would have to check- but the K7 and K8 also used a lot of 76 750F/F1 parts so be careful if you start mixing and matching.of parts
Another point to watch is that the final drive shaft gears are different on the later boxes -43/50 on the F1 and 48/56 on the early K's. Roughly the same ratio but not capable of being mixed and matched.
Regds
Clyde

[bryanj]

DONT RING AFTER THURSDAY only between Sunday-Thursday!!!
Dearly beloved gets anti if i start talking bikes on our time off

[ken736cc]

There are many differences in early gear boxes. Most gears for early models are no longer available. If you are using new gears or good used parts from another bike, count the number of teeth. Lots of gears have been changed by 1 tooth.

[Raul CB750K1]

DONT RING AFTER THURSDAY only between Sunday-Thursday!!!
Dearly beloved gets anti if i start talking bikes on our time off

Mine gets mad anytime of the week!   

[Patrick]

I agree, Raul. I think Bryan is pretty lucky if he gets a pass Thursday through Saturday, as long as people don't call about bikes....

I wish I could get a consistent pass between, say, noon and 12:05 p.m. on Thursday alone.....

[cafe750]

DONT RING AFTER THURSDAY only between Sunday-Thursday!!!
Dearly beloved gets anti if i start talking bikes on our time off

 Mine enjoys going on parts runs with me, and digging through boxes o' parts for that one piece of unobtainium that may be lurking in there...It may also help that she enjoys riding too...

[bryanj]

Well I cant really complain---She did pay for No36 for my 50th birthday, which is why the insurance were told to go away (but not in those words) when they wanted to crush it after it was torched

[754]

Remember sprocket shaft is longer in 77/78...

[chaintong]

bryan....

sorry I completely mis read you post, I ring tomorrow.

cheers

[chaintong]

and again...i only got in  at 23:15.... a bit too late to ring i think..... next week then

[bryanj]

It would have been OK mate---I work permanent nights!!!! try Monday as i am supposed to be siting in our security hut instead of driving, something about foxes and hen houses comes to mind!