Differences between PGM 3 and PGM 4 Cylinders

**Fri Apr 08, 2005 6:46 pm » Post: #1 » Download Post**

Are the cylinders for both engines the same? Can they be interchanged?

Why are the pistons the same part number between PGM III and PGM IV but the rings are different?

Thanks

rip

**Sat Apr 09, 2005 1:55 am » Post: #2 » Download Post**

At a guess, they improved the design.

Maybe Stephen knows? He's inside the engine quite a bit these days. Rolling Eyes

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**Sat Apr 09, 2005 12:08 pm » Post: #3 » Download Post**

MC21 and MC28 cylinders (barrels) can be interchanged, as can pistons and rings. I believe the MC28 has (very) slightly milder porting than the MC21, but I need to get my hands on a barrel to make a port-map to confirm this for sure.

Looking at the power delivery graph of a stock MC28 would certainly lead one to assume the ports were just a little more conservative.

Differences between part numbers on the MC21/28 pistons and/or rings is often just Honda updating (superseding) the older part numbers. Simply order MC28 pistons/rings for the MC21.
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Andy.
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**Sun Apr 10, 2005 3:35 pm » Post: #4 » Download Post**

Andy wrote: (superseding)

Big seeds !

Laughing

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**Sun Apr 10, 2005 5:35 pm » Post: #5 » Download Post**

Thanks Dave, as Andy says im now catching Luke F's all time record.
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If I have to take the carbs off once more...

**Sun Apr 10, 2005 5:41 pm » Post: #6 » Download Post**

StephenRC45, soon become Stephen "The Destroyer" RC45! Laughing

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**Sun Apr 10, 2005 6:59 pm » Post: #7 » Download Post**

Or maybe just 'The barrel' Laughing

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**Sun Apr 10, 2005 7:03 pm » Post: #8 » Download Post**

What, like Jimmy "The Hood" or Stephen "The Barrel"?! Laughing

I like it!

Anyone suggesting Andy "The Tool" gets banned, OK?! Evil or Very Mad

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Andy.
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**Sun Apr 10, 2005 7:06 pm » Post: #9 » Download Post**

lol I can think of worse than Andy "the tool" for you Andy, Oh where are the pictures when I need them.
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If I have to take the carbs off once more...

**Mon Apr 11, 2005 8:01 pm » Post: #10 » Download Post**

The barrels are interchangeable, but you shouldn't mix 21 and 28 barrels. The port heights are different, but can't remember which is which.....there you go, a quality vague answer.

**Mon Apr 11, 2005 9:03 pm » Post: #11 » Download Post**

I'd put the MC28 ports lower than the MC21, judging by the power delivery.
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**Mon Apr 11, 2005 9:32 pm » Post: #12 » Download Post**

and the mc18 ports higher than the mc21,judging by the power delivery,a andy Laughing

**Mon Apr 11, 2005 10:31 pm » Post: #13 » Download Post**

Don't try that one on me Wayne... not now that you've seen the light and started trying to convert your MC18 into an MC21!! Very Happy

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Andy.
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**Tue Apr 12, 2005 9:02 am » Post: #14 » Download Post**

this is what i like to see a bit of jovial banter Laughing

just don't start on my MC16,18,21 hybrid Shocked

**Tue Apr 12, 2005 6:06 pm » Post: #15 » Download Post**

Wayne, Andys just going for ya because he knows your little stock mc18 with a set of cans would whoop his ti canned all hrc trciked up to the max 58bhp MC twentyalmostfastone NSR
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If I have to take the carbs off once more...