Timing/Points question

I am putting my 69 S back together and have a question about lining up the contact breaker cam. In the factory manual it shows lining up the advance weights pivot point with something...I'm not sure what! Is there an easier or simpler way to get the contact breaker cam in the right spot to static time it?

Here's how mine went on at TDC. I'm not sure if it makes any difference 180 the other way or not, it may. There's a mark on the cam that doesn't show up. Then static time it with a light, buzzer, ohm meter or voltmeter. You'll know if it's out, or you can switch the point wires, I guess you're using the 12V coils with separate circuits for each coil like original?



Dave
69S

Yes, everything is as original. I can't tell from the picture, where is the notch in the breaker cam?

Well, I and you can't see it because I've got the washer on it that holds the aau fully advanced, see the weights? If you don't have the washer, you'll need it, I epoxied 2 washers together. You should be able to tell which way the aau goes, it's one way or 180 the other. The points will open upon firing the plug. Put it on one way and check which point is opening, remember the aau rotates anti-clockwise, see the arrow at the left? Normally the left contact breaker is connected to the yellow and black wire and is used for the drive side cylinder. If you figure out where the cam mark is, let me know and I'll mark it in the picture.

Make sure your aau is not worn so much you can't get consistent points gap, that's what happened to mine, and the timing wanders all over the place, but it ran. The cam gets loose on the shaft. Someone came up with a bushing to put in there, but it requires machining.

Dave
69S

I'm going out on a limb here and saying it should be like this. With the mark on the cam pointing just to the left of straight up. Looks like that would be opening up the black yellow contact next if it's rotating anti-clockwise.

You can see how worn my cam is on the shaft.



Dave
69S

I am going to give it another shot tomorrow after work.

Work? What's work?

Dave

Long lead = L jug = white. Yellar short lead R jug. Place engine so correct rotor mark is on correct 28-32 full adv mark on factory dial or one made on stator. The loosely put on AAU and slight snug mount the breaker plate centering in slots. Next with test light one lead on fin the other on breaker spring, jiggle the AAU til light comes on. Settle AAU, with it held full adv. a bit more stable on taper and try to get light lit. Turn engine till lights and note rotor-stator mark degrees. Do same with other points to get sense which one off the most. Then center all the breaker and gap setting adjustments. Knock AAU lose and diddle to light again when crank at proper fire positon. Then turn until cam opens points the most, the small slot mark, then set gaps to .015". Then turn engine until lights and check marks then diddle each point to light closest to rotor/stator indecation. At this point can put plugs on head to see if they spark and check marks when it just does.

Then try to start, if back fires more whole plate retard a tad. if noting might be too retarded so creep up tiny amount adv to feel for starting ease. If run out of whole plate slot range, guess what, knock loose the AAU again and fine tune till happy. If AAU too worn will not idle back and may back fire it stays stuck adv.

Well I seem to have the points opening for the correct cylinder close to TDC however I can't seem to get the light bulb to come on around 28 TDC. I'll have to wait until I can start it and check with the timing light I guess.

You had best get the points opening with the cam fully advanced around 28°, or it may be real hard to start or kick back. Then it's time to strobe. Power off and ohm meter worked for me, not that I use the AAU anymore.

Dave
69S

Its tricky to set up points and easy to set point to fire on wrong jug, so leave rocker covers off to verify that jug has both closed on compress so both rockers are loose rattle that side. Combat's are 28'-ish max advance by book but mine seems happy a degree of so more advanced and no kick backfire starting. Timing must be pretty darn close or will beat you up trying to kick off. Lots of back and forth with indicator light till both points light up as rotor mark close to 28' stator or dial mark. You have to mostly nip up AAU and Point plate stable each time you check for the light of spark point. I'd guess a perfectly good point system should stay unattended for 10-15 k miles, then suspect time to buy electro ignition if can't find AAU or rebuild it. Running issues on road or at home with points means more mystery of condensors, AAU, points burnt/worn etc to keep in mind,beside carbs and wires and plug too of course.

I got it....or at least I think I do. I'll let you know when I get ready to start it.

We need the video showing the sparks flying off those points.

Dave
69S

I tied and did video Trixie points sparking in the dark but good matched condensers make sparks so short and ultra blue wasn't dramatic enough to post.
Making nice sounds much better video to shoot for here.

Hi,
An old and well hacked subject I know but....on the question of worn cams.
Aquired my" low mileage" 1972 (non combat, drum brake option) 750, just last month. First job, check points gap
workshop book says "set points gap when the nylon heal of the breaker points is aligned with the small mark on the cam,(highest lift position)"
Well i got news, my cam has a slightly higher profile bump opposite this mark on the cam, I suspect this is due to wear.
just for now i have set the gap as per book on both sets of points ( lower bump), loosened the aac off its taper and set the timing as described.
Q. Will the slightly higher section on the cam have an affect on the overall timing . (remembering that i have set the gap and timing etc. on the lower profile section of the cam (probably only a few thou difference in gap).

Will kick her over tomorrow and see how smooth the old girl runs.
Thanks

Oldrider said:

Q. Will the slightly higher section on the cam have an affect on the overall timing . (remembering that i have set the gap and timing etc. on the lower profile section of the cam (probably only a few thou difference in gap).

Click to expand...

Adjusting the points gap basically alters the dwell angle (the number of degrees the points remain closed) and I believe the dwell is more critical than the actual points gap.

You could always try removing the high spot from the cam with a small oilstone?

not much can wear the cam profile down [not by the oily plastic points lifters] only the inside as another reason AAU don't last too many decades. Seems like i remember another slight hump in profile but set points as manual and all worked well as should.

Thanks hobot,
I finally got to pull the guts out of timing thing, took out the AAU for a closer inspection.
The bumps are the ramp up and the drop off for the points .
There is a lot of wear but not unmanageable i hope.


Well all back together now with new plugs and leads
Went first boot and sounds awesome.

Never had a bike anything like this beauty.

Thanks for comments and suggestions ..will post again, maybe i can help another rider when knowledge comes.

These bikes will run amazingly good despite the dwell angle wandering all over the place, which also makes the timing wander around. I would suggest you make a brass bushing to put between the cam and the spindle or get a shop to do it. Then keep it greased up frequently with distributer lube.



Dave
69S

DogT's repair/upgrade shows where the cam mainly wears, on the inside so cam wobbles. Oldrider's AAU shows the worn slack to take up. Its such a booger to reset points if the AAU removed to grease it so I've been using Lucas oil treatment, thick STP like thickness. By removing the cam end bolt I can pull the AAU cam out to expose the inner shaft to squirt oil on then just put the bolt back in and head right out. There's other things that wear out too. The springs get slack so cam don't return to full retard so idle jumps up or fails to settle down at stops. The slots in cam plate get worn where pins ride over 2000 rpm and tend to hang up on slow up. I had show stopper pulling into work last year, at home found a spring peg on plate had broken off to jam the points up. About only craft more a maintenance headache might be an old wooden sail boat.