Topic: using a dwell meter

[Scrubs]

I'm fed up of searching... I'm sure there is some info in the vaults somewhere but I cannot find anything...
Can someone tell me simply how to use a dwell meter (or multimeter with dwell measuring function to be precise)

Where do I connect the test leads to take the reading from?
and what number should I be looking for as a reading? (74 cb750)

I have settings for 4/6/8 cylinders. so knowing the correct read outs for one of those settings would be great.

Thanks

[Bob Wessner]

Hmm, tried searching myself. I'm guessing you found no hits at all? I tried several searches; dwell, points, 750 and Honda. Nothing at all. I think the search function is not working. I'll mention it to Glenn.

[Scrubs]

Hi Bob,

I got a few hits, and got some results, although it wasent the usual style of results - it looked as if it was re-routed
to search through google - but out of the results it did show, where the keyword dwell showed up. I found no straight
forward instructions of how to use the dwell. I am assuming I just put it accross each point terminal, but don't know
what readings I should be looking for.. Might be a good addition to the FAQ.

I've just installed new points.. When the F mark of #1/4 is lined up should the points of 1 & 4 be just opening?
or is that 3 & 4? at the moment they are both wideopen at all F marks because I havent set it right.

[Bob Wessner]

Can't help with the dwell meter, I use static timing only. This has come up a couple of times (can't explain why it can't be found though  ). Maybe someone can write up something for the Ignition FAQ.

My search via the forum search function yielded nothing at all with all the terms I listed. I wasn't redirected to the Google search. When I tried the Google search, I found, as you did, lots of hits but nothing definitive.

[Bob Wessner]

The forum search function (not to confuse with the new Google search) seems to be working again. I found this relevant thread. There are others if you just do a search on "dwell."

http://forums.sohc4.net/index.php?topic=20087.0

[Steve F]

When I use my dwell meter, I use the 8-cyl. scale and the reading should be 23 to 24.5 degrees, this is based on the Clymer manual which says 2-cyl scale=92-98 deg., or 46-49 deg. on the 4-cyl. scale.  Since my meter apparently only reads the 8-cyl. scale correctly, I go with the 23-24.5 deg.
Hook-up is simple, black lead goes to the ground, and the red lead goes to the same connection as the condensor.
Adjust the point gap until you get the correct reading, lock 'em down and then set your timing.

[TwoTired]

Dwell is the number of degrees of crankshaft rotation that the points are >>closed<<.

Honda specifies this as 195 degrees.  Or, a little over half of a single crankshaft rotation, at 195 out of a possible 360.  You could actually use a degree wheel and a small test light to determine the exact dwell your points are set to.  But, what of Dwell meters?

Dwell meters are electrically connected across the point contacts, and meter deflection is powered by the voltage present across the points when they are >>open<<.  Thus, dwell meters give an interpretation of dwell based on the inverse data.  Their scales are then calibrated using assumptions about the motor to which they are to being attached.  Most of these are wrong for the SOHC4, which fires on each rotation.  A standard 4 cylinder engine with distributor points ignition fires a single cylinder on every OTHER crankshaft rotation.  They expect to actually deflect the needle at an inverse ratio using 720 degrees, and the points are closed for 4 cylinders firing events.  No wonder there is confusion on how to use them on the SOHC4!

So, what to do.  As accurately as you can and with a brand new point set, adjust the max point gap with a feeler gauge that is midpoint between the min and max spec. (.012-.016) or .014 inch.  (You could actually do the degree wheel/test light thing I mentioned earlier, too.)  Attach your dwell meter and spin the engine.  Make note of where the pointer is on your meter's scale.  On my cheap Dwell meter, that's 47-49 degrees on the 4 cylinder scale.

Now you can set the dwell using your meter, calibrated to your bike, and the style of ignition it has.

Cheers,

[markjenn]

Good post.  Honestly, I think on a SOHC the best bet is just to set point gap statically with feeler gauges and then time with a timing light (which allows you to do both idle and advanced timing) rather than attempting to use a dwell meter.

- Mark

[Gordon]

When setting the points on my 550 I use a feeler guage for roughly setting the gaps, and then do exactly as Steve F. described with my dwell meter to fine-tune them. 

[Scrubs]

Thanks lads, That helped alot and I managed to get it sorted! 

[alltherightpills]

Attach your dwell meter and spin the engine.

So dwell is not set with the engine running?

[TwoTired]

Attach your dwell meter and spin the engine.

So dwell is not set with the engine running?

Sounds like a trick question.

Setting dwell is done by changing the point gap.  This can be accomplished regardless of engine crankshaft motion.  You still have to position the crank to get the points rubbing block on the high point of the points cam.  Reading dwell is done with the crankshaft spinning and power must be applied to the points via the coils.  It's easier if the engine is running, but you CAN set dwell with a strong battery and the starter motor.

Cheers,

[alltherightpills]

I didn't think it made sense for the dwell meter to really work without the engine running, but when you said "spin the engine" I thought you meant turn the crank using the 23mm nut on the points plate.  I just used a dwell meter for the first time last weekend, and I wasn't sure if I did it right, but it sounds like I did   Thanks for the clarification.