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Amal MkII concentrics

Submitted by barry_davie1 on Fri, 13/10/2023
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Commando

Shock horror I've fitted 30mm Mk II Amals to a Commando engine, not intending to upset the purists who want to keep the world of the Commando as it was back in time. 

Ive no idea what the settings should be for this set up and talking to Andover years ago they had no idea either so Ive opted for the same cut away, jets etc as the Mk I.

As the build of my bike is a bitsa albeit bits of Norton with standard 30mm inlet head set up but with modern electronic Pazon ignition and PW3 cam, the exhaust has got reverse come megga's fitted to allow easy breathing and to alert others of my existence.

So if anyone else out there has experience of MkII's any tips or pointers will be appreciated.

Submitted by paul_griffiths on Fri, 13/10/2023

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I have had nothing but good dealings with Amal over the years and only recently about my Commando so I would recommend that you e-mail them with your requirements, and wait in anticipation for the answers.

Submitted by stan_thomas on Fri, 13/10/2023

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34mm Mk2 concentrics on an 850 race bike with 4S cam, 10.25:1 compression and inlet ports shaped according to tuning sheet. Ran much better using 2C3 needles (T140E I think). Other than that, pretty much as Mk1s. Standard spray tube, .106 needle jets, 3 1/2 slides., 320 main jets, bellmouths,no filter.

Submitted by martyn_dykes on Thu, 19/10/2023

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I have just finalised the jetting of a pair of 30mm MK2s on my 750 Atlas. The engine has a Maney crank & stage 1 head with port reducing sleeves, JS rods & pistons, & a PW3 cam. The CR is a measured 9.4:1 & a free flowing exhaust fitted. The jetting is:

230 mains, 106 needle jets, 2a1 needles 2nd groove from top,3 1/2 slides, 25 pilot jets, 30 starter jets screwed into the main carb body, & 3.5 air jets. No air filter fitted.

With this set up it runs well, & since moving the pilots from the float chamber to the carb body, idles well.

Submitted by martin_seymour on Fri, 20/10/2023

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So what are the pro's and cons of fitting 30mm MK2's - weren't all Commando's 32mm Mk1's?

Would be handy to know as I have some 30mm Mk2's left over from my T140 - thought I was going to have to bore them out!

I opted for the 30mm Mk II's for the following reasons, 1/ I came across a new unused pair at a bargain price, 2/ the 850 engine had 30mm ports and 3/ how often do you have a 32mm carb wide open on the road, fingers crossed that it works out ok. Martin I would stick to 30mm instead of opening them up to 32mm I guess it depends on the port size of the head really but as I see it the only time you would use a 32mm carb is when the slide is wide open and as I recall when you've got a Commando running with wide open carbs the scenery is coming at you pretty quickly.

Submitted by paul_griffiths on Sat, 21/10/2023

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I am looking forwards to putting my 32mm carbed Combat on the road to experience that GRIN factor that only something I have put together can give me, sometime in the early spring unless I find something else to make for it!!!!

Submitted by michael_coare on Sat, 21/10/2023

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Way back in the mists of time when I actually had my 850 Commando-engined Dommie on the road (as opposed to in multiple boxes in my garage as now), I fiited a pair of those Eccentric carbs. No matter how much I fiddled about with them, it never ran smoothly...

 

I'll get me coat.

 


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