Simple question regarding ignition contacts

Hi again, sorry for this simple question but I find it kind of hard and very sensitive to get the timing just right; so here's my question:

When you sit on the bike in "riding mode" there is a left hand cylinder and a right hand cylinder. When you look into the stock contact breaker unit there is a set of contacts on the left and on the right, which one controls which cylinder?

I just want to be 100% sure, before I have another go at adjusting :|

Ghostbuster said:

Hi again, sorry for this simple question but I find it kind of hard and very sensitive to get the timing just right; so here's my question:

When you sit on the bike in "riding mode" there is a left hand cylinder and a right hand cylinder. When you look into the stock contact breaker unit there is a set of contacts on the left and on the right, which one controls which cylinder?

I just want to be 100% sure, before I have another go at adjusting :|

Click to expand...

The manual doesn't really show a standard and any advise maybe 180 degrees off. Depending on who and how it was last assembled will determine which is which. Your best bet is to check the lead from point to coil to be sure.

That being said, If it is running now, I am not sure it matters.
Setting the gap is redundant. Setting the opening point or static timing is another. You must remove the center bolt and replace with a special washer so as to hold the auto advance unit in a full advance position. Put the piece of paper in the points and bump the motor around with the back wheel in forth gear. At the exact point that the piece of paper will not hold is where you check your 28 degree BTDC reading. This is your static timing for points, and, of course, is dependent on if your marks are accurate in the primary side.

Ok, I did it a little opposite. I locked the crankshaft in 28deg, with at special tool (only works on MKIII I'm told) Then I adjusted the contacts until i could make a "control lamp bulb" blink, when i turned the little cam to fully advanced.

The reason I asked was that I was wanting to make "fine"-tuning with a timing gun.

How dangerous is it if the two contacts are not equal, it can't be good if one cylinder fires at 28° and the other at 30° right?

Ghostbuster said:

Ok, I did it a little opposite. I locked the crankshaft in 28deg, with at special tool (only works on MKIII I'm told) Then I adjusted the contacts until i could make a "control lamp bulb" blink, when i turned the little cam to fully advanced.

The reason I asked was that I was wanting to make "fine"-tuning with a timing gun.

How dangerous is it if the two contacts are not equal, it can't be good if one cylinder fires at 28° and the other at 30° right?

Click to expand...

If your points are not gapped equally there will be a slight variance.

From my 68 workshop manual.

'Normally the LEFT contact breaker set in the distributor (to which a yellow and black wire is attached) is used for ignition on the DRIVE SIDE cylinder.'

It probably only matters on the early bikes with 12V coils. I think Mick in his DVD says the same.

Dave
69S

pete.v said:

The manual doesn't really show a standard

Click to expand...

http://britmoto.com/manuals/Manuals/750_man.pdf

Section C38.8:

The contact breaker points leads are black and yellow or black and white and this feature allows the operator to check which set of points are feeding which coil and cylinder. The factory standard arrangement is for the left coil and cylinder to be fed by the yellow/black rear set of points.

Click to expand...

Ghostbuster said:

The reason I asked was that I was wanting to make "fine"-tuning with a timing gun.

How dangerous is it if the two contacts are not equal, it can't be good if one cylinder fires at 28° and the other at 30° right?

Click to expand...

Starting up with a discrepancy of a few degrees between cylinders to do the final strobe checking/adjusting won't do any harm.