Topic: Correct dwell reading

[Doggie]

I have a '76 CB550F Super Sport. My question is about the dwell reading on my new digital dwell meter. It has 1 cyl, 3 cyl, and 4 cyl. If I check the dwell on (1) set of points, what is the number supposed to be and what cyl. number should I be on?
                                 Thanks, Doug

[lucky]

Use the 4 cylinder selection.
Read one set of points at a time.
Dwell will say either 52º or 27º

If it says 22º then you now it should be about 27º
(Half of 52º)

See what I mean?

You want the dwell to be as much as possible.
If it says 10º the you know something is wrong.

The points gap needs to be in the acceptable range
 at the SAME time that the dwell is 27º

Each set of points.

[Deltarider]

Lucky is mistaken, I'm afraid and has mixed up degrees and percentages.
In degrees readings should be:
     92-98^o on a 2 cyl. scale
or  46-49^o on a 4 cyl. scale
or  34,5-36,7^o on a 6 cyl. scale
or  23-24,5^o on a 8 cyl. scale

Easiest is to measure how Americans used to do it, in % so you can forget about scales and don't need to multiply or divide. If the selector on your dwellmeter has a position for %, it should be
51,1-54,4%.

[Muckinfuss]

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.  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.  I've never come across a percentage value specification....always degrees.  The degrees in the spec identify the arc that the points are closed.  Too high, the points gap is too small, too low..the reverse.

To help the original poster, two things to observe with your meter.....zero to minimal needle fluctuation and no more than three degrees off spec from the service manual (not all engines have distributors designs that use identical durations ie: single lobe, dual lobe etc.).  Both indicate problems somewhere in the distributor...springs, weights or ..... in general fully worn out mechanicals that need replacement.

[Deltarider]

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.

[Muckinfuss]

You get piss in your Cheerios a lot, don't you.  The reason I use a 40+ year old analog dwell meter is because I bought it new.  I have a pretty good grip on how to use tools.    If doing conversions that don't exist anywhere else is your idea of easy, then so be it.  Google dwell meter, ignition dwell, points dwell.....you won't find one instance of anything other than dwell expressed as degrees. 

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

[lrutt]

I used to use my Dwell meter on bikes. But honestly, get the point gap to .016 then do a static time with an analog ohm meter. Has not failed me in 40 years on these bikes. timing is always spot on and just doesn't seem to drift.

Now for my old cars, for whatever reason dwell seems to work best, maybe because they have an actual distributor, I'm not sure.

[Deltarider]

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.

[fendersrule]

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.

[Deltarider]

Does it matter what scale you are using?

No, not really. It's just that many years ago I saw an early digital and very simple dwell meter. It was so simple because it only measured in %. On the back of that meter was a conversion table. Simplest and best IMO.

What I do is set the point gap with a feeler gauge (choose the median number).

I'd advice to start at the wide side as points tend to narrow their gaps over time.

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".

In 'your case' that's already 2 degrees in the right direction from Lucky's 'advice'.
Sidenote: a dwell meter can detect irregularities that a feeler can't. It's like a stroboscopic timing light can detect problems with the advancer that would go unnoticed by static timing.

[TwoTired]

I have a '76 CB550F Super Sport. My question is about the dwell reading on my new digital dwell meter. It has 1 cyl, 3 cyl, and 4 cyl. If I check the dwell on (1) set of points, what is the number supposed to be and what cyl. number should I be on?
                                 Thanks, Doug

What is the brand and model of he dwell meter?
What does your meter's manual say about applicability?  Does it say it will measure a 4 cylinder engine using wasted spark accurately?

Dwell is a measure of how long the points are closed and charging the coils.  The numbers are in degrees of crank rotation, which for the SOHC4 is 190 degrees. Which is 190/360, which is 52.8% of each crank rotation, and occurs on every crank rotation.

Distributor ignitions open the points on every other crank rotation.

It is possible a digital meter could measure this accurately, depending on the design scheme used and if they accounted for spark on each crank rotation, similar to a 2cylces engine.  If the meter has a 2 cycle selection, use this.
Older meters use an internal time constant, measuring the decay of a capacitor charge vs the recharge time, and then calibrate a display to show the average voltage integrated between the point contacts.  The display accuracy will depend on if the meter was intended for a distributor system or a cycle scheme, which is equivalent to the SOHC4's wasted spark design.

You can pretty much calibrate any dwell meter to be useful on your SOHC4. 
Install new points and condenser, and carefully set the mechanical point gap to book value.  Attach your dwell meter and note or mark the indication.  That's the correct dwell for your machine and meter.  Thereafter, you can set new or used points using the dwell meter you just calibrated.  Adjust until the mark align.

Changes in dwell will effect the timing.  So, do dwell/point gap first and then the timing adjustment.  Recheck the dwell after timing.  Because sometimes the points plate movement can change the point gap/dwell if it doesn't fit into the engine case bosses perfectly, and you have to loosen the plate to adjust the timing.

I found out many years ago, that if done properly, both static point gaps and timing adjustment works fine on these bikes.  You only need to the strobe to verify mechanical advance operation.  My dwell meter now mostly just sits in the drawer, unless I have time to waste fondling it and the bike.

[Doggie]

Thanks for all the information. I didn't know I would start a "Dwell War" LOL  I just bought a new digital meter to replace my old "needle" meter because it has RPM's, temp. and more dwell settings than the one with just 4,6,8. I thought maybe using 1,3,4 settings might give a more accurate reading. I'm aware of the shim method, do to reading it on here, just didn't know the number per each setting.
                                     Doug

[Deltarider]

Do what you like. If I set my dwell at the middle value of precise 47,5 degrees (or 52,8 in percentage) the timing plates are right in the middle of their adjusting range. That tells you. Honda (and/or TEC) did their job well.  All who believe that Lucky's 52 degrees is 'spot on' are kindly invited so set their points accordingly and then report back about the left adjusting range for timing. I can't wait to hear the results.
A dwellmeter is a good instrument to detect possible irregularities that a feeler cannot. Irregularities can originate in wrongly installed or mechanically worn breaker points.
If Lucky had ment 52% he would have been correct, in degrees he is not.
What I've posted above are the correct values. Really, I can't believe that I am the only one that says Lucky is at least 3 degrees off (and 4,5 degrees off from the middle value).
I have this funny feeling that if people set their dwell according to the values I have posted above there will be far less complaints about plates being out of their adjusting range.
This forum is about communicating correct data. Thank you very much.

[RodPlunger]

I'm going with TwoTired and Deltarider on this one...

[Don R]

I may have dwelled here a bit too long. bwahahaha.

[Doggie]

Nice to end with a little "humor". I will set my points to 47.5 and then back with the results. Thanks for the help.
    Another question on my meter. Where do i connect my leads for checking the RPM's? I know where to hook them up on a car, but not a bike.
                                    Thanks, Doug

[Deltarider]

I will set my points to 47.5 and then back with the results.

Bear in mind this is the middle value of 46 and 49 and to get the gaps set at 47,5 precisely is difficult but you can get close. Good luck.

Another question on my meter. Where do i connect my leads for checking the RPM's? I know where to hook them up on a car, but not a bike.

Depends on what leads your meter has. If it has simple wires (mostly red and black) you can leave them where they are when setting the dwell. Just switch the selector from Dwell to Tach.
If the meter has an extra wire with an inductive clamp on the end, the clamp should be closed around the sparkplug's HT lead. This HT lead should be clean and free of any grease. The clamp (caution: don't drop it, they are fragile) should be closed fully. If there is no reading the clamp should be - how do you say? - turned around? This is for polarity reasons. Maybe you can give the brand and type of your meter or post a pic.                                 

[Doggie]

The meter has red and black wires.  Thanks for the info.
The meter is a MST-2800B
                                                   Doug

[Deltarider]

The meter has red and black wires.  Thanks for the info.
The meter is a MST-2800B

Isn't there a manual for the MST-2800B that you can download?

Question for all of you. I seem to remember somebody once posted a description of what part of the advancer aligns with the fixed mark when breakerpoints are opened at its widest by the lobe on the shaft. Does someone remember? That can be of great help for those who use a feeler gauge to check.

[DH]

I check mine with the plugs out and short bursts of cranking. Adjust point dwell to 47.5 degrees on the 4 cylinder scale. Install new plugs, warm it up, check timing, with a strobe, re verify dwell is good (45-49) on the 4 cyl scale and go. This is with a new Honda points/plate assy. I've made tweak adjustments while running before. I cheat but it seems to work out.

[Deltarider]

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???

[fendersrule]

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?

[Deltarider]

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?

I take it you have used the 8 cyl. scale then. If that is the case 24,5 is still OK but at the limit (it equals 0,3 mm). But... you don't want a narrower gap. Right now you're at the limit, so when points will narrow their gaps over time, you're out of spec rightaway. Meters can have some little error [?, dunno the word] however.

[fendersrule]

Remind me: the larger the dwell, the larger the gap?

[Deltarider]

No, the larger the dwell, the narrower the gap, so 23⁰ equals 0,4 mm and 24,5^o equals 0,3 mm.