Hitchcocks Forum

Does any body know the best jet sizes for an Amal Concentric MK 2 32 mm for a Classic Bullet engine bored out to 535 cc , sports cams , free flow exhaust , the cylinder head has been extensively ported and I cant get it to start , spark plug is allways dry no mater how hard I try to flood it . My jet sizes at the moment are 220 main with a 106 needle assy , a 45 pilot ( was 25 ) and a No:3 slide all sucking through a S&B air filter , fittings are new , total main jet distance from head is 98mm compaired with 35mm when I used the Amal MK 1 Carb for 10 odd years , the old carb rattled and was primitive but effective , I'm in the dark on how to start the bike with this MK2 carb , its cold start is utilised but no wet plug ! Any ideas from owners who have done the conversion .

Phil, I am building a Bighead 535 project with a Concentric Mk2 (which I bought from a small ad in the VMCC magazine so needed jetting info,) and Hitchcock's suggested AS A START POINT: (I stress this is just an approximation to begin with...) Slide 3, Needle jet 106, main jet 250 and pilot jet 25. Hope this helps,
REgards, Mark

Oh, just a suggestion, when I've had problems with "Dry Plug Syndrome" I've found that removing the plug, squirting a small amount of petrol in the bore, quickly replacing plug and kicking may well get the engine running which will help diagnose the problems. It sounds as if there's a blockage in your pilot circuit or the petrol pipe or tap itself isn't allowing fuel flow.
REgards, Mark

I found the manifold a tad warped and re faced my inlet flange on the head , used known type gaskets so that area is sealed , polished the manifold surface that mates with the rubber conecter pipe , all jets bar pilot are the same , I even put a 25 pilot in the 2 stroke possition replacing the blanking screw in hope of jucing it up , spark timing is bang on for a 200002 digi ignition unit , bikes been holed up for 4 years and I cant prove that the tales of it giving a bad advance curve hence the MK 4 version now recomended but still cant flood it which I have found very handy for tuned engines with big ports , the MK 1 would flood out with the tickler , I cant do this with the MK 2 , I've got something wrong , the 220 main was my MK 1 spec and with the 106 needle and tube , even with a 45 pilot , no change , I have the full Meth coversion kit ( not cheap ) with a 440 main jet , I could try a 300 but feel the float level is too low for starting , the float is Meth resistant nylon and would be hard to bend , any suggestions , could it be my slide cutaway , I need the cold start to gush it out when needed , this is in Sydney Australia so it never gets very cold , I think that the main jet is now 60mm further away from the head compaired to the MK1 , this makes it a pig to start

All now good as I used the hand over the carb intake choke method , one big intake suck with a bit of throttle and cold star lever deployed , inch over TDC switch on and kick right though like a Gold Star with a tad of throttle , now running I can fine tune but I think it needs this proceedure and that means the S&B air filter must be off for starting , this is the age old stuation of starting tuned engines , the BIG Head 612 with Fury ports and GP 1 1/2 inch carb and race crank magneto would rank as the hardest Royal Enfield engine start you can get .In such a case I would get a speedway engine starter .