Stephen's F3 is an inspiration!I notice on the motor that the front head looks like a "front" head,and not a rear head conversion.any reason why this is so?as I understood that the conversion was a HRC modification.
I'm sure Stephen will tell you more soon.
From what he told me, they're F3 heads. Different dimensions to stock/SP heads. Not sure if they're machined with a straight or more straight spark plug position.
The rear head on the front is actually an MC28 SS/SP modification... they need all the help they can get!
The MC21 never used a head conversion, and as Roy says, the F-III heads are Fr/Rr styles, just as the standard ones. _________________ Andy.
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The casting for both heads is the same as stock. The plug position is also the same as OE.
The internals are different though having a tighter squish but less compression that the standard heads. They also say RR on the casting the same as the SP heads.
As Andy says the rear head on the front was a MC28 HRC idea.
The F3 one's don't come up very much now so I machine stock ones now as and when I need more. Front heads are also cheap which is a good thing as no one wants them! _________________ If I have to take the carbs off once more...
Location: Cheshire, U.K.
Sun Apr 11, 2010 9:26 pm » Post: #23 » Download Post
"Been getting some more done to the bike over the last couple of weeks.
Fitted some straight plug MC18 F3 heads that I got " .
This is what made me wonder about the MC21F3 head.
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