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Posted: **Thu Mar 16, 2006 11:59 am**

Hi
I am putting my old racing 250 mach1 back together after many years for road riding . The head has been ported out to 34mm it has a forged Borgo piston and factory red/white cam . I have a new Amal MKll smoothbore carb which i intend to fit but have no idea where to begin with jet sizes ! anyone got any suggestions for a starting point ?
Thanks
Mike

Posted: **Sat Mar 18, 2006 7:38 pm**

I have a 34mm smoothbore on a racing 250 Mk3.

Slide: 3

Needle: 2A1, set on middle notch.

Needle Jet: 106

Pilot Jet: 25

Main Jet: 210 (using either 50/50 Avgas 100LL/Premium or 110 Octane Leaded racing fuel)

Air Screw: Turned out 1 3/4 turns.

Try those.

Posted: **Sun Mar 19, 2006 1:22 am**

Thankyou that sounds like an excellent starting point
Mike

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Amal MKll carb on 250 engine jetting ?

Amal MKll carb on 250 engine jetting ?