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.

[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.