Can anyone verify if I am correct here in relation to cylinders, heads and piston part numbers.
In the parts manual it lists 3 sets of cylinders A, B and C each with 2 part numbers, 06122-KV3-950 and 06122-KV3-980.
My understanding is this:

Part No 06121-KV3-950 = A size barrel, R model(short barrel)

Part No 06121-KV3-980 = A size barrel, SE/SP model(taller barrel)

Part No 06122-KV3-950 = B size barrel, R model(short barrel)

Part No 06122-KV3-980 = B size barrel, SE/SP model(taller barrel)

etc...

For the Front cylinder heads...

Part No 12210-KV3-830 = Low compression front head, R model

Part No 12210-KV3-680 = High compression front head, SE/SP model

For the Rear cylinder heads...

Part No 12220-KV3-830 = Low compression rear head, R model

Part No 12220-KV3-680 = High compression rear head, SE/SP model


Piston B works with barrel A
Piston "no mark" works with barrel B
Piston D works with barrel C

R heads + R barrels = stock compression

SE/SP heads + SE/SP barrels = stock compression

R heads + SE/SP barrels = Below stock compression

SE/SP heads + R barrels = High compression



So, if I wanted to rebuild an MC21 motor(R model) back to standard/stock tune using "no mark" pistons, I would need to order the following compatible parts

Cylinder = Part No 06122-KV3-950 = B size barrel, R model(short barrel)

Front Head = Part No 12210-KV3-830 = Low compression front head, R model

Rear Head = Part No 12220-KV3-830 = Low compression rear head, R model

Also, could you use SE/SP cylinders and heads on an R model bottom end?

Jees, did Honda have to make it so complicated.
Anyway, hope someone can clear this up for me once and for all.

Thanks