MC 28 Rear Head on MC 21 Front Barrel

**Sat Feb 07, 2015 2:03 pm » Post: #1 » Download Post**

Hi Guys,

I have been an NSR250 owner since 2005 when I picked up an RK5 MC18 (Which is back home in Toronto). I just recently bought a 1991 MC21 SE to ride here in Dubai as well.

I was curious if there were any issues fitting and MC28 rear head to the MC21 front cylinder? I know the engine differences were minor and it has basicaly remained unchanged since the MC21 came into production , but do remember reading that there was a small compression increase over the years.

Is anything else required besides the new HRC radiator hose (from Tyga) and the shorter plug and coresdponding cap? Will I need to adjust the carb at all? I am plannign to fit Tyga pipes and end cans at the same time as well.

Thanks in advance guys!

Ryan

**Sat Feb 07, 2015 3:27 pm » Post: #2 » Download Post**

No problem fitting an MC28 SE/SP head to an MC21 SE/SP barrel, or vice versa. (Also, no problem interchanging R heads between 21R and 28R, just don't mix R and SE/SP unless you know why you are doing it!)

One of the studs in the barrel will be too short, so you will need to sort that too. Be careful extracting the stud, as it's easy to damage the barrel if it's in tight! Soaking the day before with penetrating oil may be a good idea, if it looks corroded. (Especially true when removing MC16 and MC18 studs, as the barrels are considerably weaker in that area to MC21/28.)

You will ALWAYS need to check the jetting with ANY modification. To not do so risks the possibility of detonation damage to the piston/head, at the very least, although this modification is aimed at reducing such chances in the first place. You should always be prepared to make carburetion changes.
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**Sat Feb 07, 2015 9:14 pm » Post: #3 » Download Post**

How can you tell the difference between a SE/SP cilinder(head) and an R cilinder(head)?
Is there an code or something?

**Sat Feb 07, 2015 9:17 pm » Post: #4 » Download Post**

SE/SP heads are marked KV3-L
R heads are marked KV3-H
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**Sat Feb 07, 2015 10:31 pm » Post: #5 » Download Post**

Aah good to know.
And is there also a difference between SE/SP and R barrels?
And if so what are the codes?

**Sat Feb 07, 2015 11:06 pm » Post: #6 » Download Post**

Time to do some searching, I think!

The forum's been here 15 years, and this has all been covered many times before! Wink

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Andy.
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**Sun Feb 08, 2015 10:22 am » Post: #7 » Download Post**

I did, but I think my searching skills aren't that great.
Sorry that I am wasting your time with my stupid questions Smile

I will try again. Thanks

**Sun Feb 08, 2015 3:19 pm » Post: #8 » Download Post**

http://nsr250.net/forums/viewtopic.php?t=6057
http://nsr250.net/forums/viewtopic.php?t=3077
http://nsr250.net/forums/viewtopic.php?t=9090
http://nsr250.net/forums/viewtopic.php?t=2544
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Andy.
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**Sun Feb 08, 2015 5:06 pm » Post: #9 » Download Post**

Great Andy, already found them.
Is there any difference in the front and rear cilinders?

**Sun Feb 08, 2015 5:10 pm » Post: #10 » Download Post**

Mikestrike wrote:
Is there any difference in the front and rear cilinders?

No, no difference at all.
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Andy.
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**Mon Feb 23, 2015 5:07 pm » Post: #11 » Download Post**

Thank you Kindly Andy!

Have a good one

Ryan