The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: michael snellin on 02.09. 2014 15:44

Title: Ign timing ??
Post by: michael snellin on 02.09. 2014 15:44
Hi, every one its just that i have now finished the bike and its now time to try and start it up( try will be the word ) can some one tell me the correct way to time it up i know it its 5/16 to T D C on the comp stroke its the mag side of things that is a bit of a grey area, also would it be the right thing to do just to kick it over with the sppressor caps off. get the oil round the big ends
Title: Re: Ign timing ??
Post by: Topdad on 02.09. 2014 16:51
Hi Mike, two school of thoughts re timing (who said here we go again ? ) I'm in the basic camp others are in the more modern approach  ie timing disc and timing etc.  Has you need a starting point ( no pun intended ) heres how I do it and later if you wish you can always fine tune.  Firstly I take off the rocker box covers and I assume youve still got the outer timing case off . kick the engine over or use the back wheel ,in gear, plugs out and establish TDC  check valves for tappets rocking  turn back engine til approx 5/16 " 9 (i insert a pencil suitably marked ), next magneto, check points gap and set to 12 thou (points clean) , check both sides open same amount , turn mag until points just loosen ,I use a fagg paper ,when that starts to slip holdit ,if manual advance  pull lever full advanced ,if auto wedge open springs giving max advance ( don't drop in oiltank.. sorry Richard ) slowly offer the unit upto the mag shaft and without moving it tighten nut on unit ,if manual do same . TAKE OUT WEDGE . finally check points and if no movement get ready to start ,if it's moved do it again, re the oil kick until it returns to tank or push bike plugs out or combination of both , hope I haven't forgotten anything but sure if I have you'll get info from someone else , it's not as bad doing it asithis sounds best of luck BobH.
Title: Re: Ign timing ??
Post by: Greybeard on 02.09. 2014 17:44
I timed my engine while it was on the bench with the head off. I made up a bar with a long bolt with locknut tapped through its centre that I bolted down across the cylinder face with my lockable bolt sticking down the bore. I used my dial guage to get the correct BTDC point and set the stopper bolt/screw to prevent the piston from rising any further. This meant that I knew the pistons were in exactly the correct position. I gapped the mag points, wedged the advance & retard device open and then instead of a cigarette paper I used my multi-meter set to ohms across the points. I can't remember the range but the meter showed a different reading; points closed, points open. When points were just opening, (is that right?) I nipped up the points retaining bolt, removed ARU wedge etc. I don't know if a battery and bulb would work if you didn't have a meter.

PS. I retested several times to make sure I'd got it right.

I know a fag paper is only a few thou' but electrical continuity seemed a more accurate method to me.
Title: Re: Ign timing ??
Post by: Triton Thrasher on 02.09. 2014 18:08
Don't use suppressor caps and don't kick it over with the HT leads disconnected.
Title: Re: Ign timing ??
Post by: duTch on 02.09. 2014 23:31

  It doesn't matter which side you time, so long as procedure is consistent with that side, when you determine which side is on compression (hence Bob taking off the rocker covers?), also look in the maggie pickup hole, and check which one has the slip-ring brass contact in view (doesn't matter, but I think consensus is the top one goes to right???)
 To determine TDC, I (and others) get it close, then turn the crank one way so the piston is down a bit and measure down plughole, then turn it the other way the same distance (this is where a Musky degree wheel is handy), and split the difference.

  I also found that if you take the split pin out from the cush spring nut, you can use a length of stainless welding filler rod as a pointer to a reference point on your case ( on mine, the hole 'happens' to be at 90˚ to the crankpin, so is a bit awkward)
 Don't forget to replace the split pin..!!!!

 When you're done,it's been known for some to store the wedge safely in the oil tank, but not recommended.. *smile* 
Title: Re: Ign timing ??
Post by: beezermacc on 04.10. 2014 07:09
A few tips to save time..... 1) You don't need to take the tappet covers off to find compression. Put the bike on the centre stand, take both plugs out and turn the engine over slowly with the rear wheel and 4th gear engaged whilst holding your thumb over the left hand spark plug hole, you'll feel pressure on the compression stroke.  2) If using a depth gauge rather than a timing disc time the bike on the left cylinder then you can watch the depth gauge and the points at the same time. 3) You don't need to remove the pickups to see the brass bit of the slipring to find which cylinder is firing because the heel of the points is consistent with the brass part of the slipring. i.e. the heel of the points is closest to the pickup which is firing, provided the tab at the back of the points hasn't been messed with - sometimes people put a new tab 180 degrees from the old one when it gets damaged.

My general procedure is as follows.....
Put bike on centre stand, remove both plugs, find TDC roughly on compression stroke feeling pressure on thumb then drop in depth gauge to confirm, (on manual advance bikes make sure cam is fully advanced), wedge the ATD and fit loosely to the armature, check tdc again and rotate the engine backwards to your btdc timing mark on the depth gauge, rotate the points so that the heel is pointing left and the points are just starting to break (I use a breaker light but fag paper is fine!), push the ATD onto the taper and tighten, remove the wedges and tighten up a bit more, fasten left plug lead to left pickup and right to right....... job done.
Title: Re: Ign timing ??
Post by: RichardL on 04.10. 2014 16:08
In my own experience, I always recheck the timing (with the wedge in place) after tightening down the ATD. I am reasonably assuming that Beezermacc has a better touch with the tightening than I.

Richard L.
Title: Re: Ign timing ??
Post by: bsa-bill on 04.10. 2014 17:51
a better touch

That's what it comes down to really, back in the day guys in garages were doing this all the time so got a feel for the drag of the fag paper, and those here that deal with points on a regular basis will have the same, for the rest of us it's trail and error, and nothing wrong with that either really, it's not as if it's so difficult to repeat a tad one way or the other, but a timing disc just quickens the process.
a fag paper is about a thou, you can get a strip of 1 thou feeler gauge stuff (about a foot of it), I cut an inch or so off and use that bit until it gets creased to much
Title: Re: Ign timing ??
Post by: RichardL on 04.10. 2014 19:55
In my last struggle to get my bike running, I must have timed it 20 times (at least). Other things were wrong that I did not recognize. I talked about those too much in another post but, briefly, loose cam ring and off-center cam-ring housing.

One of the frustrating things, for me, when finding where the fag paper slips is the fact that it occurs right on the upslope of the lobe and makes the points want to ride back down the lobe before you can tighten the ATD. I found that if I snug up the ATD enough to create friction to prevent this, the points soon become too tight to rotate, as I use a 1/4" box-end wrench on the center screw. (In another thread, years ago now, someone commented that I must have a very tight center screw. I took that to heart and pay close attention to how tight it's getting.) I've now taken to using a slim wood wedge (made from a door-jamb fitting wedge) between the brass post and the cam ring. This allows me to adjust the friction just enough to avoid riding back down the slope while allowing free adjustment. If I am the last to come up with this, that wouldn't surprise me. If others are doing similar or have variations, I'm curious.

Richard L.
Title: Re: Ign timing ??
Post by: muskrat on 04.10. 2014 20:36
G'day all.
It's been 15 years since I've had a magie on my A's but I still time a few of my mates bikes with them. I have an earth brush screw with the brush replaced with a timber dowel. Get the points to the right spot with one hand  and tighten the screw (just enough to hold the armature) with the other. When putting the ATD or fixed gear hold it against the cam gear in a clockwise direction to take up any backlash and push it on.
Title: Re: Ign timing ??
Post by: duTch on 04.10. 2014 22:41

  That's a good idea Musky..... *bright idea*
. I found that if I snug up the ATD enough to create friction to prevent this, the points soon become too tight to rotate, 
  Richard'  I was wondering why you were 'rotating the points', until I realized it was the armature combo. ...  *doh* 
Title: Re: Ign timing ??
Post by: RichardL on 05.10. 2014 02:17
I considered saying "armature", but it's really the points that are the object of focus. No?   *dunno2*