Topic: using dwell meters

[eldar]

OK I got a dwell meter this winter. I stumbled around and found out how to hook it up. It read about 2000 rpm at idle, which seemed very high. I looked here in past posts and found I had to divide the reading which shows I was idleing about 1000 rpm. Hey pretty good idle there.

My question is, do I have to do this with the dwell reading? Do I have to multiply the reading or divide it or take it at face value? It isa 6/8 cylinder set up which means that for dwell, you double the value. Well if the meter was correct, I was only around 52 when dwell is suposed to be like 80 - 90.

Any tips from those having used dwell before.

[Bodi]

You can check the dwell with a static timing light, try to mark the amount of rotation that the points are open. If they're open for 1/4 of a crank turn, your dwell is 75% (closed for 3/4 of the time).
If you set the points gap correctly, that sets the dwell. Unless the cam lobe is worn down dwell will be what Mr. Honda wanted.

[eldar]

So really then, setting the gap at the low end of the range will increase the dwell then. Oldfart recommends setting the gap to .012 or so to maximize dwell time.

[amattel]

My manual says Dwell shoud be set to 92-98 degrees ( 2 cyl scale) or 46-49 degrees (4 cyl scale) or 23-24.5 degrees (8 cyl scale)
If you look on your meter scale there should be 1 or more lines to read on based on number of cylinders it is reading.  Of course even though we have four cylinders, we only have to spark impulses, so a direct reading would be on the 2 cyl scale with 4 and eight adjusted accordingly.

Adam

[Bodi]

The definition of contact ignition dwell is: 'the number of degrees of distributor rotation with the points closed'.
Hmmmm... which distributor would that be?
The Honda lost spark system is somewhat equivalent to a 2-cylinder engine with a distributor. One "distributor rotation" is two turns of the crankshaft and each 360 degree full turn of the crank is 180 distributor degrees. Thus 90 degree dwell would have the points closed for half the turn.
Increasing dwell isn't necessarily good. You need enough closed time to ensure the coil saturates, Kettering systems characteristically give weaker spark at high RPM as the coil gets less and less time with power appplied. At high RPM you also need to leave the points open long enough to let the spark discharge, the spark isn't instantaneous upon the points opening because of the capacitor which essentially delays the spark a bit so that the points are open enough that there's no spark across them.
If you're reading 52 I would assume this means actual 104 degrees dwell and your points gap is a bit small, not horribly small though. If it really IS 52 degrees then something is badly amiss in the points area.
The points, plate and engine are imperfect so the points sets are never - maybe occasionally by accident - exactly 180 degrees from each other. Usually one sets both gaps to spec and then sets the 1-4 timing, after that the 2-3 timing can only be adjusted relative to the 1/4 by adjusting the 2-3 points gap... so only very rarely is the 2-3 points set to exactly the "spec" gap (or dwell angle). Really anal tuners will try to have one points set a bit wide and the other a bit tight.
If your points cam is in good shape, you can set the points gap via dwell. If you know gap vs dwell on a good cam you can tell a worn cam by measuring both and comparing.
For a street engine I would set the 2 gaps as close as possible to spec and see if I can get the timing correct... OK, honestly, I would install an electronic ignition and forget what dwell means.
You can use the dwell meter to check for points problems, it should stay constant from idle to redline. Futzing around at high RPM usually means the points are bouncing off the cam and need to be replaced - worn out springs.

[eldar]

well I will double check things but point gap I think is set at about .012 or .011 which is on the minimum side for my year. I will probably have to open them a little but I adjusted them before I knew how to read my meter sicne it did not come with any kind of refence to motorcycles.