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Discussion Starter · #1 ·
Rec'd new pistons for my 66 and comparing them shows quite a difference in the dome on the piston. The pic on the left is the new piston and right one is the old piston. The new piston has a flatter dome. I understood that higher domes would not work in the KO model. Did the previous owner install the wrong pistons?

 

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And where did you purchase the pistons from ?
....I may need some for my Bomber.
 

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Larry.... You MAY have a 5-speed top end on 4-speed cases, or a 5-speed engine disguised as a 4-speed.....
 

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Discussion Starter · #6 ·
The serial number on the engine block matches that of the KO model. Quite possible the top end was changed but I doubt it. I found out from the son of the previous owner, that his father at one time had changed the pistons. For what reason the son doesn't know.

My problem now is I have two new pistons/rings (.75 over) with the flat dome. Will they work in this head????
 

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The inlet valves on a 5 speed head are larger with a wider bottom diameter than the KO ones.If its been messed around with previously my guess 5 speed head on 4 speed bottom end.Does it have the polished tops carbs on(5 speed) with tickover adjustment screws on outside ? This may give some indication on what the previous owner may have done.
 

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GAMD5 said:
The inlet valves on a 5 speed head are larger with a wider bottom diameter than the KO ones.If its been messed around with previously my guess 5 speed head on 4 speed bottom end.Does it have the polished tops carbs on(5 speed) with tickover adjustment screws on outside ? This may give some indication on what the previous owner may have done.
Don't the 4 speed torsion bar adjusters have + or - on the cam covers??? i seem to remember something different compared to the later five speed. :) admittedly these things can be swapped. Best off measuring the valves. Exhaust valve on the 4 speed dia 32mm, 5 speed 33mm, can anyone confirm this?

Rod from OZ :cool:
 

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Discussion Starter · #12 ·
GAMD5 said:
The inlet valves on a 5 speed head are larger with a wider bottom diameter than the KO ones.If its been messed around with previously my guess 5 speed head on 4 speed bottom end.Does it have the polished tops carbs on(5 speed) with tickover adjustment screws on outside ? This may give some indication on what the previous owner may have done.

I don't have another set of valves to compare and the carb tops are just aluminum, not polished. Don't understand the tickover screws??

 

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gaillarry said:
GAMD5 said:
The inlet valves on a 5 speed head are larger with a wider bottom diameter than the KO ones.If its been messed around with previously my guess 5 speed head on 4 speed bottom end.Does it have the polished tops carbs on(5 speed) with tickover adjustment screws on outside ? This may give some indication on what the previous owner may have done.

I don't have another set of valves to compare and the carb tops are just aluminum, not polished. Don't understand the tickover screws??


Ok that valve on the right is identical to my 4 speed ones i have. I have the answer the exhaust clamps (the ones that hold the pipe to the head) are different and there bolt spacing is also different. do you have a photo of the exhaust clamps??

Rod from OZ :cool:
 

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Hey just to throw a spanner in the works, the Honda parts book for the 4 speed lists the 5 speed head as the superseded replacement :shock: (printed 1971)

Rod from OZ :cool:
 

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gaillarry said:
What's the spacing of the bolt holes in mm :D

Rod from OZ :cool:
 

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gaillarry said:
You my friend have a 4 speed head :D as the 5 speed spacings are 69mm (ish) one last thing. Do the 4 cam caps have tiny + and - above the chrome torsion bar nut?? if they do then you should be smiling :D :D as they are 4 speed caps and hard to find.

Rod from OZ :cool:
 

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Discussion Starter · #20 ·
otr002 said:
gaillarry said:
You my friend have a 4 speed head :D as the 5 speed spacings are 69mm (ish) one last thing. Do the 4 cam caps have tiny + and - above the chrome torsion bar nut?? if they do then you should be smiling :D :D as they are 4 speed caps and hard to find.

Rod from OZ :cool:

Do you mean the cam covers?
 
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