Need stock combustion chamber volume and stock valve size list for all models

[Aubreymason]

As the title suggests; I need a list of the combustion chamber volume and valve sizes for every SOHC model....

I restore and rebuild SOHC's and while I can obtain a head from every model to measure them - I am inquiring to see if anyone else has already done this to save time and cash...

 

[dirtdigger]

All K use the same size valves. ex 28mm intake 32 The F supersport use the larger valves. ex31mm intake 34mm Combustion chamber volumes vary greatly, even on the same head. K's seem to be in the 22 to 24cc range but shape and volume vary, early ones hand blended from the factory later ones chambers got little larger and not as refined as not as much care was taken in manufacture to meet the demand of the bikes. Have seen 1cc variation on the same head...big different on a small motor. The supersport heads are in the 28cc range.

 

[amc49]

Just sinking the valves chasing good valve seal will change the volumes on chambers that small.

 

[Aubreymason]

All K use the same size valves. ex 28mm intake 32 The F supersport use the larger valves. ex31mm intake 34mm Combustion chamber volumes vary greatly, even on the same head. K's seem to be in the 22 to 24cc range but shape and volume vary, early ones hand blended from the factory later ones chambers got little larger and not as refined as not as much care was taken in manufacture to meet the demand of the bikes. Have seen 1cc variation on the same head...big different on a small motor. The supersport heads are in the 28cc range.

Understood - and the reason why I'm asking... to see if anyone has ever done this before.
Case in point: I have a 78 F I am currently working on and the volumes of each chamber are not the same.... 2 are blended, unmasking the valves while 2 are not unmasked..

I've been doing headwork for far too long to believe this should be "normal" to find.

Has anyone ever found a line into Honda itself to ask them?

 

[dirtdigger]

What you are describing is not factory, Honda never did much work at the factory on the heads, early ones had blending in the ports but not really anything in the the chamber. Later ones basically nothing was ever touched in the head, no blending or shaping done. Maybe send a picture I can take a look at.

 

[dirtdigger]

It has been documented the the first 750s off the line definitely had hand port work done to ports. This practice did not last long as it took too much time and cost to much in labor as the demand for the 750 skyrocketed. The hand work is rare and I have never seen a factory head that WAS hand ported. If your 78 has blending done it wasnt from Honda

 

[Aubreymason]

It has been documented the the first 750s off the line definitely had hand port work done to ports. This practice did not last long as it took too much time and cost to much in labor as the demand for the 750 skyrocketed. The hand work is rare and I have never seen a factory head that WAS hand ported. If your 78 has blending done it wasnt from Honda

When I took it apart it still had factory gue holding the head and cylinder... on a bike the speedo says only has 4,500 miles....
Somebody did it.

Some of the shiny is from me cleaning the carbon out of the chambers - but you can see where someone has blended and unmasked the intakes in 2 cylinders.... the sharp edges are gone...

 

[dirtdigger]

From the factory Honda didnt use anything to hold the gaskets on, I suspect a dealer had the head off at some point if it had something on it.

 

[amc49]

Looks as well like someone used a non-stock exhaust spotface cutter in there too, the cut goes way past the casting circle on one there. Maybe some repair done on the chambers.

 

[Aubreymason]

I reiterate; the speedo says the bike only had 4,500 miles on it....
So I'm puzzled....
If a repair was done, it was done very early in the life of this engine... so why?
I've never heard of a valve problem on a brand new SOHC engine... and I was pretty up-to-speed on these when they were new.. I owned one.

 

[dirtdigger]

The 77 and 78 f engines had well known problems with valve guides and the spring retainers. The retainers have been know to fail under 10000 miles. Valve pulls through the retainer=valve and piston collision. The retainers have a steep angle plus poor metal...common issue on the f motor. The exhaust valve guides definitely did wear out under 10,000.

On top of that on this old of a bike I definitely dont trust what the odometer says....to easy to swap out or crack open and change mileage or disconnect. Unless previous owner is known I never believe the odo.

 

[amc49]

NEVER take a bike speedo at face value and even more so on collectable ones like these SOHC. You can find another one and change it out in 3 minutes. And like said way too easy to get into them to alter as well.

And with some riders 4500 miles is a lifetime, I often bought bike engines messed up before that. My own first DOHC burned several valves at 3000 miles, it had help of course.