Author Topic: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?  (Read 1419 times)

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Offline MattFreeman

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Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« on: September 24, 2010, 05:33:10 PM »
Does anyone know the difference between a K (lets say a K3) final drive assembly and one from a '76 F1? 

The part #'s are different but I always thought that the '70-76 K's and the '75-76F's had the same bottom end (aside from the trans)

Can I use a K in my F2 with out changing my transmission?

Offline MCRider

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #1 on: September 26, 2010, 07:35:53 PM »
well from what I'm finding, the early shafts were set up for a single row bearing and a chain oiler. Next came a double row bearing with a chain oiler. Next came a shaft for a double row bearing and NO chain oiler. This later shaft seems to be the latest Ks (7 and 8) and the first Fs (1 and 2) Need to double check the fishies. I have all three. All three will fit in my cases. I am only interested in the double row variety and now that i know there is one without an oiler I will use that.

The one I bot off eBay was identified as a K3, but the fishies show K3s had a chainoiler and the one I bot does not have a chain oiler. This means its later.

Finally I think there is a difference in the number of teeth on the drive gear at some point and you'll need to keep that the same.

Assuming the later shafts are swappable, you'd need to swap the gear possibly.

I'm still learning.
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Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline Retro Rocket

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #2 on: September 26, 2010, 08:35:33 PM »
well from what I'm finding, the early shafts were set up for a single row bearing and a chain oiler. Next came a double row bearing with a chain oiler. Next came a shaft for a double row bearing and NO chain oiler. This later shaft seems to be the latest Ks (7 and 8) and the first Fs (1 and 2) Need to double check the fishies. I have all three. All three will fit in my cases. I am only interested in the double row variety and now that i know there is one without an oiler I will use that.

The one I bot off eBay was identified as a K3, but the fishies show K3s had a chainoiler and the one I bot does not have a chain oiler. This means its later.

Finally I think there is a difference in the number of teeth on the drive gear at some point and you'll need to keep that the same.

Assuming the later shafts are swappable, you'd need to swap the gear possibly.

I'm still learning.

Keep us informed what you eventually go with MC, i would love to use the later shaft with the double bearing and no oiler...

Mick
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

Offline MattFreeman

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #3 on: September 27, 2010, 05:46:48 AM »
Great info, thanks!!

Offline MCRider

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #4 on: September 27, 2010, 06:00:22 AM »
Great info, thanks!!
here's the evidence: l to r: 2 old style shafts w/ narrow bearing and chain oiler; 1 medium style shasft machined for wide bearing and chain oiler; 1 late style shaft machined for wide bearing and no chain oiler. The shaft is solid, though there is a slight recess about 1/2 inch deep for what reason I don't know.

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Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline MattFreeman

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #5 on: September 27, 2010, 01:16:14 PM »
Interesting. Looks like they would all fit in the case.

I'm on the lookout because mine has 60/80 k miles on it. and I'm replacing almost everything else. I figured that if I could find a low mileage one I could save myself $80 in bearings.

You could always weld the oiler closed, which is what I'll do if I have to.

Anyone know a good test for wear in this type of bearing? Mine all seem tight side to side and roll smooth, but I do not want to ever pull this bottom end apart again.

It is a big bearing, maybe they are good for a million miles if cared for?

Offline MCRider

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #6 on: September 28, 2010, 08:11:57 AM »
I confirmed with a trusted Honda mechanic that these shafts are interchangeable as long as you retain the original drive gear, if needed. The solid shaft is on the later bikes with a different 5th gear ratio. If you put it on an earlier bike you'd need to swap the gear. No problem.

I counted the teeth on my solid "K3" shaft i bot from eBay. It may have come out of a K3 bike, but someone put it there as its a late model shaft with the smaller drive gear.

The hollow shafts may be stronger in that they have more surface area. However strength of these shafts has never been an issue that i know of. The messy chain oiler is an issue (to me) and I'd love to be done with it, with no makeshift plugs.

I've known that the double row bearing while stronger also robs horsepower. I was also given the tip that there is such an animal as an "extra clearance" bearing which will pass more HP thru while still being a double row. I'm looking into that.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline MCRider

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Re: Will A "K" Final Drive Shaft Assembly Work In A CB750F1?
« Reply #7 on: September 28, 2010, 08:22:31 AM »
However if your goal is to get good used bearings by buying a used shaft, you may be disppointed. The inside bearing on the shaft I bot was very crunchy. making me suspicious of the bigger bearing. The used stuff may be sitting outside of an engine for a while and get rusty.

Bearings shouldn't be that expensive, try CBRBearing.com.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."