Misc: Ignition Need Advice, can't keep an idle (intermittently) approaching or at a stop with New Amal 276's

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Folks
I found fault in retiring my original 276's for new 276's. Neophyte move--old 276's "3" throttle valve and top notch needle position for new 276's with "4" throttle valve and 2nd notch needle position. I noticed the bike ran lean...hesitated why I did the compare. I did not give Coventry Spares the throttle valve spec because I knew not.

(All of this got started when I went to a dual twist grip throttle and new cables which I am happy with)

I have a "3" on order from coventry. Question: how does one know beyond trial and error to figure the right # throttle valve? Could you do a compression test and correlate to throttle valve # required?

Thanks

Mark
Hi Mark, These AMAL related documents may provide some help
 

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  • Tuning guide cutout.pdf
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  • Carburettors__the_things_you_have_always_wanted_to_know.pdf
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Mark Stephenson

Well Known and Active Forum User
Non-VOC Member
A bit of AMAL History
Martyn...thanks so much. I can't wait to read these!!! Amal ships the first doc with their new carbs that I ironically bought from John Healy:). The tuning guild will take some further reveiw. Look forward to it.

I am excited to see what the "3" will do on my new 276's. and use these guides to tune away.

Mark
 

Mark Stephenson

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Non-VOC Member
Retail is retail and johns prices would be almost the same as burlens. Shipping in the us from conventry is much, much faster and cheaper than the uk. Shipping speeds would only be exsabated by COVID.
I have bought the carbs from John. Pricing comparable. Appreciate the service. Shipping from UK dodgy and he puts Cookies or Chips in each package:). Have "3" Throttle Valves coming on Monday!!!
 

Mark Stephenson

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Non-VOC Member
Putting the original 276's on the shelf to run with new versions. The new 276's are functionally similar but not identical. I noticed the original "3" throttle Valves were snug, too snug in the new 276's by way of example. Can't wait to try the new 276's with the correct "3" throttle valves and noted Rear carb had a "two notch" needle position. I set them both to "one notch" needle position. All the best, stay safe. mark
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Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Air leaks as mentioned above by Greg can give some strange tick-over problems because the vacuum when the slides are closed will likely pull in air if there is a leaky joint. A small leak isn't so likely to show up as a problem when running with the throttles open as there is less restriction so lower vacuum.
Re: heat build-up. I don't have a problem with the tick over long idling periods. I use a new type BT-H magneto but have VM28 Mikuni carburetors fitted so not a direct comparison. I have the carburetors mounted using rubber radiator hose so I'm wondering if that reduces heat being conducted back to the carburetors.
There must be lots of people using standard carburetors that don't have a tick-over problem so likely checking all the little things will improve things.
Hi Eddy,

I am contemplating fitting a 28 or 30mm Mikuni to my Comet but have NO experience with setting them up. Are you able to share with me the configuration, jets selection etc?

Many Thanks,

Martyn
 
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