MC21 R - "B" Cylinders

**Sat Feb 03, 2007 6:24 pm » Post: #1 » Download Post**

Hello All! I am in the process of rebuilding the topend on my MC21 R for the first time and had a few questions with regards to the Cylinders. Both Fr and Rr Cylinders are stamped "B" and as well as my backup cyl's. Does this mean that they are slightly larger bore than the "A" Cylinder? And would these require the matching B pistons part # 13102-KV3-830 ?
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**Sat Feb 03, 2007 6:27 pm » Post: #2 » Download Post**

All is explained in the Online Parts Manual! Wink

Look up the cylinder for any model and click "notes".

# mean "piston with no marking".

The MC16 parts list actually has the most accurate representation of the official Honda book.
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Andy.
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**Tue Feb 06, 2007 1:38 am » Post: #3 » Download Post**

Thanks Andy, that parts manual will be saved and used alot! The question though redundant; "B" Cyl as opposed to "A" or "C", is this just the type cyl used for my frame #'d R7L MC21 ? or again is it bore size? I appreciate all the tech info as I am in my 2nd year learning everything about my nsr.

Cheers!

Randy
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**Tue Feb 06, 2007 3:12 am » Post: #4 » Download Post**

Honda do not give bore size specifications for the MC21, only bore/piston matching data.

I you have a "B" cylinder, you want a "no mark" piston.

If you are having cylinders replated, then it doesn't really matter what piston you have - just send it along to the plater with the barrel and tell them the clearance you want! Wink

It is adviseable to stick to Honda's table though, to make it easy for future reference.

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Andy.
NSR-WORLD.COM

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**Tue Feb 06, 2007 3:38 am » Post: #5 » Download Post**

For ns400r they go for A,B,C. If you have A barrell,you need A piston Smile

**Tue Feb 06, 2007 4:03 pm » Post: #6 » Download Post**

It's all making sense, Thanks again Andy and RVT!
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