Reason I chose mikunis was because they’re compact compared with Amal Mk2’s. Had I known the tuning nightmare, I’d have made more room and gone for Amal. I love monobloc’s – concentrics slightly less, but neither go big enough for my application. Would have had to drop to 1 ¼”.
But they’re simple. Instead of a hundred combinations of jets (which interact with each other, making for real fun) there’s very few for the Amal, so a good chance of getting the jetting at least near correct in an hour or so. A couple of pilot jets to choose from (assuming it’s not fixed) a couple of slide cutaways (usually No3) one needle and two jets (usually 105). And main jet choice. When I started on the mikunis, I found there’s several pilot jets to choose from (which affect the whole throttle range) and I calculated around 300 needle / needle jet combinations on top of the cutaway and main jet choices. The only way you’d get one of those right would be on a test bed with exhaust gas analyser and checking throttle openings in tenths. And expect to be changing jets for a whole day or longer – assuming you’ve got the whole range of jets to hand.
As Berger has found out, get it starting reliably and it won’t run. Get it running throughout the throttle range and you can’t start it. I’m in the latter category at present. And when I say ‘run’ I mean just and only that. Whether it’s rich or lean I’ve no idea. I’ve been playing with these carbs for a month or more now and my patience is running very thin. It’s holding back the whole project as I have to run on a dummy tank for access to carbs, meaning I can’t fit tank or headlamp until carbs are done. Then there’s the mechanical difficulty starting to contend with. Having watched someone on youtube trying to start a Vincent I see I’m not alone……
