Help starting a diabolical bike!

Hi All: Firstly, thanks for your support with getting my '74 Commando roadworthy. I must begin to say that I'm new to all this..... I've finally got the bike licensed and insured, and have now taken it on the road. Once up to temperature, it runs very well indeed. I stalled it once, and one kick and it fired right up. BUT..... Starting it cold is horrible. I have a single Amal concentric Mark II with an 'enricher' rather than tickler. When I kick it over, it fires for perhaps half a second, and it doesn't seem to make any difference whether I have the enricher on or not. It will not catch. Over and over, either nothing, or it catches for a half second or so..... Could this be too lean? Any advice will be gratefully accepted!

are you depressing the "tickler" fully so to ensure that some gas seeps out between the carb bodies

and then with the enricher on, kick it over with the throttle cracked open, so that gas gets sucked in?

sounds like it is just starved for fuel when starting

No tickler on this Amal carb, just the enricher. I'm cracking the throttle open just a small amount. how 'open' do you recommend?

my 850 doesn't like any throttle at all until it fires up. I have twin carbs though and 2 ticklers. Maybe its time you investigated returning the bike back to original or having a tickler fitted. You could say mine is lean, as it needs to be revved a little after starting to warm it up. I don't have chokes on mine. No need in the warmish climate HERE. All the best though.

With this type of carb you should keeep the throttle closed until it fires.

Nielsen said:

No tickler on this Amal carb, just the enricher. I'm cracking the throttle open just a small amount.

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If it's a MkII Concentric, it won't have an "Enricher" like a Mikuni, only a proper choke and tickler. When you say enricher, is that the flat blade that rides inside of the slide proper, or is it off to the side of the slide?
Assuming it does have a proper enricher, it requires full manifold vacuum which can only be obtained with the throttle fully closed. Once you crack the throttle, the enricher quits.
If it's a "regular" Concentric with a choke, fully close the choke (choke cable slack), open the throttle approximately 1/4, then kick. However, I've never seen a MkI/II Concentric without a tickler. How about a left and right side picture?

NO Tickler . Cold - Choke Mandatory .

Maybe just to push through twice to bring the fuel up , then four times to enrichen cylinders . :lol:

One Thing , if theres a chill in the air , they dont start without that prime - Cold . :x

http://www.jerrydoe.com/norton_pdf/carb ... k_comp.pdf ready ready . Now we know why racers use bathplugs in the intake mouths . They can suck the fuel up to prime them . :lol:

Being Unhurried and putting both taps on then swaying M'Cyle between Knees to disturb floats can enhance float level . If we're lucky .
A bit like a magneto to start , with just 2MC capacitor , bare crack of throttle to let intke flow pull mixture . to much & No Suction .
As theyre not mega rich , like a flooded carb ( ticklers ) theyre a bear if the motors not warm / hot .
So you need CHOKE , at least to prime cylinders BEFORE you start . Not neccesarilly WHEN you start .

Ign. off while you pull Cyls through . though on , if you get a ' Bump ' at the kickstart , there IS fuel in there . Idea of OFF is to NOT prematurely fire it . So on , pulling it through ( foot ! ) till it bumps , will tell you how much till primed .
that plus a few will do in future . Some people can start a Sopwith Camel first swing. after pulling it through ten cylinders . :lol: . You Useually cout Cyls. FOUR once fuel up , if its cold outside , or more if its BrrrFrezzing .

Id have a cross bar bolting the two carbs as one unit , if you had two .

Nielsen said:

Hi All: Firstly, thanks for your support with getting my '74 Commando roadworthy. I must begin to say that I'm new to all this..... I've finally got the bike licensed and insured, and have now taken it on the road. Once up to temperature, it runs very well indeed. I stalled it once, and one kick and it fired right up. BUT..... Starting it cold is horrible. I have a single Amal concentric Mark II with an 'enricher' rather than tickler. When I kick it over, it fires for perhaps half a second, and it doesn't seem to make any difference whether I have the enricher on or not. It will not catch. Over and over, either nothing, or it catches for a half second or so..... Could this be too lean? Any advice will be gratefully accepted!

Click to expand...

What ignition do you have. ?

Thanks for your help, All. Much appreciated. I feel like such a Noob! Here are a couple of photos of the carb, left and right side, plus a photo of the Lucas electronic ignition system the bike came with. I must admit not checking/setting the float level when I rebuilt the carb. Having said that, the bike runs really well once it has started. It's getting it to catch when cold (yesterday was 18 degrees Celsius here in Vancouver. That's 64 degrees Fahrenheit.
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I see its SPANISH . Probly made for the Hot weather . :twisted:

Dreaded Float levels , like everything , are a recomendation . Lower stuffs it up , higher washes the oil of the rings , but 1 mm Ea way mightnt be fatal , but I wouldnt try lower . Up a Notch mightnt be a bad idea .
See you have the unavailable in the 70s Cable Choke . The lever ones were On or off .

Id Try FULL Choke for priming , 1/2 or 1/3 for starting . My lean 750 you trew the chokes of in 5 or ten seconds , as they were mega rich . Without them fitted though , bathplugs wouldve been a essential requirement .
Likely NO Throttle , pulling it through to prime . as in ZERO .

My recollection of MkIIs on a T140E was either full-choke (and no throttle) cold or no choke. i.e. Binary On/Off
I actually preferred them to MK 1s as they'd happily sit at a fast tick-over when cold, and I'd just flick the chokes off when I got going.

Have you confirmed that the choke is
1. opening properly when operating the lever - I assume it's a standard air lever?
2. closing fully (witness mark on rubber pad) otherwise.
Your brass knurled choke retainer certainly looks 'experienced'

It may be worth trying it with the cable removed from the choke lever to see if it's causing it to 'hang'.
You *should* hear the choke slide bottom out when it closes if you release the cable quickly

If it starts OK hot and runs OK, I'd be limiting the investigation to the choke circuit - blocked passages etc.

Until the recent advent of 'stay-up' floats, there was no ready means to adjust float height, and I don't recall ever 'setting' them, or needing to.
But I may have been lucky...

I like the Tee-handles, BTW

@Matt, My 'British and made in Salisbury, Wilts' MkIIs have Made in Spain on them. Burlen assure us that that's just where the casting was done.
No issues whatsoever with the quality.

That RITA won't last forever. How were they for starting?

sorry..... what's a RITA?

So I checked the choke cable and all seems to be in order. I pulled the plugs, thinking that maybe my mixture was too lean, but if anything, they were sooty--though not at all wet.

Meanwhile, I gave it a couple of cranks with full choke and ignition off. Then crank with part throttle and ignition on. It fired for about 1.5 seconds, which is progress. Then nothing. So I repeated the operation. Same result. On the third repeat of the off-ignition-two-cranks-on-ignition-throttle-part-open it caught and ran well. Still seems to me too difficult to start, but better than yesterday.

It is, too hard to start. Are you confident the carb and all it's circuits are clean and it is jetted properly.If you are maybe for shits and giggles you should try full choke on ignition off and kick full through half a dozen or so times and then try with ignition on.It would be interesting for you to look at plugs after kicking a few times with ignition off too , to see if gas is getting to them.Keep us posted
Craig

check your battery charge - the rita needs a good battery to fire properly

Battery is brand new.

yeah but is it charged up / showing 12.4 + V or so when key is turned on?

Nielsen said:

Battery is brand new.

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Your pictures tell a world. To reiterate my earlier comment, the enricher circuit relies on manifold vacuum to operate, meaning the throttles must be completely closed (idle position) for the enricher to work. This not only richens the mixture, but adds some extra air. It's a kind of built-in fast-idle.
Just as soon as you open the throttle any amount, they fall out of the circuit. That's one of their advantages in that they won't cause you to go slatheringly rich when trying to "clear its throat". I love 'em!

When working properly, they allow the engine to start cold and up the idle speed to 1500-2000 rpm. You should be able to open the enricher, no throttle, kick it over once or twice, and it should start easily and go on high idle once it catches. If it doesn't, there's a good chance the enricher jets are plugged, very much like what happens to the idle jets from lack of use. Take a look at http://www.who-sells-it.com/cy/brit...tish-motorcycles-20367/page-125-fullsize.html and scroll to the bottom of the page for a look at item #40. Make sure they're clear.

Nathan

Nater Potater: Thanks for your reply. Much appreciated. By 'item # 40' I assume you mean the very bottom of the choke cable assembly in the diagram you linked: that brass rod-like piece. I did notice when I unsrewed the choke assembly from the carb body that the very bottom of the choke assembly (#40) has a somewhat deformed rubber gasken on its bottom--which would presuumably contact the bottom of the carb. I didn't touch that bottom piece, only making sure that the whole slides in its cylinder--which it does. I'd better take a look at it again. I cetainly didn't notice anything looking like jets on it because, as I say, the bottom of #40 is mostly covered by that rubber gasket. Not going to get to it for a couple of days, but will report back.