The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Goldy on 07.04. 2009 17:47

Title: Ignition timing
Post by: Goldy on 07.04. 2009 17:47
My A10build provides my brain with ever more questions and I am hoping that you guys may be able to help yet again. How do you prevent the magneto from rotating when fitting the drive gear/auto advance unit. Theres got to be a way , surely. ?
Title: Re: Ignition timing
Post by: snowbeard on 07.04. 2009 17:55
if you look for my post about timing with the head off, groily has devised an ingenious little bit to help with this, otherwise it's all about finesse!! (i.e. it is not an easy thing by far)

http://www.a7a10.net/forum/index.php?topic=951.0

I plan to try something similar to what he has made but without the machining tools, so likely baling wire, c clamps and duct tape  ;)
Title: Re: Ignition timing
Post by: BSA_54A10 on 08.04. 2009 08:31
Tap the drive gear home on the taper with a dead blow from a copper or led faced mallet using a big socket as a drift.
Get a pice of flat bar and bend it to fit between the teeth of the gears when you tighten the bolt.
Do not under any circumstances poke a screwdriver in between the gears as it will inevitably end up taking a corner off one of the teeth as it is tapered.
Title: Re: Ignition timing
Post by: Triton Thrasher on 08.04. 2009 09:17
I'd have to vote against whacking the gear on the end of the shaft.  Might be bad for the bearings.  I usually press it on with my thumbs.
Title: Re: Ignition timing
Post by: LJ. on 08.04. 2009 10:05
It also helps to ensure that both the male part and female part of the taper is very clean and free from oil. The cleanliness along with a sharp tap or press on with thumbs (take your pick) should ensure no slip.

... But does anyone go as far as placing the left pick up (Looking from the primary side of bike at magneto) to the left spark plug? Which I understand from somewhere that that is the proper arrangement?
Title: Re: Ignition timing
Post by: fido on 08.04. 2009 11:21
I tend to give it a tap but not too hard! In my younger days I had a disaster with a B31 when tapping the magdyno drive gear on. The magdyno is only clamped on, not bolted. My initial tap must have moved the magdyno back slightly and so the gear would then have been up against the crankcase casting. A subsequent tap broke a lump off said crankcase  *doh*.
I've never use anything in the gear teeth to prevent engine rotation when tightening the bolt. I put it in gear and apply the rear brake.
Title: Re: Ignition timing
Post by: RichardL on 08.04. 2009 11:53
Gents,

At the risk of being redundant and, without any intention of implyng that some other methods discussed in-forum are not better (Groily's clamp is quite clever, to the point it might be called "Groily's Clamp" *ex*), I am again posting the description of my timing approach. The main reason for doing so is to point to the term "very lightly tap". Using this approach, I think I only had to make two or three attempts at getting the timing where I wanted it. When I wrote the quoted paragraph, it was following replacing the ATD return springs and before starting my engine. The engine has since been started and the bike ridden, idling better than ever, accelerating and decelerating smoothly. This adds to my belief that I might have found the right approach, for me, at least. And, yes, I did clean the tapered surfaces with spirits beforehand.

Richard L.


quote author=manosound link=topic=941.msg6340#msg6340 date=1237735091]

About tightening the ATD unit without changing the timing, I have started to get a little feel for this and think I have made progress over the last time I did the timing which took about 15 tries.  First, I got sick of messing with the horseshoe washer so I cleaned the large washer (having two alignment holes) and the horseshoe washer with mineral ("white") spirits and sprayed one side of the horseshoe washer with a light coat of contact adhesive. This keeps it in place so you can concentrate on the hold-down bolt. (I don't think anyone can convince me that the possibility of this small amount of adhesive working its way into the oil as a clogging factor is a problem.) Once you have the timing set, finger tighten the bolt while applying back pressure at the points plate with the other hand. Now, with the socket over the bolt, and no ratchet or breaker-bar in it, very lightly tap the end of the socket. Now, with the ratchet or breaker, make a first light tightening of the bolt, to the extent you can, summon-up a lot of thumb strength and try holding back some of this turning at the points plate. Now, recheck the timing. If good, go ahead and finish tigtening the bolt. Recheck timing again.

[/quote]
Title: Re: Ignition timing
Post by: groily on 08.04. 2009 12:02
Does anyone go as far as setting the individual cylinder to each HT pick-up?
Yup, usually LJ! I like to have the rear (rh from primary side) going to the rh plug. Just habit I guess. But it helps if one has more than one beast to know they're all done the same way.
Agree with fido about not using things to lock the gear train. In gear, brake on will stop the engine turning until the mag pinion nut is firmly on. Once it's gripped it doesn't matter if the engine turns a bit under final tightening anyway - and always worth turning the engine a few times on the starter and then re-checking you did get the setting right.
Sympathise with the broken B31 - reminds me of the risks taken in youth when extracting mag pinions without the right pullers . . . glad I'm more grown up now. But what's worse than an ATD pinion with a dead self-extract . . . can't think of anything! I'd rather clean the dog after he's rolled in fox droppings.
Title: Re: Ignition timing
Post by: Goldy on 08.04. 2009 18:20
You guys always come up with the answers, and many of them. Thanks all very much I think  I might try the small clamp idea.