Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: redtractor on August 22, 2018, 08:23:15 PM

Title: cb 750 heads
Post by: redtractor on August 22, 2018, 08:23:15 PM

Have bought a spare head as my k1 is smoking and as it has been rebored suspect worn valve guides. The place I bought the head from does not know which model it came from. I suspect it may be from a k7 (Has studs on exhaust ports). So the question is - Can I put a K7 head on a K1 barrel? Any advice will be appreciated.

Title: Re: cb 750 heads
Post by: philward on August 22, 2018, 09:17:48 PM

I suspect not as I'm sure the valve/angles are different - experts will be along shortly to advise!

Title: Re: cb 750 heads
Post by: Trigger on August 22, 2018, 09:21:52 PM

Different head all together. You need a match head or why not just replace the valve guides  ;) And has it been rebored to the correct spec.

Title: Re: cb 750 heads
Post by: redtractor on August 23, 2018, 10:36:36 AM

Thanks for the replies. I was hoping to have a head refurbished so I could do a swap. The barrels have been bored out to 836 to Mark Paris spec so should be ok. When you say the heads are completely different,(I'm not being argumentative) but in what way?

Title: Re: cb 750 heads
Post by: SteveD CB500K0 on August 23, 2018, 10:54:03 AM

I'm a 500 guy...   8)

K0-K6 and F1 were the same
K7 and F2 different

Different combustion chamber shape / compression ratio
Different size valves

I will let the F2 guys chime in with any oil-way and head/barrel differences.

Steve

Title: Re: cb 750 heads
Post by: Trigger on August 23, 2018, 11:09:27 AM

Quote from: SteveD CB500K0 on August 23, 2018, 10:54:03 AM

I'm a 500 guy...   8)

K0-K6 and F1 were the same
K7 and F2 different

Different combustion chamber shape / compression ratio
Different size valves

I will let the F2 guys chime in with any oil-way and head/barrel differences.

Steve

5 different heads fitted to the K0, 2 different heads fitted to the K1, 2 different heads fitted to the K2 and then between the K3 to K6 and F1 there were basicly all the same  ;)
As Steve has said, the F2, K7 and K8 were totally different animals .   

Title: Re: cb 750 heads
Post by: redtractor on August 23, 2018, 12:07:11 PM

Is there any way I can identify this head, from markings or certain measurements so I know what I've bought?

Title: Re: cb 750 heads
Post by: Trigger on August 23, 2018, 12:30:14 PM

Quote from: redtractor on August 23, 2018, 12:07:11 PM

Is there any way I can identify this head, from markings or certain measurements so I know what I've bought?

Yep, show me a picture of the head and measure the valve head  ;)

Title: Re: cb 750 heads
Post by: Spitfire on August 23, 2018, 04:48:37 PM

Some more info on heads and barrels here.
http://forums.sohc4.net/index.php?topic=99165.msg1105716#msg1105716

Cheers

Dennis

Title: Re: cb 750 heads
Post by: redtractor on August 23, 2018, 08:00:32 PM

The head is bare so don't have valves to measure but here are some pics.

Title: Re: cb 750 heads
Post by: Trigger on August 23, 2018, 09:20:34 PM

Looks to be K7/K8 as the shape of the lower front fin and the ridges in the  inlet valve gullies. You need to the valve size.
That head is not in good shape, the valve seats are rusty and the valve guides don't look much better.

Just been through a load of heads and that head is the same as a CB750 A. Don't have a clue if the A head was shared with any other 750  ::)

Title: Re: cb 750 heads
Post by: redtractor on August 24, 2018, 08:34:24 AM

Thanks for the info, guess I'll repair the head that's on it.

Title: Re: cb 750 heads
Post by: Trigger on August 24, 2018, 08:43:49 AM

Defiantly a Hondamatic  1977 head.
Easier to repair one that you know that fits  ;)