Choke issue amal MK1 1969 commando

Migsan

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Dec 9, 2020
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88
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Hi everyone
I am having an issue with the choke and overall carburater function.
long story short, carbs were cleaned, pilot jet cleaned with a guitar string and tested with flush. Main jets (220) and needle jets (106) brand new plus stay up floats upgrade with viton tips neddle valves. slides looked ok overall couldn't detect any warping of the bodies and bowls.
The bike fires up really well between 1st and 3rd kick. the throthle screw is just toutching the slide.
Bike is strobed at 31 degrees for aprox 3000 rpm with boyer electronic ignition.
My issue starts here, whenever I try to lift the choke the bike goes up to almost 3000 rpm like if I was opening the throttle.
Also in order to maintain 1000 rpm even with the choke on I need to have the air screw aprox half a turn out.
I can see it's running rich!
already rechecked the all setup like throttle screws, cables, carb synchronization and choke slide operation and it all seems to be like expected.
Could it be an air leak or a sign that the carbs need to be re-sleved?

Many thanks in advance!
Miguel
 
Last edited:
Migsan said:
Bike is strobed at 31 degrees for aprox 3000 rpm with boyer electronic ignition.
Click to expand...

That's a bit low for a Boyer.
"23) Start engine and time with a stroboscope to 31 B.T.D.C (28 DEG. with standard
ignition) with the engine running up to 5000 r.p.m"

Migsan said:
the throthle screw is just toutching the slide.
Click to expand...

I would expect the throttle stop screw(s) to be more than "just touching" the slide(s) so are you sure the slides are not hanging on the cables?
 
Is the choke slide free with in the slide ? my 750 has had the choke slides removed , after a tickle 1-3 kicks and it starts , I have boyer ignition, when i first got it it was set to 26 deg the pipes were searing hot and black headers , yep , got the calf , all good at 31 deg as described .Cheers
 
Shelby-Right said:
Is the choke slide free with in the slide ? my 750 has had the choke slides removed , after a tickle 1-3 kicks and it starts , I have boyer ignition, when i first got it it was set to 26 deg the pipes were searing hot and black headers , yep , got the calf , all good at 31 deg as described .Cheers
Click to expand...
Yes the choke slide is free within the throtle slide! thanks
 
L.A.B. said:
That's a bit low for a Boyer.
"23) Start engine and time with a stroboscope to 31 B.T.D.C (28 DEG. with standard
ignition) with the engine running up to 5000 r.p.m"



I would expect the throttle stop screw(s) to be more than "just touching" the slide(s) so are you sure the slides are not hanging on the cables?
Click to expand...
You were right L.A.B. the cable adjuster over the carb was to streched and I was able to lower the slide a bit more. Rookie mistake! :rolleyes: Problem sorted!
thank you very much!
 
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