Dwell setting for points!?!?

5twins

XS650 Guru
Top Contributor
Messages
25,043
Reaction score
22,943
Points
813
Location
WNY
Well actually, when you set the dwell, you are setting the gap. I gap them by eye then get them exact by using the dwell meter. I never touch points with a feeler gauge anymore.
 

Brian902

XS650 Junkie
Messages
810
Reaction score
21
Points
16
Location
PEI Canada
And I use one of these to set the timing.
.
 

Attachments

  • IMG_1702.jpg
    IMG_1702.jpg
    218.8 KB · Views: 868

5twins

XS650 Guru
Top Contributor
Messages
25,043
Reaction score
22,943
Points
813
Location
WNY
I suppose a little discussion about dwell, what it is, and how it applies to our 650s is in order here. First off, the dwell value for the 650 is given in the back of the factory shop manuals in the electrical section. However, if you're looking for "dwell" or "dwell angle", you won't find it. Yamaha labels it as "Cam closing angle". And it is given as a "range", not one set number. This corresponds to the measured gap range of .012" - .016". The spec is given as 93°± 5°. That would be 88° to 98°.

Now, a little explanation about what that number you're seeing on your dwell meter actually means. A dwell meter really doesn't measure your point gap or opening time, it shows how long the points are closed, or "dwelling" in the closed position. For this reason, the reading you get will be inversely related to the points gap. In other words, a larger number indicates a smaller points gap. Also, most of the meters you see and use will be set up for car use. They will have settings for 4, 6, and 8 cylinder motors. To use one on a 2 cylinder motor, you have to do a little math.

On a 2 cylinder motor with one set of points, you simply divide the 2 cylinder dwell value in half to read it on the 4 cylinder scale. With 2 sets of points though, you have to divide it again and use 1/4 of the 2 cylinder value. So, on our 650s, you will be looking for 22° to 24.5° on the 4 cylinder scale. 22° will give you the largest in spec gap so that's what to aim for. This should give you the longest run time between service intervals and the need to re-adjust.

If you are determined to keep your points then you really should have a dwell meter. It is the most accurate way to gap them and the only way to accurately gap used ones. Used points develop pits on their surfaces and that's the spot where the spark jumps. You can't measure between those pits with a feeler gauge. The gap you think you're setting is actually larger than the feeler gauge is indicating.

On most of the old fashion dial type dwell meters, the scales start at about 20°. Since that's right about where our 650 readings are, these old units are difficult to use. I recommend you get a new digital read-out type. Here's a shot of the dwell meter hooked to my 650 when I had the single point conversion installed. That would use half the 2 cylinder dwell value, or 44° to 49°. For largest in spec gap, I would shoot for 44°. Here I got 44.1°, pretty good I think .....

2MFpSdA.jpg
 
Last edited:

dirtyfuerty

10yearProject
Messages
10
Reaction score
14
Points
3
Location
Ireland
Correct dwell angle is 22 to 23 degrees its a twin so 45 degrees halved is 22.5 degrees
(used a digital multimeter with dwell angle and rpm settings)
 

73TX650Twins

XS650 Member
Messages
24
Reaction score
52
Points
13
Location
Minnesota
2 sets of points, does this look correct? First pic is right cylinder, second is left. Assuming I multiply the 8 cyl reading x 4?
EDBC84A8-08A5-42C2-9F0E-538E80DB98D7.jpeg
8868C983-BA1D-40D6-933B-1290910ED9A3.jpeg
 

5twins

XS650 Guru
Top Contributor
Messages
25,043
Reaction score
22,943
Points
813
Location
WNY
Yes, that looks about right. The 8 cyl. reading of around 11° x 2 will give you a 22° 4 cyl. reading. The actual 650 spec of 93° ± 5° (88°- 98°) converts to 22°- 24.5° when read on the 4 cyl. scale. The numbers you see are inversely related to the gap size. In other words, a larger reading indicates a smaller gap, smaller reading means a larger gap. I try to shoot for the largest in spec gap (smallest reading) because points usually close up as they wear. This will let them remain in spec the longest.
 
Top