Author Topic: Magneto Habits?  (Read 233 times)

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leon bee

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Magneto Habits?
« on: 14 March, 2021, 07:53:26 »
Hello everyone. I've gotten my 53 B33 running well after a long layup. New piston, rings, new .020 overbore. I had the bike running some years ago with a lot of things cobbled up and a tired magdyno. Now I have an allegedly rebuilt ebay mag which does seem real strong. But I don't fully understand it.

I've only ever owned one other magneto fired bike; an HD Sportster years ago. On that machine you retarded to start, then put her back to advance and went on. Is that how you guys do? On this B33 I retard to start, (tight wire retard), and then it is very sensitive to advance it. Took me a while to figure this out- if I just advance all the way after starting she runs and then peters out just as if she were running out of fuel. No knocking, pinking, wheezing at all, just runs down and dies. At first I thought she needed a choke, quickly manipulating throttle might keep her running.

Then.....I realized it all seems to be with the advance. Advance less than all the way she'll run till warms up and I'm ready to go. Going down the road I can advance all the way and she runs and sounds good. But pull in to the garage it'll die unless I retard it a bit.

Sorry to be so wordy about this, but really curious. Like many of us, it take me a while, a few tries when I time the engine by setting that pinion. I might think it's just too advanced, but when starting her cold there is no way it would need retarded more than my present setting provides. I've not had dry enough weather yet to go for a long ride.

So, main question is: do you guys retard to start and then just advance her all the way? Or do you ease up on it? And do you mess with the lever while riding? Any other thoughts are very welcome. Thanks!

Calum

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Re: Magneto Habits?
« Reply #1 on: 14 March, 2021, 09:02:17 »
My B31 tends to like the timing retarded roughly half way on the lever to start (mine is a 1953 build, taught wire advance as original). Retard it any further and I can't get it to go. I've not once had it kick back so it might be too retarded full stop? Runs and goes well though when fully advanced. After I've started it I advance it pretty much straight away. Once warmed through I can retard the ignition to a nice bob-bob-bob slow tickover. I'm not totally sure the timing is spot on as I haven't checked it yet - it's a job on the list before I get back out on it but it seems pretty good (I already reset the points and plug gaps, cleaned the pickup etc).
Do bear in mind I've only had it a few months so really not sure on its 'behaviour' yet!

Rog1

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Re: Magneto Habits?
« Reply #2 on: 14 March, 2021, 09:44:19 »
I have a 1953 M33, so it's the same engine. I half retard it to start, once running I put it back to full advance and leave it there. I've tried adjusting the lever going up hills, but it doesn't seem to make much difference or it just reduces power slightly. I set the timing a few hundred miles ago and it's pretty much spot on. it sounds like your timing is out.

leon bee

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Re: Magneto Habits?
« Reply #3 on: 14 March, 2021, 20:34:08 »
Yes, sounds like I probably have it set too advanced. Trying to learn before adjusting it. Thanks, guys.