Facts about AMAL Mk1 carbs

[Little Honda]

Norvin builders know, that the smallest carb relative to bore size is the 600 or 900 series of AMAL Mk1 Concentric. Now, the best available
information, about them can be found at www.amalcarb.co.uk/TechnicalDetail.aspx?id=11

 

[Bill Thomas]

Thats strange, Does that mean, None of us should be using pilot jets ?? Cheers Bill.

 

[Howard]

Wassel are now advertising a carb that looks like Mk1 and claim all parts interchange. Also seems to be about 30 quid cheaper. Anyone tried them?

Amal now offer much improved version (finally) with better pilot jet system and hard wearing slide.

There are lots of internet sites offering mods to Mk1s - all the usual things pilot jet, float height etc - Big Sid has a few ideas too, including blending in the inlet where the square lump is at the mouth.

They're fun simple little carbs - I've spent many a happy hour tinkering with them, and when they're good, they're good .............. when they're bad .........

H

 

[Bill Thomas]

Hello Howard, But do you use pilot jets ? Cheers Bill.

 

[Howard]

Hello Howard, But do you use pilot jets ? Cheers Bill.

Yes! I haven't read the Amal site for some time, I assume from what you say, they say you shouldn't.
Their latest ad in Classic Bike Guide says they now have "a new easily removable pilot vave with precise metering of the idle circuit".

H

 

[Monkeypants]

Amal Concentrics seem to be universally despised by the mechanically inclined among our local Vincent club. I agree that the originals had a problem with slide wear, but that can be dealt with by purchasing the new anodized slide or by having the carbs sleeved.
Other than that, they are small, simple and work well. I have Mikunis on the one Rapide, Concentric mk 1s on the other. The bike with the concentrics is easier starting and generally goes better than the Bike with the Mikunis. I think the tickler on the Amals is helpful for cold starting. It seems more effective than the enrichener circuit used by Mikuni.
Over the years Ive had a few bikes with Concentrics and quite a few with Mikuni , Kiehin and one with IRZ, no big problem with any of them but I find the Amals to be about the simplest of the lot.
In the past a number of Commando owners have converted their bikes from twin Amal Concentrics to a single Mikuni. Now that trend is reversing with the realization that the bikes run great with the Amals plus make a whole lot more power on the dyno with the twin carbs vs single.
Similarly, it has been a popular mod to replace the original 40mm Bing on the 490 Maico with a Mikuni, the claim bein that starting and low speed running is improved. My Maico came with a Mikuni mounted and a Bing in the parts box. The owner of Canadian Maico Connection suggested I put the Bing back on. What a difference, all of the blood now rushes from my head during hard acceleration, whereas with the Mikuni on there a small portion remained trapped in my skull!

As far as starting ease and low speed manners, the bike has no low speed manners anyway and starting is about the same.

Glen

 

[john998]

Hello, Of my two bikes one has Mk2 concentrics, bought second hand, and the other new Mikuni's. The bike with concentrics starts better and feels crisp, the one with Mikuni's is more problematic to start, feels down on power but is better at low engine speed. Had problems with flooding on the Mikuni's also.
Perhaps I had too higher expectations of the Mikuni's
In my view the Mk 2 is a far better instrument than the Mk1. I can still hear Bill Hancock telling an enquirer about Mk1 to through them in the bin.
Regards John.

 

[vibrac]

Sometimes you have no choice our upto 73 big twin Egli had to run Mk2 Concentric
Never a problem-well one perhaps, the throttle would get stiff when she was hard at work on the track
because those big pistons were sucking the slide against the carb body.
wouldn't be a problem on the roads of the UK thats for sure....

 

[Bill Thomas]

The thing is , If you read Little Honda's post, It says the pilot jet is only for Two Strokes, Unless I have got it wrong ??, But I bet most of us have jets in !! My bike is running not too bad, And i can't face removing the jets and starting again. Funny a few years ago i loved messing about, But now i don't want trouble. I had less trouble years ago, When brother Ron and I built two 14" long Wal Philip type injectors. Cheers Bill.

 

[Monkeypants]

Hello, Of my two bikes one has Mk2 concentrics, bought second hand, and the other new Mikuni's. The bike with concentrics starts better and feels crisp, the one with Mikuni's is more problematic to start, feels down on power but is better at low engine speed. Had problems with flooding on the Mikuni's also.
Perhaps I had too higher expectations of the Mikuni's
In my view the Mk 2 is a far better instrument than the Mk1. I can still hear Bill Hancock telling an enquirer about Mk1 to through them in the bin.
Regards John.

Mikunis do seem to be subject to sticky float syndrome. I Have had that problem with mine from time to time and have noticed a couple of other Vincent owners having the same problem on the road. There is always a mechanical reason for the float problem, but it seems they are more prone to this than the concentrics, not sure why.