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Old 12-14-2012, 06:16 PM   #1
CanadaBiker OP
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Joined: Sep 2012
Location: Southern Ontario, Canada
Oddometer: 278
Figuring out my old Dwell meter?

My father gave me his old Snap On dwell meter and timing light. I remember using it on my Charger when I was younger. My tach is broken on my newly acquired R100, and I plan to get it fixed, but in the meantime I was hoping to use the dwell meter to check dwell & rpms.

The meter has 8 cyl & 6 cyl buttons, plus it looks like you can do the math for a 4 cyl on the 8 scale. There is also a button for 1000 rpm and below, and 1000 rpm and above. So, there has to be some way for this to work, if I do the math? Should I use the 8 cyl and divide by 4 for rpms? Does the R100 have a 'wasted spark' system?

And for dwell, do I use the 8 cyl and divide by 4 (so 78 divided by 4?)

The meter has a positive clamp and a negative clamp, plus a yellow clip. Do I put the clamps on the battery and the yellow clip on the black side of the coil?

I swear I thought I used to know this stuff?

Any help would be awesome. Thanks!

CanadaBiker screwed with this post 05-27-2013 at 11:06 AM Reason: spelling
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Old 12-14-2012, 06:49 PM   #2
disston's Avatar
Joined: Mar 2011
Location: Silver Spring, Md
Oddometer: 10,218
Yes the red and black leads go to the battery and the yellow is to the right side coil points wire. It is a wasted spark ignition system, all Airheads, whether electronic or points ignition, are a wasted spark system.

For the math I think you might have to go to Snowbum's site. He's one of the few that can do math. I have used a dwell meter but I have to go look that up every time so I'm pretty sure it's there.
Never memorize something you can look up.
---Albert Einstein

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Old 12-14-2012, 07:01 PM   #3
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Joined: Sep 2009
Location: Melbourne, Australia
Oddometer: 2,071
An eight cylinder motor fires 8 times per 720 degrees of crankshaft rotation.
An airhead fires twice in 720 degrees.

Therefore an airhead turns through 720 degrees 4 times before it has fired 8 times.

Multiply the indicated RPM for an 8 cylinder motor by 4 for the correct 2 cylinder RPM.

An eight cylinder motor fires once per 90 degrees.
An airhead fires once per 360 degrees.

If the meter shows a duty cycle of 67% or a dwell angle of 60degrees for an 8 cylinder motor, this is equivalent to 240 degrees for a 2 cylinder motor.

Multiply the indicated dwell angle for an 8 cylinder motor by 4 for the correct 2 cylinder dwell angle.
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Old 12-15-2012, 12:34 AM   #4
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Joined: Aug 2007
Location: Easton Wa
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From Anton's site that has dwell info.
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