Ariel Owners Motorcycle Club

Hi Martin

Is this the system you have installed?

https://burtonbikebits.net/bbb/wp-conte ... W61495.pdf

If so it instructs removal of the auto advance at step 3.

If you can give more details / photos of your system I'll give it some more thought.

Regards Mick

Hi Mick

Yes that’s the system I’ve fitted. I did think the instruction to remove the AR unit couldn’t possibly mean an A10/Huntmaster - since if it was removed, there would be an empty hole and nothing to drive the timing!

I definitely don’t want to dismantle the AR unit to disable it (in case I or anyone in the future wants to revert to magneto ignition). So maybe there is a way to lock it in place?

I guess the combined AR advancing and the unit advancing as well means the ignition is triggering (when above 2500 revs) at something like 44 degrees BTDC - which would give loads of knocking and ‘dead’ power? It doesn’t feel like that when driving along - although it doesn’t leap forward, I’d put that down to 35bhp and a 65 year old machine!

I can’t be the first person to have installed this system on these engines, so maybe a call to wassell to enquire would be an obvious next step.

I’m the meantime, is there any way to lock the AR?

Cheers

Sporting BSA A7s and A10s had manual magnetos and used a plain
gear to drive it. This is part number 67-0540 - I think - and with an
appropriate nut should replace the A/R in the Huntmaster should
the need arise. They are a bit more of a pain than the A/R in that
you'll need a separate extractor to remove it.

I have a manual magneto gear (fibre gearwheel) to suit, should this be of interest to you to try out, you can pm me for further details.

Hi Martin

Struggling to visualise what you've got / done.

Do you have a dummy magneto which houses the trigger coils and magnetic rotor? if so I think you need to disable the AR, and the manual option mentioned by Will is the 'off the shelf' way to achieve this, (Draganfly have them for sale). I'd avoid trying to lock the AR mechanism for fear of the means failing and becoming a hazard in the timing case and the risk of associated damage. Good AR units are thin on the ground so look after the one you have, they are only going to get scarcer!

Of course, my assumption could be wrong, in which case more details of your installation would be required.

Regards Mick

Hi Mick

Yes - dummy magneto (head is triangular like the K2F, houses a coil and some sort of solid state magnet set up. Near billet design bought from drags. The Wassell coil trigger is static installed inside that circle, and then a timing marked rotor bolts into the AR so that bit whizz’s around. Set the engine to 34 def, and supposedly line up the trigger to the pointer inside the coil. I think the whole problem is right there. If I’ve held the AR at fully advanced, when it’s released and all bolted up, the rotor passes the timing mark (now) 5-10degrees later, so the engine at startup is triggering at 24-28 degrees - too far retarded? - so the burning fuel is super-heating the exhausts at idle. As it revs up, there’s a sweet spot where the AR is advancing the timing, but so is the ECU! At some point it runs sweet. Beyond that sweet spot it’s now too far advanced collectively and it’s all getting very noisy - and feels ‘heavy’. So I think you are all correct - the mismatch of mechanical AR and electronic one is sending all a bit haywire.

Looks like that superb tip (and part number) for the replacement gear is the way to go.

I’ve got the original magneto safely boxed away. I guess it’ll be joined by a pristine AR unit too….

Hi Martin

Not quite:

You've timed it as for a bike with a mechanical AR so the timing is correct for revs up to the point where the AR starts to function, however, as you ALSO have an electronic AR system installed this will be added to the effect of the manual one. So at tick over the timing should be spot on, as you open the throttle the timing will be advanced by twice the degree required. I'm surprised the bike isn't pinking or spitting back through the carb, which leads me to wonder if the timing was / is retarded and hence your coloured exhausts.

I wouldn't ride the bike until you've reduced your AR systems by 1/2.

Regards Mick

Mick

Since day 1 of this great fun restoration, your advice on every topic has been immeasurably helpful.

Your explanation of this last gremlin is equally bang on and very clear. Bike firmly parked while a plain gear is sent for.

With many thanks, All the best

Martin