Topic: 1969 Cb750 Head on 76 cb750A

[Jabez5885]

Ok so I'm trying to up the performance on my 750A and was told a K cam, K head, K carbs and a big bore piston kit would wake it up. My question is I bought a K Head for $20 in an auction and I feel like it was not necessary. Just wanna clarify that it is indeed a good upgrade. Not sure if the 750k and the 750A are much different? Thanks.

[dave the welder]

rumor has it they are the same.the automatic had lower compression pistons.the round top carbs and matching cam really wake up the motor

[jonnycakes]

use the matic head with K cams, pistons and carbs

[Jabez5885]

I'm also boring out the cylinders for the 836 pistons. 10.5 compression. If that makes any difference??

[jonnycakes]

I'm almost 100% positive the heads and valves are the same "A" & "K"

[jukku]

I have Wiseco 10,25 836 ccm pistons, F2 cam, mildly ported top, K7 carbs with 108 and 38 nozzles and Boyer Bransden ignition on my Matic-Trike and it feels like there are 30 more horses at home.

[Jabez5885]

I have Wiseco 10,25 836 ccm pistons, F2 cam, mildly ported top, K7 carbs with 108 and 38 nozzles and Boyer Bransden ignition on my Matic-Trike and it feels like there are 30 more horses at home.

Did you bore AND Sleeve it or just get it bored?

[754]

Are you sure it's a 69 head..or just 69-72..   What do you have there.

[Jabez5885]

Are you sure it's a 69 head..or just 69-72..   What do you have there.

It is off a 69 cb750K is what I mean. Also have the carbs off the same bike as well.

[754]

Do you want to trade them for newer stuff like 72-76 K head and carbs.?
Can you send a top view pic of the head from the exhaust. Side, and the carbs...m email address. Is shown on bottom of my posts.. Thanks

[POPS 911]

If the 750 A'S are all the same as the K'S then why is all my 5- 1978 CB750A have valves that are hard to find ? I can grind my own cam and polish to R65......
I have a stock 1976 CB750A w/OEM 4-1 pipe with 14,000 miles that I bought off the first owner in KY for $1,100 with 9000 miles on the speedo about 10 years ago, sound as a new bike.

[Jerry Rxman Griffin aka MuthaF'er]

The 76 750A has the -392 head on it. This is from a 75/76 F or 77/78 K. You'd be better off with this head vs the early K heads.

Pops, I didn't look up your 78 but I might venture to say that yours uses the 78 K valves also considering your valves are hard to find. As you know the 78 K uses one year only valves with the keeper grooves cut differently and the -392 head also but switched to 77/78 F stronger springs, keepers and retainers.

[TurboD]

My 76 CB750A that I just finished building did not have a casting number on the head.

I pulled the head from the auto and compared it to a 77K head on my flow bench, although visually they looked to be the same head, with both in stock form the auto head actually flow better than the 77K head. If I were looking to replace a auto head with a K head, I would want go with the later heads.

I believe the A auto head to use the same valves as the pre78K model heads, as I took valves out of 3 different heads to make up a complete set that I wanted to use in the auto head.

[Don R]

 Is it possible the keepers and grooves are the difference between the valves?

[Jerry Rxman Griffin aka MuthaF'er]

78 K is a definite YES.