Author Topic: Choke ....Manual ignition timing  (Read 447 times)

Offline Adz

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Choke ....Manual ignition timing
« on: 16.05. 2024 17:00 »
Hello,
Have a rookie question I'm hoping so one can educate me...
Choke... I am under the assumption that tight cable is normal running position. Slack cable is choke on. (seems backwards to me). Is this correct?

Engine cuts out when I turn it to normal running position. Would I be right in assuming this could be the pilot jet or an adjustment on the pilot Air screw?

Finally.... I followed the choke cable and assuming it go to the carb but it doesn't seem so. Can someone tell me what part this goes to. (see pic below)

Thanks in advance
1950 A7
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Online groily

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Re: Choke ....Manual ignition timing
« Reply #1 on: 16.05. 2024 17:44 »
All Questions are Good, so don't worry about that  . . . it's the Answers you have to be wary of sometimes!

The cable in your pic operates the manual advance and retard for the magneto and is normally on the left hand side of the 'bars.
The magneto is at full advance when the cable is slack - which is where it should be in normal running. You want to pull it maybe half-way tight to retard the sparks for starting, and there are those who like to fiddle with it when running under load, uphill, at low rpm etc to try to optimise the running state of the motor.
If you pull the lever to full retard when running along, the motor will sound very flat and may belch at you. It might even stop, especially if the magneto is getting tired. The fully retarded tight-wire position is in 99% of cases quite unnecessary as long as the timing has been set reasonably close to where it should be.
I think most people leave the lever fully advanced - ie slack - almost all the time when the bike's up and running, but maybe use a bit of retard at tickover.
It's a 'sound and feel thing' that you get used to as you do more with the beast.

The choke (air-slide) control lever would be on the right hand side of the 'bars (if there's one fitted). Pulled taut is 'off' as you say - when slack the slide is lowered to reduce the air going through the carb so makes the mixture richer. Only used, if at all, for cold starts. Otherwise, tight cable at all times and should not need touching after a minute or two's running from stone cold. Opinions vary (I'm agnostic) as to whether there's any need for the air slide anyway, given the ease of starting by 'tickling' the carb.

The plastic or bakelite cover on the magneto (on the drive side of the engine), which has a plastic acorn nut on the cranked bit, would normally have a wire off it connected to a button to stop the engine and be arranged so the wire went broadly upwards and then along the frame to a horn-push type button on the 'bars. (Just in case you were wondering what it was supposed to be doing sitting there all askew!)
Bill

Offline Adz

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Re: Choke ....Manual ignition timing
« Reply #2 on: 16.05. 2024 18:00 »
Wow OK thanks so much for taking the time to clarify.
Makes sense now.
So as it turns out I dont have a choke and I assumed the lever for the magneto was the choke.
I think my confusion began with reading the manual and it showing only 1 lever on the bars, calling it an air lever. I assumed somone had moved it from the right to the left in the past 70 years.
Much appreciated.
1950 A7
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Online groily

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Re: Choke ....Manual ignition timing
« Reply #3 on: 16.05. 2024 18:23 »
Ha!  . . . well  . . . a large proportion of A7/10s (and Trihartds and Notruns and other things) don't have a manual ignition lever because they have a so-called 'ATD' (automatic timing device) which handles the advance and retard side of things out of harm's way under the timing cover. So book references to just one lever aren't wrong for a whole range of versions of the A series - but it would be on the right as you rightly (pun intended!) say.
Bill

Offline limeyrob

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Re: Choke ....Manual ignition timing
« Reply #4 on: 16.05. 2024 18:35 »
Am I the only one who likes the AR on the left?
Doh, I mean RIGHT!!  I have the AR by the twist grip.
Senior moment.  Arrrgh.
Slough 59 GF/SR

Offline Rex

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Re: Choke ....Manual ignition timing
« Reply #5 on: 16.05. 2024 18:54 »
No, I always have A/R on the left.

Online berger

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Re: Choke ....Manual ignition timing
« Reply #6 on: 16.05. 2024 21:22 »
left. not choke haven't got one. AR lever.

Offline a10 gf

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Re: Choke ....Manual ignition timing
« Reply #7 on: 16.05. 2024 21:43 »
Here's a picture, cable movement (blue) rotates the slip ring (green), changing the points opening timing = moves the slip ring "bumps" position which opens the points contacts.


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