CaseySmithersxs
XS650 Junkie
Can anyone tell me the dwell setting for the points? Its a 77. And correct me if the point gap os 12 to 16. Thanks!
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Dwell setting for points!?!?
- Thread starter CaseySmithersxs
- Start date
CaseySmithersxs
XS650 Junkie
Bumppppp
dwell = 93 degrees, points gap = 0.012" to 0.016"
CaseySmithersxs
XS650 Junkie
Thanks buddy!
Brian902
XS650 Junkie
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 .....
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 .....
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CaseySmithersxs
XS650 Junkie
Thanks guys! We have her running great!!!
CaseySmithersxs
XS650 Junkie
I know this is an old thread, but if my dwell meter was on an 8 cyl scale, what should the numbers be?
dirtyfuerty
10yearProject
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)
(used a digital multimeter with dwell angle and rpm settings)
On the stock XS650 points cam, a points set will be "closed" for about 90° of camshaft rotation, "open" for the other 270°. A very long dwell compared to an auto V8...
73TX650Twins
XS650 Member
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?
73TX650Twins
XS650 Member
Sorry, should 8cyl x 2, correct?
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.
73TX650Twins
XS650 Member
Thanks 5twins. This site is the best.
