Forum

[Colin F]

Flat spot,yes my Bullet had that one after fitting a mk1.It took me +6 months
to figure that one out,very frustrating in the end what with cutouts at traffic lights.
I eventually solved the problem by holding down the tickler at lights for say 10 seconds,
everything was ok after that.Turns out the fuel level setting was too low from new.
And on this particular carb the adjustment is a bit hit and miss,you use a drift on the
fuel valve seat,anyway after a few goes i got that setting right and no more cutouts from idle.
I was silly enough to buy another one for another bike,exactly the same problem,it shows
itself if you have a particularly long time of tickling before fuel comes through.
Anyway with the Bullet i went back to the Micarb,it definitely starts easier with that on.
regards
colin

[Thack]

Yes, raising the float height is one way to mitigate the flat spot somewhat. Other things you can do is richen the idle mixture, so it's a bit richer than ideal, and/or fitting a richer slide than it "should" have.



They are all bodges because really they hide the symptoms, rather than cure the actual design fault, and they all affect the mixture elsewhere.



Having said that, I must emphasise that many people find the Mk1 Concentric perfectly acceptable. The right combination of float height, idle mixture and throttle slide can render the flat spot unnoticeable (and some people don't notice it anyway, or don't care about it). The mixture will usually be a bit too rich at idle and small throttle openings, but most engines tolerate that far better than running too weak. Lab tests back in the '70s which measured the behaviour of several different makes of carburettor (published in one of the biking magazines) showed the Amal to have the worst mixture control of them all under the full range of operating conditions.



But I must repeat: many people find the Mk1 Concentric to be perfectly acceptable on the Bullet. And as I say, it's very cheap and you can get all the different bits you need to tune it with no problem at all.

[mauri]

you can order a mk1 premier from our host, just specify in the notes when you order.



i have one mounted on a 535 conversion.



its only recently been done, so can not comment to much on the longevity of it.

what i can say is



pro

the material of the carb body is harder, and better finished than the older ones

slide is hard anodized.

stayup float in the bowl.(weird way of solving a manufacturing problem!)

viton tip on aluminum needle valve.

easy accessible pilot jet.



cons

still have to handle an air slide on warm up, no true cold start.

non adjustable air jet.

still lacking in top performance.

remains a archaic set up.

only slightly cheaper than a mikuni.

its an amal.



on overal finish and value for your money your better of with a mikuni.

[Pathfinder856]

Thanks for your replies.
I am not sure now, I do like the look of the Amal, but it sounds like I may be better off with a Mikuni !
I take my biles to a local bike shop, he has a varied racing career and owns everything from Flat tankers to a Yamaha R 1
He has his own bullet and he rated the Mikcarb and says he likes them better than the Amal.

Maybe a Mikuni is the way to go ?

[Norm]

Change a Micarb for a Mukini.....why?

[Pathfinder856]

Well I was hoping to change to the Amal
Because I wanted slightly better performance, but mainly because it looks right for the bike, but because of what I have read, I am having second thoughts.
I know that the Mikuni will probably be a lot better, than either theAmal or theMikcarb, which I believe USA Mikuni built under license.
I know the standard carb is set up to pass stringent emissions regs , so was Hopi g for something that was slightly freer breathing .

[Adrian]

The Mikarb (Indian rather than USA made) can be tuned, our hosts sell the bits, though be careful. A friend went down the tuned Mikarb route along with other tuning mods and seized several pistons before working out the needle jet selection (i.e. the richest available) was critical!



All sorts of non-Amal carbs have found their way onto classic-engined Bullets, including Dell'Ortos, Mikunis and even Keihins on some of Fritz Egli's specials. The US importer also sells a flat-slide Keihin clone that is supposed to work well.



A.

[Pathfinder856]

Sorry predictive text that should have been is a, not USA !

Thanks again

Rich

[Thack]

Adrian writes: "A friend went down the tuned Mikarb route along with other tuning mods and seized several pistons before working out the needle jet selection (i.e. the richest available) was critical! "



To be fair, you run just the same risk with any other carburettor - if you get the mixture wrong enough you can cause engine damage. So, especially if you've modified the engine in other ways, you need to be just as careful when setting up an Amal as a Micarb.

[Pathfinder856]

Well, I have made a decision, I have just ordered an Amal concentric Kit from our Hosts, but substituted the Mk 1 Concentric for an Amal Premier.
Which is basically a Mk1 Concentric, made of a better Alloy, with a hard anodised slide, better pilot jet, better float and a futon tipped float needle. These are supposed to address all the issues that you can have with the standard Mk1
And it looks the same, so will give me the styling that I was looking for.
I know the mikuni may well be a better carb, but it does not look any different to the Mikcarb, the Amal looks the part on the bullet!

I am not too worried about slightly worse fuel consumption . And I'm not going to race the bike so I can live with the Amal over the Mikuni .

I will let you know how I get on with it when it's all set up and running

Thanks for your help guys.

Next improvement may be be the high capacity oil pumps !