Topic: Problems with standard ignition, especially with centrifugal advancer (CB 550)

[w1sa]

If the full advance is pegged at about half (as indicated), and the 1-4  idle timing appears correct, then it would also appear that the advancer mechanism is not providing the required range of movement between idle and full advance...........as previously indicated by 'Scottly'.

When you look at the base plate mounting position (photo by OP), it appears to be in a more 'retarded' position than for normal range set-up....... that, combined with the statement that 1-4 are OK but 2-3 are retarded to the T mark...........and that's with 'full advance' adjustment to the 2-3 points plate (see photo)...!!......and, best 2500rpm advance is about 15deg total..!!??

Per Scottly's original advice........check the advancer mechanism!.....inspect for faulty parts/installation and service/lube for full, smooth, free range of movement ........before you worry about shimming or other possible faults/variables.

A simple (additional) test of movement range/servicability, is to rotate the advancer fully
(to simulate full advance @2500rpm) and set the (points) timing to the full advance mark(s).....when set, and checked against the corresponding idle timing, the idle timing should be very close to the required 'F' position at idle.....

[bollingball]

(An alternate method is to peen the plate in the post area to make a zero tolerance fit.)

First off I have never had to shim or do any thing to my bike (78 750K). But if I did I would like to know what you are talking about in the red. I can not picture it in my head what or where you are peening or how this works. I am thinking you mean peen the plate on the bottom side next to the post?? But it seems to me a shim would do something different all together.

Thanks Ken, for the kind words.

If the main points plate is not retained tightly while the three screws are loosened, the plate can move laterally within the mount posts.  The point cam on a running engine pushes against one point spring and then alternately the other.  The springs transfer force from the point cam lobe to the points plate.  Without the tightened screws to hold the plate steady, the plate moves laterally within the post restraint bounds, adding/subtracting the plate's back and forth movement to each point's gap as the cam rotates.  Changing the point gap also changes the timing.

You must loosen the three screws to adjust the plate's rotational position while doing a dynamic timing adjustment.  To maintain consistent point gap, you must also ensure the main points plate cannot allow the point gap to change.  Unless you remove the point springs, a static check will away find the plate pressed against a retainment post by the point spring and you won't imediately observe any plate sloppiness when the screws are loosened.

To be certain the gap will not change during dynamic timing, either the plate is shimmed to eliminate any lateral (vs. rotational) movement of the main plate, or the plate itself is modified dimensionally so it can ONLY rotate.  If the plate moves laterally to the right,  the 2-3 points loose some gap making them "run out" of adjustment.  Moving the whole points plate to the left increases the 2-3 point gap while decreasing the 1-4 point gap.

Identify/locate the plate's interface position with the motor's mount post sides.  Best to do this with a bare plate with components removed.  At each post location on the plate peen the metal (smashing it between hammer and anvil) to slightly reduce the plate thickness in the mount area.  The metal will then extrude or flow outward increasing the circumferential dimension in the areas of the post retainment.  If done carefully, the plate will fit into the post retainers and only allow rotational movement.

The skill come in with deciding which of the three interface point needs to be grown for your particular points examples.  Worn rubbing blocks or poor point build geometry can require biasing the plate extrusion growth greater at one post interface location.  I would recommend doing the shim trick first, to find where the most growth is needed to have both points attain proper adjustment timing.

After a point plate is peened to fit properly in the motors posts, I suggest it be "married" to the motor.  New points would be transferred to the "married" plate when those parts need renewal.

I know this post would be better with pictures.  I simply don't have the time or inclination to make a pictorial document.  Sorry.

Cheers,

TT
Thanks no picture needed you described it well I finally after so many years can understand what needs to be done and why if I were to run into this.
Again Thanks
Ken

[englishwheeler]

TT
I did what you said and was able to get my points extremely close to perfect with my ohm meter. I was able to fit a .007" shim on the lower left post. I am still nearly maxed out on the adjustment of the plate, but was able to get it.
As this is a customer bike, I'm still thinking about a dyna system for maintenance ease for him, but I'm glad you shared this information. It helps me with my other 550's.
It was
 Too late to fire her up last night, but I will do it today and report back.

[TwoTired]

TT
I did what you said and was able to get my points extremely close to perfect with my ohm meter. I was able to fit a .007" shim on the lower left post. I am still nearly maxed out on the adjustment of the plate, but was able to get it.
As this is a customer bike, I'm still thinking about a dyna system for maintenance ease for him, but I'm glad you shared this information. It helps me with my other 550's.
It was
 Too late to fire her up last night, but I will do it today and report back.

Just a follow up.  I hope all understand that with .007" plate "slop", as the engine is running with plate mount screws loose, that .007 was changing the point gap settings of both sets by that amount while the engine was running.  Ideally, you would insert the shim before setting the point gaps, and then proceed with the timing adjust.

To reiterate, the point gaps or dwell determines the coil saturation time, which Honda determined was adequate for the stock coils, plug caps, etc., and included expected point system deterioration between 3000 miles maintenance checks, as well as combustion atmospheric conditions regarding altitude, temperature, humidity, barometric pressure, etc.   The system is robust enough to handle most abuse and misuse by those tampering with the design parameters.

I wonder what the original tolerance specs for the Honda points plate was back in the 70s when the engineers still has purchase approval authority, instead of just the accountants or salesmen of today?


Be aware that the anemic charging system (550 moreso than the 750) will be further taxed by the addition of a Dyna S ignition trigger, due to the fact that it does not mimic the dwell time of the standard point sets.  The standard point sets charge the coils over 195 degrees of crank rotation, while the Dyna is in the range of 270-330 degrees; about 75% more energy is absorbed by any coil installed because of this.   The tolerance of this is dependent on type of use.  Battery recharge of a healthy charge system will be effected less during freeway cruise and consistent mid -RPM operation.  But, in-city persistent use of idle will tend to deplete the battery, particularly so if the lighting is kept on.
I note that many times a Dyna-s installation is closely followed by charging system/electrical system refurbishment.  This probably wasn't true when the bikes were young.  But, they no longer are young and all the connections have an average of 30-35 years exposure to the elements and its oxidation qualities.

Food for thought...

[lucky]

"But try to keep the gap as small as possible because the gap gets wider over time."

umm?i think youll find as the rubbing block wears theyll close up a little or a lot lucky.

Yes you are right. I had it mixed up. Sorry. The gap would get smaller.
If the points cam stays lubricated the amount of wear is negligible.