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Jets and carbs for Hawkstone

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  • #16
    Ray, what type of exhaust do you have and any mods on exhaust port or others? A modern suck thorugh exhaust tends to require richer jetting than straight pipe . 106 needle jet is standard - 107 is next size up is richer. If you have needle clip on the bottom of the 3 grooves then needle is highest and you have it on the richest setting. Try it middle and then top to see if it leans it off.

    If you want to do job properly - you should start by tuning the main jet . I would go with Needle on top groove. Put in a 300 main and see if it revs out . If it does do a plug chop . If it doesn't rev out then u are overly rich - go down until you can rev out and do plug chops. Once you are happy with main then tune the mod range with the needle positions . Same procedure start rich and lean off if it doesn't rev through mi range. When you are happy with main and needle jet/needle position - then tune the pilot jet. (fast idle adjust airscrew for fastest running) If that happens to be when airscrew is fully in then you need a bigger pilot. If it is the opposite ie you need to fully turn it out then you need a smaller (unlikely) 30 is standard but most need a 35 .


    Note my 250 MDS runs a 45 pilot 107 needle and a 300 main...BUT it has a big suck through exhaust and a bog opened up exhaust port . Before the mods it ran on 270 to 290 main, 106 needle and 35 pilot.

    Hope this helps PM me is any questions. Cheers Kim

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    • #17
      Hi Kim
      Thanks for the reply, I have a Mayfield exhaust fitted already when I bought it.
      Cheers
      R

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      • #18
        All good fun

        I run my hawkstone on a 930 mk1 Amal concentric.

        My bike has a upton crank, needle roller little end, a bit of port work, an expansion chamber exhaust, motoplat ignition. It goes really well.. BUT! I think as Adrian says they can be tricky to start... ( was referring to me )

        It can be a right sod... Always goes in the end...

        My carb settings are 107 needle jet, 270 main, No 3 slide, can't remember the pilot.. I think mine is bushed, which I think is why it's a sod to start.. I've just purchased another carb to try which is unbushed.. ( fingers crossed )

        My Dads bike has all the above but with crankcase stuffers and much bigger ports and a 932 carb. He has a 260 main and a 107 needle jet aswell. My Dads bike starts first or second kick... And is really really potent but peaky...and eats piston rings

        Regards

        Scott151

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