Position of maximum points gap?

[Its been a long time]

Setting static timing this afternoon. I have a question about points gap please. (cam chain tensioner set statically first, engine rotation by hand).

My eyesight isn't what it used to be and I'm not confident I have set the points gap at the best position on the cam. I have gapped the points to 0.015" to allow for a bit of heel wear. So just checking the collective experience here if I may.

I have the points just opening at the "F" mark. With a wrench at 12 o'clock and the rotor in the F mark, if I turn the wrench 180 degrees anti clockwise (cam rotated 90 degrees) I should be confident I have the best measurement position for points gap?

Thanks for helping an old fart with bad eyes!

 

[Jim]

Sounds like that would work. Your "theory" is solid enough, but I've never looked to see if that's actually where the high point of the lobe is.
If you have access to a dwell meter... it's gonna give you your best point setting.

The book listing for points gap is a "one size fits all" setting. Truth is, that just gets you close to the correct dwell. And dwell is actually the more important and accurate setting.

 

[Its been a long time]

Sounds like that would work. Your "theory" is solid enough, but I've never looked to see if that's actually where the high point of the lobe is.
If you have access to a dwell meter... it's gonna give you your best point setting.

The book listing for points gap is a "one size fits all" setting. Truth is, that just gets you close to the correct dwell. And dwell is actually the more important and accurate setting.

Unfortunately I don’t have a dwell meter. I think in the morning I'll go through it again as I described. Thanks.

 

[member43148]

If no dwell meter is convenient such as in my own case too, how about a timing light ?
I’ve always used a timing light to confirm timing at least.

 

[Its been a long time]

If no dwell meter is convenient such as in my own case too, how about a timing light ?
I’ve always used a timing light to confirm timing at least.

I intend to use a strobe light once I have it running, for sure. Presently I'm carrying out static timing using a multimeter so that the engine should start once I'm ready to give it it's first start.

 

[Jim]

Another method I've used in the past. This isn't gap dependent, so it's a bit easier and will generally get you about as close as any other way that doesn't use the dwell meter.

1. Set the main point's plate to the center of its adjustment range. Then do the same for the left (lower) points plate... center of adj range.
2. Rotate the crank until the right (top) points set opens, then rotate the crank backwards (clockwise) about 90°. Then rotate until you're dead on the fire mark.
3. with a 12v light, adjust the right points gap until it just breaks open (light on). You can rock the crank back and forth to verify it opens just on the fire mark.
4. Do the same for the left (lower).

This will get you close enough to run. After it's running, you really need to put a timing (strobe) light on it for the most accurate timing.

This procedure ignores the gap and dwell callouts... but it get's you pretty damn close on the actual timing. And if you think about it, setting just by gap ignores the dwell callout anyway... and setting the dwell ignores the gap callout. This method gets you closest to the correct timing... which is actually the more important value.

 

[Its been a long time]

Another method I've used in the past. This isn't gap dependent, so it's a bit easier and will generally get you about as close as any other way that doesn't use the dwell meter.

1. Set the main point's plate to the center of its adjustment range. Then do the same for the left (lower) points plate... center of adj range.
2. Rotate the crank until the right (top) points set opens, then rotate the crank backwards (clockwise) about 90°. Then rotate until you're dead on the fire mark.
3. with a 12v light, adjust the right points gap until it just breaks open (light on). You can rock the crank back and forth to verify it opens just on the fire mark.
4. Do the same for the left (lower).

This will get you close enough to run. After it's running, you really need to put a timing (strobe) light on it for the most accurate timing.

This procedure ignores the gap and dwell callouts... but it get's you pretty damn close on the actual timing. And if you think about it, setting just by gap ignores the dwell callout anyway... and setting the dwell ignores the gap callout. This method gets you closest to the correct timing... which is actually the more important value.

In fact, that's pretty much what I'm doing. First set the gap then checking the static timing, top set of points then bottom set.

I'm going to check using my F mark plus half a crank rotation method on each set of points too just to satisfy my curiosity.

Once I have the thing actually ticking over, I'll be using a strobe lamp. I need to check out the advance unit functionality because it has been monkeyed about with by me and has one Chinesium and one Yamaha spring installed.

 

[5twins]

The dwell angle on these bikes is about 90° (93°± 5°). That's how long the points "dwell" in the closed position, allowing the coil to charge up for the next spark. That means the points are open for almost 270°. The middle of that range would be 135°, so maybe rotate the engine a bit more than 90° to get to the maximum points gap?

If you plan to stick with the points, getting a dwell meter is a good idea. It's the easiest and best way to gap the points, and the only accurate way to gap used points. As points wear, they develop pits on them, and that's where the spark jumps between. You can't measure that with a feeler gauge. The actual gap will be bigger than what you're measuring between the points faces. For this reason, it's a good idea to set used points at the lower end of the gap spec, around .012".

 

[Its been a long time]

The dwell angle on these bikes is about 90° (93°± 5°). That's how long the points "dwell" in the closed position, allowing the coil to charge up for the next spark. That means the points are open for almost 270°. The middle of that range would be 135°, so maybe rotate the engine a bit more than 90° to get to the maximum points gap?

If you plan to stick with the points, getting a dwell meter is a good idea. It's the easiest and best way to gap the points, and the only accurate way to gap used points. As points wear, they develop pits on them, and that's where the spark jumps between. You can't measure that with a feeler gauge. The actual gap will be bigger than what you're measuring between the points faces. For this reason, it's a good idea to set used points at the lower end of the gap spec, around .012".

Thanks. That's very helpful.

(The jury is out on whether to switch from points to electronic ignition. I need to get this bike running first, shouldn't be long now.

My quite limited personal experience is that aftermarket electronic ignition systems tend to be much less reliable than OEM systems. On the other hand, good quality points and ignition system capacitors are not as easy to find as they once were and are getting expensive when you do find them.)

 

[Its been a long time]

Had time this morning to pick this up again.

For those interested in setting points gap after fitting new points, I can confirm the following method works. Setting the points gap as follows ensured I had about the best setting I could manage. There could be a better way, but this worked for me -

With the rotor timing mark on F, fit a wrench on the crankshaft nut with the wrench at 12 o'clock. Turn the wrench anti clockwise until it is between 4 and 5 o'clock. Check which set of points is open, it could be either set. At the open set I used 0.015" feeler gauge on new points. Set the gap. 0.015" allows a bit for heel wear. Having set one set of points, rotate the wrench anti clockwise again by one full turn to between 4 and 5 o'clock. Set the second set of points.

Having done the points gap, set the static ignition timing for the top set of points, then the bottom set of points.

Lightly oil the two felts pads and close up the points cover.