Topic: F2 transmission in K6 case

[EnginebyAdam]

I have been trying to find this info on the site but am coming up short. I want to use a F2 transmission in the K6 cases I have. The F2 would give me the gear ratio I am looking for and the longer output shaft will help with setting up the slick on the rear. I know that K6 and F2 had the double row bearings but as far as I can tell the F2 case is different?

Thanks in advance.

[bjbuchanan]

I have been trying to find this info on the site but am coming up short. I want to use a F2 transmission in the K6 cases I have. The F2 would give me the gear ratio I am looking for and the longer output shaft will help with setting up the slick on the rear. I know that K6 and F2 had the double row bearings but as far as I can tell the F2 case is different?

Thanks in advance.

I can't give you actual advice but if you have no answers here post in the HI-PO/racing section, bet it has been done there

[Don R]

I've come up empty asking before, my brother claims to have done it with an F0 trans. I have an F2 trans that is backcut, the next case I split will get it. I think the K6 has the correct machining for the wide bearing. Hopefully someone knows for sure.

[EnginebyAdam]

This post shows the F2 gears being swapped in with a K6 transmission, but does not mention about the output shaft.
http://forums.sohc4.net/index.php?topic=82708.0

[BPellerine]

I think that the k8 and f2/3 share the same output shaft but diff in the upper gears.there are stronger clutch springs in the f2/3.they went to the bigger 630 chain on all 77/78 750k/f

[EnginebyAdam]

I may just end up grabbing an F2 transmission and swapping in 4th and 5th like the link I posted. I can always run a offset sprocket on front, and possibly rear if need be for alignment.

[BPellerine]

just a Q but would you make it to 5th gear on the 1/4 mile with a big motor revving high Terry in Australia has done 115 in third gear with an 836.bill

[EnginebyAdam]

just a Q but would you make it to 5th gear on the 1/4 mile with a big motor revving high Terry in Australia has done 115 in third gear with an 836.bill

I asked the same question to Jon Weeks because I found with my dohc that I was shifting to fifth right on top of the 1/4 mark. He figures all five are needed, so I'll plan as if they are

[EnginebyAdam]

Just wanted to bump this up.

Now that the 180/55/17 gsxr wheel looks to be the setup I am going with, I'm really interested to see if I can swap in the longer F2 output shaft to help with alignment.

[Retro Rocket]

I would like to know this as well...?

[Don R]

I have a project to finish before splitting a case but I'll check a K2 case wen I'm able to stop grinding chrome moly in the shop.

[EnginebyAdam]

I am seeing no reason why the F2 transmission and output shaft can't go in my K6 case. I have looked at pictures of '74K,'75K and '78F cases and I see no difference in the way the cases are machined.

Here are the links where the pictures are. Good ol' ebay :

'74K cases
http://www.ebay.com/itm/1974-Honda-CB-750-K4-CB750K4-750-Four-Engine-Cases-CB750e-2346226-/301004661507?pt=Motorcycles_Parts_Accessories&fits=Year%3A1974%7CModel%3ACB750&hash=item461546a303&vxp=mtr

'75K cases
http://www.ebay.com/itm/HONDA-CB-750-FOUR-MOTORCYCLE-CRANKCASE-ENGINE-CASE-MOTOR-CASE-LOW-END-/261345576040?pt=Motorcycles_Parts_Accessories&fits=Year%3A1975%7CModel%3ACB750&hash=item3cd9690468&vxp=mtr

'78F cases
http://www.ebay.com/itm/Honda-CB750F-CB-750F-750-F-Super-Sport-1978-1977-Crankcase-Cases-Top-Bottom-2-/380798690812?pt=Motorcycles_Parts_Accessories&hash=item58a95ee5fc&vxp=mtr

[EnginebyAdam]

This was just posted on ebay. '78 cb750F case and has the double groves for the output bearing
http://www.ebay.com/itm/1978-honda-cb-750-f-honda-750-four-engine-cases-/301055133353?pt=Motorcycles_Parts_Accessories&hash=item461848c6a9&vxp=mtr

I sent both of the ebay sellers with the "F2/F3" cases a message asking for the serial numbers off the cases to see if they are indeed both F2/F3 cases. Should help clear this up a little if they get back to me.

[BPellerine]

78k cases have the double groove as well adam.bill

[EnginebyAdam]

78k cases have the double groove as well adam.bill

Good to know Bill, thanks.

The seller with the second set of '78F cases I posted gave me cb750E-3107922 which indicates an F3 engine. Which makes sense for the two grooves in the cases.