Author Topic: Ignition timing  (Read 4786 times)

Online RichardL

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Re: Ignition timing
« Reply #15 on: 10.09. 2008 08:31 »
Mine is auto advance and the timing is set with the mechanism jammed at full advance. I suppose that with manual advance exact tnot as critical with the automatic advance. Believine this, I must have tried a dozen times before I got itto what I think is right. Yes, it does change ith tightening, but I must be careful what I, as I can't recall if all engines used the tapered pinion shaft or if earlier models use a woodruff key. For the tapered shaft, it is essential, I believe, that the pinion get set on the taper by using the least torque necessary before tightening the small screw through the center of the points block. I tried tapping the pinion onto the shaft with a mallet, but that is risky and, I think, tended to move the point a little on its own.

Must get going. Bye.

Richard
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline snowbeard

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Re: Ignition timing
« Reply #16 on: 10.09. 2008 17:07 »
both mags I've been into (a 54 that's on it and the 57 that came off) had the woodruff key on the points plate, so I didn't really bother loosening that.  both of mine had the tapered pinion for the drive gear, and I think I actually used the little bolt on the points to hold everything steady on tightening, but don't do that, it's too small and delicate.

it took me at least six tries too, eventually I learned how much it would slip and tried to counter it.  hence having to recheck it after a few times.

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Online groily

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Re: Ignition timing
« Reply #17 on: 10.09. 2008 22:47 »
Methinks it might be worth - if the timing pinion slips while the nut is being done up - lightly dressing the taper on the armature shaft and the cone in the pinion on the bench to make sure they are both burr-free and clean. Also, a very clean thread (worth alway running a die down it) and a very clean nut, preferably a new one. A little cleaning, fine emery paper will do, can go quite a long way, even though the thing doesn't look much different for it. Ideally, you should be able to press the pinion on the taper gently by hand to the point where it engages enough to take nut and spanner (wrench) without going for a walk. In which happy case it's perfectly OK to hold, gently, the cb centre bolt with a 4BA (or 1/4AF)  box or socket spanner, while the pinion is lightly pushed on at the other side and a very clean and free-running nut run up the thread to hold it. It's hard enough getting the pistons and points in the right places by whatever means, without having to guess what error will introduce itself while you do the thing up. Although some people do reckon a light tap works, I prefer not. Even a gentle whack can make the thing bounce, losing the setting at the cb end in the process. Plus put a new tiny burr on both male and female taper. But I agree, it's a miserable job, trying to do one thing up without disturbing another, which you can't see properly while you're doing it.
 
Sometimes I think it would be good if mag pinions were keyed to their shafts and a dot provided on the pinion to align with the adjacent one, as per cams. Wonder if anyone has done that? The mag would then almost certainly be model- and marque-specific. But, boy, would it make it quick and easy to put together. The downside would be lack of ability to compensate for wear on the cam ring etc. Oh, and the problems that could follow on from an armature rewind! Maybe they outweigh any possible gain, so shan't be attacking anything with sharp weapons any time soon . . . . just day-dreaming really.
Bill

Online RichardL

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Re: Ignition timing
« Reply #18 on: 12.09. 2008 05:21 »
Yep. As I've said before, it couldn't be any more awkward trying to set the smallest possible opening of the points while the cam rider rides up on the steepest portion of the cam.

One thing I did to make myself less crazy, while making multiple attempts at timing, was to spray the backside of the horseshoe washer with some spray adhesive so it would stop falling off every time I loosened the pinion.

Richard

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Offline snowbeard

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Re: Ignition timing
« Reply #19 on: 12.09. 2008 05:42 »
horseshoe washer? *dunno2*     


I think my tach drive nut is right on the timing gear itself, I didn't have a washer when I replaced mine...  but it is a manual advance, so just a steel and fiber gear on the pinion...  maybe a washer would help eliminate some slipping tho?!
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Online groily

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Re: Ignition timing
« Reply #20 on: 12.09. 2008 10:55 »
no horseshoe washer with a standard manual set-up- it's on the ATD under the head of the centre bolt and goes against the washer with 2 locating holes in it which is under that . . . As Richard says they flop about a bit! But not sure quite how tacho-drive goes as haven't got one.
Bill

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Re: Ignition timing
« Reply #21 on: 14.09. 2008 16:36 »
Had to redo my ign timing this a.m., when I found that the new points fitted to my SRM recon magneto had been fitted at the absolute limit of adjustment, and there was no way of getting a bigger gap than 8 thou without trying to modify the mounting for the fixed point. (it swivels on the centre bolt fixing and is held fast by a small screw in a slotted section of the plate below the point). Lousy item, which I didn't really want anyway, but I was told that the backplate and points I supplied couldn't deliver the same timing on each cylinder. Strange, I thought, if the cam ring was serviceable (which it was) and the bearings were new (which they were by then), but OK, you know more than me, replace as necessary etc. Anyway - replaced the thing this morning with an old brass Lucas one off another spare mag, put a new set of points on it, and things have been transformed. Better in every way, including they're adjustable!.
But the thing is - the mag pinion went on without force or any slip / risk to the position of the cb unit at the other end, which didn't even need holding during proceedings.
Good to see while I was in there that the mods I had to make to the toothed belt dynamo drive conversion (steel taper and centre for cheesy alloy pulley whose taper self-destructed in a matter of a few hundred miles) were holding up well and that the belt had not stretched in several thousand miles. All's well in the end - but that's 2 SRM things I haven't been that chuffed with, and 3 if you count the supply of allen screws instead of longer studs for attaching the alloy sump plate with drain plug, which might just be me being faddish about screws into aluminium. Silly little things which I will mention next time I'm on the phone to them, but they've absorbed some time fixing/improving stuff that shouldn't really have needed it.
Bill