Honda305.com Forum

Hi all,

I happen to have a Honda CB77 cylinder head. The head has 10 mm spark plug holes, and at least the inlet valve is bigger, does anyone knows the part number of it ?

any help would be appreciated,

Jensen

Don't know part number but was EARLY issue and changed as the plug at times would get stuck and
break off in the head. ..........lm

jensen wrote:Hi all,

I happen to have a Honda CB77 cylinder head. The head has 10 mm spark plug holes, and at least the inlet valve is bigger, does anyone knows the part number of it ?

any help would be appreciated,

Jensen

Thanks LM, and I have a few more questions,

Did Honda change the diameter (smaller) of the inlet valve to get room for the 12 mm plug, or is there another reason for changing the valve diameter ?

Are these early heads made of another type of alloy ?

Does this head deliver more power ? Anyone did a dynoyet run with this type of head ?

Are there more differences when compared with later models ?

Is the combustion chamber the same as later heads ?

If the valve diameter is bigger, and it has the early pistons, isn't there a chance that these heads are prone to valve -piston issue's ?

If the valve diameter is bigger, the weight is higher, but these early CB's where revving higher than the later ones, what is the reason for this ?

When the valve diameter is bigger, the valve is heavier, did it have different valve springs ?

jensen

Ya have asked a lot of questions as to size/weight/design.
I'm not aware of the answers to most of them however ya can compare/measure things and get the answers and inform the list. ...........lm

jensen wrote:Thanks LM, and I have a few more questions,

Did Honda change the diameter (smaller) of the inlet valve to get room for the 12 mm plug, or is there another reason for changing the valve diameter ?

Are these early heads made of another type of alloy ?

Does this head deliver more power ? Anyone did a dynoyet run with this type of head ?

Are there more differences when compared with later models ?

Is the combustion chamber the same as later heads ?

If the valve diameter is bigger, and it has the early pistons, isn't there a chance that these heads are prone to valve -piston issue's ?

If the valve diameter is bigger, the weight is higher, but these early CB's where revving higher than the later ones, what is the reason for this ?

When the valve diameter is bigger, the valve is heavier, did it have different valve springs ?

jensen

Hi All,

This is a close up picture of the CB77 head with a 10 mm plug, look carefully at the area spark plug hole and valve seat.

Jensen