Topic: HOW to Engine CB750 '73 Upgrade for street use only

[PeWe]

Where have all old ported heads from the 70-80's gone?
It must be many collecting dust and no longer used waiting for a seat and valve job.

[Ilja]

Where have all old ported heads from the 70-80's gone?
It must be many collecting dust and no longer used waiting for a seat and valve job.

I think so... I have at least two heads for every bike I own. XD
... but I just saw this: https://www.ebay.co.uk/itm/Oversized-Intake-Valves-Honda-Four-CB-750-K-SOHC-69-77-34mm/273093318769?_trkparms=aid%3D444000%26algo%3DSOI.DEFAULT%26ao%3D1%26asc%3D20170221122447%26meid%3D013483a1238346a380b88bcdd3d85638%26pid%3D100752%26rk%3D5%26rkt%3D6%26sd%3D273093320079%26itm%3D273093318769&_trksid=p2047675.c100752.m1982

If it's possible to install 34mm valves in the K/f1 heads, then why did they go through all the trouble for the F2 head?
I'm porting my f1 head for RS34 and am installing these 34mm valves, and then I will just run my current "cheap" 836cc flattops instead of expensive pistons.

[MRieck]

Where have all old ported heads from the 70-80's gone?
It must be many collecting dust and no longer used waiting for a seat and valve job.

I think so... I have at least two heads for every bike I own. XD
... but I just saw this: https://www.ebay.co.uk/itm/Oversized-Intake-Valves-Honda-Four-CB-750-K-SOHC-69-77-34mm/273093318769?_trkparms=aid%3D444000%26algo%3DSOI.DEFAULT%26ao%3D1%26asc%3D20170221122447%26meid%3D013483a1238346a380b88bcdd3d85638%26pid%3D100752%26rk%3D5%26rkt%3D6%26sd%3D273093320079%26itm%3D273093318769&_trksid=p2047675.c100752.m1982

If it's possible to install 34mm valves in the K/f1 heads, then why did they go through all the trouble for the F2 head?
I'm porting my f1 head for RS34 and am installing these 34mm valves, and then I will just run my current "cheap" 836cc flattops instead of expensive pistons.

Those 34mm ebay valves won't work in the f2 head....they are to long and keeper groove is different.

[Ilja]

Where have all old ported heads from the 70-80's gone?
It must be many collecting dust and no longer used waiting for a seat and valve job.

I think so... I have at least two heads for every bike I own. XD
... but I just saw this: https://www.ebay.co.uk/itm/Oversized-Intake-Valves-Honda-Four-CB-750-K-SOHC-69-77-34mm/273093318769?_trkparms=aid%3D444000%26algo%3DSOI.DEFAULT%26ao%3D1%26asc%3D20170221122447%26meid%3D013483a1238346a380b88bcdd3d85638%26pid%3D100752%26rk%3D5%26rkt%3D6%26sd%3D273093320079%26itm%3D273093318769&_trksid=p2047675.c100752.m1982

If it's possible to install 34mm valves in the K/f1 heads, then why did they go through all the trouble for the F2 head?
I'm porting my f1 head for RS34 and am installing these 34mm valves, and then I will just run my current "cheap" 836cc flattops instead of expensive pistons.

Those 34mm ebay valves won't work in the f2 head....they are to long and keeper groove is different.

Yes, the F2 head also already has 34mm valves... I wanted to keep those valve sizes so was planning on buying special F2 pistons for conversion back to N/A.

But now I can just upgrade the F1 head (=K) with these valves so it's also 34mm, and install that head to get back at normal N/A compression with my current pistons instead. 

[PeWe]

My K6 head got F2 in valves as an upgrade