Topic: Correct dwell reading

[fendersrule]

Ah, Gotcha.

So you typically want a slightly smaller dwell when possible because it will continue to narrow as the points wear over time, as long as it's still in spec.

24.5-25 seems perfectly in the center of the suggested tolerance (I can't remember if it's 24.5 or 25 as I'd have to test again). But if you can get away with it, go with something maybe 23.5. I'm just going by guessing here, but if 24.5-25 is a .35mm gap (about .014 inch), going to 23 dwell is a .4mm gap (about .016 inch), which really is the maximum limit. Seems like 23.5ish would be IDEAL on a fresh set of points....It's near the maximum but it's not right at the maximum.

I know with Honda twins that it's common practice to set it in the center to give you enough flexibility for when you adjust the R-side points gap, so I've always been setting them dead in the center when possible. It looks like this is still a good practice with SOHC fours, but you're getting at how to slightly tweak it so that it stays in spec longer.

Thanks Deltarider, you da' man. I feel like with this info I have about mastered setting points on SOHC fours!

LUcky, 27 dwell would be way too much! The gap would be really small, probably not even in spec.

[andrewk]

You want as much dwell as the ignition/timing/points can handle, as this creates the strongest spark.

I use 24 degrees on the 8 cyl scale of my old 4-6-8 dwell meter.

Age of the points doesn't matter as much as the quality of the point set. 24 degrees on an old set would be the same on a new set- the measurement is the duty cycle.

With the Honda twins, you split the timing gap because the slack in the valve train affects ignition timing.  With crank driven ignitions like the SOHC4, there's no need to do this- you can balance the points perfectly using the plate, there's no need to split the difference unless you're working with junk points.  On a new OEM plate, everything is pretty well centered, so that is a good starting point if you're starting/assembling from scratch.

[TwoTired]

If the dwell increases with use (points closed for longer duration), then the rubbing block is wearing faster than the point contacts.  I suggest you find a better, slipperier lube for the points cam or check the points cam for galling, grooves, or other grindy bits.

I had to replace te pont cam on pone of the CB550s because of this.

The dwell is normally far more than sufficient for general use.  It becomes more critical around red line, when there is minimal time to recharge the coils.  If you are "cheating" with correct dwell.  You probably won't notice unless you are using red line a lot.

[DH]

I check mine with the plugs out.... Adjust point dwell to 47.5 degrees on the 4 cylinder scale.

You certainly cheat. Please teach us how to set 'dwell to 47.5 degrees on the 4 cylinder scale' with the plugs out???

Been a while since I did this, here's what I think I did
From what i've read, total dwell is 94-98 degrees when read on a 2 cylinder scale.
When read on a 4 cylinder scale,  dwell is 47-49 degrees,  per each set of points.
When read on an 8 cylinder scale, dwell is 23.5-24.5 degrees per set of points.
My meter doesn't have a 2 cyl. scale so I use the 4 cyl scale.
The meter is an anolog type. It will read with engine cranking and kill switch in run position. I take the plugs out first, then the engine cranks very smoothly. Replace them when the points are close. Honda points and plate assys. seem to be close enough to start the engine,
and that may have a little something to do with it. I've actually made fine adjustments while the motor running. End result tho, is what counts, so correct dwell AND timing
before removing the meter and strobe. Someone may blow this method out of the water.... but I've done it.

[DH]

Delta, I use the method I mentioned above. Actually, I would say I find the best dwell at around 24.5 not 25. Is this correct?

We should start our own little club Fenders

[Deltarider]

You want as much dwell as the ignition/timing/points can handle, as this creates the strongest spark.

That's academic. It's one of these things that, once said by someone in an academic mood, is echoed over and over again on the internet.
The truth is on our bikes you will not experience the difference.

[andrewk]

You want as much dwell as the ignition/timing/points can handle, as this creates the strongest spark.

That's academic. It's one of these things that, once said by someone in an academic mood, is echoed over and over again on the internet.
The truth is on our bikes you will not experience the difference.

I think you'd argue about ice cubes being frozen or not.

"Echoed over and over on the internet" is not my zone.  I work on dozens of points bikes per year.  Weak dwell causes problems, enough said.  You might read one line farther and make a note of the dwell setting I recommended.

My advice is based on DOING.  When the (my) ignition breaks up at/near red line, and changing the dwell ~1.5 degrees clears it up, and changing it back brings back the behavior, I know I've found my culprit.  But hey, whatever floats your boat- my bike runs perfect so it's working for me.

[lucky]

I still use a 40+ year old dwell meter and there's only degrees.....that's all I've ever known, and I believe Lucky is spot on with this.

Well, actually he is not. If by 52 he means degrees, he is at least 3 degrees off, resulting in a gap too narrow and people might run out of range to adjust the timing.

There are digital meters and perhaps they read in percentages, but I don't see how that would be of benefit since any service manuals I've ever had speak to the number of degrees that the points are closed....the dwell

If and I repeat if your meter offers the % option it is easier to work with. Let me calculate for you: 47,5^o is how much % of 90 degrees, 95^o is how much % of 180 degrees? Get the picture? % is easier to work with for you can forget about the number of cylinders > less chance for mistakes.

 

I've never come across a percentage value specification....always degrees.

 
I have seen both and often enough both in the same specification list. As a matter of fact the garage manuals of all the cars I have owned gave both. If not, the calculation is very easy to make as shown above. Maybe you have missed how many times this 'what cyl scale do I have to use' question is asked here. 
Now that we have established that in % duty cycle should be 51,1-54,4%, those with the % option can just select that position without any multiplying or dividing to do and don't need to ask this cyl scale question again. Hope you can forgive me for that.
Maybe you would like to set your dwell at 'spot on' 52 and report us back if there's any range left for timing.
Thank you very much.

It is not an exact thing. A couple degrees one way or the other is ok as long as the points are in the "range " also.

It is DEGREES. Degrees of crankshaft rotation.

[lucky]

As far as 52 degrees versus anything else, always go by what's spec'd in the manual....not an internet expert

Can you inform us what manual prescribes 52 degrees for a CB500/550 or CB350/400 Four for that matter?
Please set your breaker points gaps at 52 degrees and report back about left range for adjusting the timing. We love to learn.

Connect the swell meter on one set of points.
Depending on the dwell meter it will read fifty something degrees OR... 27º
APPROXIMATELY.

Just do it and you will see how it works.
I figured it out when I was 17 years old, and there was no internet.

[lucky]

Does it matter what scale you are using?

What I do is set both point gaps with a feeler gauge (choose the median number in the center of the tolerance).

Then hook up a dwell to it and see what both sides are dwelling to. Pick the average number of the dwell. In my case it's "25". Set both points to the same number. Re-check with a feeler gauge, and both sides should be spot on.

I use dwell for consistency and not for actually initially setting the point gap.

I then dynamic time to the advance marks. The idle dynamic doesn't concern me unless I'm "way" off from the "F" mark. If it's a few mm, no worries. If it's way out, then it's time to delve further into a problem.

Excellent description!!! Perfect.

[Muckinfuss]

+1     Dwell is an audit of what "is" and a diagnostic tool.

[Deltarider]

+1     Dwell is an audit of what "is" and a diagnostic tool.

Whatever, as long as people know that on unmolested bikes you can do the timing by adjusting the breakerpoints gaps and so avoid unnecessary loosening/adjusting the plates (which is far more difficult).

[fendersrule]

Delta, just threw on a brand new NOS TEC set.

23.5 dwell on the dot I found to be ideal. Dead on in the allowed tolerance.

With the stupid Diiachi points I had, I was using a larger dwell. Crappy geometry, must be.

Holding the Diiatchi points up to the TEC points already shows why they are simply not correct. The Diiatchi points have more of a steeper angle.

Bike timed perfectly in less than 5 minutes. Dead on the mark at idle. Dead on at advance. Runs absolutely perfectly now.

It's amazing what a nice set of OEM points can do for you.