Topic: 750 SS head issue

[classic67]

Hello fellow riders

I have a 77 supersport with bad valves. I have 2 intak valves that are chipped where the tappet sits like it was adjusted improper aswell as 2 exhuast same thing. Its going to be upwards of 400 bucks to get new valves installed? I have a good k head sitting here can i use it? Ive heard the oil passages are different between k and f but no answer if it can be done. If i can could i use the stock f cam? Sorry if this sounds jumbled just in a hurry to get this done for spring. Thanks

[seanbarney41]

I cant remember the details, but there is some fiddling that needs to be done to use a k head on an F2/3.  If you do get the f2 head redone, be sure and replace valve guides too.  It will be worth it to have the power of an f2 ready to last 10's of thousands of miles. 

[BPellerine]

if your engine has the f2/f3 pistons the valves will hit the pistons using the k head,easier to fix your f head,than do the mods needed to convert.bill

[flybox1]

^ +1
A 392 head wont fit on a 410 (head) engine without serious mods.  410 domed pistons will bend those valves.
$400 is about right to rebuild it properly.
Might find a good 410 head for less in ebay, and (at least) lap the valves and replace the seals.

[classic67]

Thank you for the replys.
I spoke to cycle x today and to get it all fixed its going to be close to 700 to do the head parts and labor. For valves guides and for some brass plugs for debry. Probly worth the money but i cant swing that. I gotta try this k head idea the only difference is the k has 8 drain holes and the f had four. I also have a k cyl handy i should be able to make something work. Any imput on the swap idea?

[70CB750]

I feel your pain, got me 78SS engine cheap and spent several years investing and fixing it - guides and valves.  Done it all myself with forums help and Neway cutters.

I think you should be able to mate K head and jugs on your engine.

[CB750F2]

Classic, as well as the difference in the number drain holes the F2 head has bigger valves than the K head and also the F2 combustion chamber volume is much bigger than the combustion chamber volume of the K head - the bigger volume is needed to accomodate the bigger valves. In order to keep the compression ratio of the F2 motor around 9.0:1 dome shaped pistons are used. So if you fit a K head to a F2 motor fitted with the dome shaped pistons the valves most likely will "kiss" the pistons. Thus you will need to fit flat topped pistons. You will also need to modify the F2 cylinders to provide oil drain back paths for the four extra holes that are in the K head. My post is just reinforcing what previous posters have said. If your cylinders and pistons are fine then I think that $700.00 to refurbish the F2 head would be your cheapest option. Pat

[classic67]

Thanks guys. I have a k head and cylenders to use so no modifying is needed to the f cyls. As far as pistons i found a set of bigbore pistons at work so im just going to bigbore the k cyls that should work fine as long as the stroke is the same.

[classic67]

I'm looking at the k cam I have it looks to have some wear. Could o use my f cam? I know the loft is alot more than stock. 74 lift was .314 later f cams were .318. I know these questions are odd I'm going through a rough patch financially so I'm trying to use what I have. I'd like to have it stock but I can't sink a ton into this. I have two friends and between us all we have tons of parts but no later f2 parts so going with a k top end is my only option. Thank you for being patient 

[70CB750]

I believe people install F camshaft as slightly hotter on K engines.

[BPellerine]

f2/3 cam is a direct fit.bill

[classic67]

Awesome i should be able to use the f towerss then aswell. Geat news. I was worried it might be to big untill i started looking at performance cams qnd they were more lift and duration than the f3