Setting timing with strobe.

[Nurse Julie]

I'm trying to teach myself how to set the timing with a strobe light. I can't get 1&4 to time up, I run out of adjustment on the plate and the firing timing for 1 & 4 at full clockwise is firing just before full advance. I've tried it on 2&3 and they are spot on. What an I doing wrong 🤔🤔🤔🤔

[paul G]

Have you set the points first !
If I remember correctly Julie 1-4 should be done first then 2-3 but the points must be done first.

[fogrider]

You beat me !, I was just about to say get both points set  with, hopefully, the plate in the middle of its' marks.  Then strobe 1&4 first.
I have a vague recollection, possibly from my CB750 days, that certain makes of points are gits to set. Maybe someone else is aware of that.
Regards, Terry,
East Yorks

[K2-K6]

If you've got the 1/4 points at wide end of tolerance you may not have enough plate movement to set timing correctly.

Set them to minimum and see what you get then.

It can be awkward to get everything in complete range, accepting gap compromise to get accurate fire point may be needed.

[Nurse Julie]

Thanks Chaps, I will start at the beginning again.... Every day a learning day ☺️☺️☺️☺️

[Nurse Julie]

Well, I'm a lucky Lady. A chap that I know popped in for a cuppa this morning and I told him my tales of woe. He's an old boy who knows soooo much and is willing to share and help. Within 2 minutes, he had it all set up and strobed and it was absolutely spot on. I had set the points gaps in the correct order and with the correct gaps and set the timing but..... I didn't take any account of dwell 🙃🙃🙃🙃. I had set everything up as per the manual, which assumes all parts you are playing with are very new with no wear. Once he had set the points gap to about 0.00000001" of a thou, everything lined up perfectly and the bike started instantly and now rides as fast as a rocket ship. The Old boy said don't use the manual, throw it out of the window. I was pleased though that I had vaccumed the carbs and they were spot on where I had bench synced them to originally. A good learning experience for me.

[MrDavo]

I can’t explain why after decades of bike riding, but I don’t understand dwell, in the same way that I don’t really understand the structure and rules of music, despite decades of listening to it.

Can someone explain what the old boy did, and why it was different to setting the bike to just opening the points at the timing marks?

[Nurse Julie]

I can’t explain why after decades of bike riding, but I don’t understand dwell, in the same way that I don’t really understand the structure and rules of music, despite decades of listening to it.

Can someone explain what the old boy did, and why it was different to setting the bike to just opening the points at the timing marks?

Well it won't be me explaining it Dave 😁😁😁. It's electrickery and a dark art combined which I don't stand a cats chance in hell of explaining. All I know is that it worked.

[K2-K6]

Dwell is just the time the points are closed for (the period that the coils are charged) in crankshaft degrees.

That's really the critical time period of the ignition system that's of interest as it's governing how much energy is stored. If you make the points gap larger it reduces the dwell as it just gets up the cam ramp sooner, and so gives the coil less time to accumulate energy.

Essentially you accept whatever points gap you end up with (within reason) to get the dwell and timing point accurate as that's what the ignition performance is based on.

Points gap only becomes a problem if the condenser can't absorb the spike as the points open, making small points gap problematic as the spark jumping across them (easier if gap is small) doesn't give clean switching to the coil to bang the HT current out on time.

[fogrider]

Did you make a note of the dwell angle he settled on ?   If the bike now goes that well, check the dwell and record it for future use !
Regards, Terry.

[fogrider]

Strange differences indeed !       Most 4 cylinder cars  with a standard  .012" to .015" points gap are set around 50 deg dwell.  I  have used my old 4 cyl dwell meter on a few 4 cyl hondas' and 25 on the 4 cyl scale is 50 on the bike. That's a good figure for spark production and always works a treat. My 550f is set at that and I'm very happy with the performance

Always interesting to hear what others are doing though.
Regards all.

[Seabeowner]

I think the actual dwell on the Hondas is about 50% (180deg or 45 on a 4 cyl scale) Correct me if I'm far out.
What I am not clear on is that the dwell is set to give the inductive coil sufficient time to fully "charge" and also not over tax the coil.  But is it set so this is sufficient time at maximum rpm? (3.3ms at 9000 rpm) And therefore an overly long time at lower revs.
Also are electronic ignitions set so the give a fixed charge time at all rpms? So power drawn will be a lot less at idle say.

[K2-K6]

The relationship of dwell to the effect it has is quirky and worth looking at.

Dwell being geometric and represented as an angle,  but the effect it has on the coil is purely time based.

When you set dwell at X rpm it gives the coil a time period to charge based on that rpm. But as you increase speed of crankshaft the dwell is still a constant geometric angle, but with the time base now decreasing.  The coil just gets less time to charge.

As most points fired cars are going to see a maximum 5000 rpm generally it doesn't get too short.

But these fours see twice that,  with attendant reduction in coil charge time. Effectively you need to set dwell as much as you can get away with for these bike engines, hence the difference in views above.

It's one area that electronic systems can control more effectively,  they generally are designed to produce a dwell they control as the same time throughout the engine rpm range, triggered at timing for both on and off coil cycles independent of geometry.

[K2-K6]

I think the actual dwell on the Hondas is about 50% (180deg or 45 on a 4 cyl scale) Correct me if I'm far out.
What I am not clear on is that the dwell is set to give the inductive coil sufficient time to fully "charge" and also not over tax the coil.  But is it set so this is sufficient time at maximum rpm? (3.3ms at 9000 rpm) And therefore an overly long time at lower revs.
Also are electronic ignitions set so the give a fixed charge time at all rpms? So power drawn will be a lot less at idle say.

Crossed over with you there while typing 

They accommodate error with coil resistance on these systems, using 5 ohms to avoid overheating them at low rpm but sufficient to cope with charge rate at the higher end as I understand it.
As example, if you put 3 ohm coils on there they'd overheat at low rpm use (ignoring system switching requirements) but may be ultimately better at continuous high rpm when needing less time to fully charge them.

[fogrider]

Seabeaowner uses the correct terminology for dwell, %, not degrees, I've said degrees from the year dot, no idea why !

50% is the way to go for a points gap of .015."

I've had old Fords that have the points at .025", dwell for them around 40% I seem to remember.

A bit of discussion is good education, great forum this one.

Regards all, Terry
East Yorks.