Timing problem resolved

[Anonymous]

I posted a while back about a bizzarre timing problem -- I was adjusting the timing on my '79 GS550L using a strobe, but was unable to line up the appropriate marks because the adjusment slots seemed "too short".

Anyway, someone at a scrap yard suggested to me last weekend that it might be a problem with the point gap. It seems that if the gap is made too large, this shows up as an advance in the timing. If the gap is made smaller, the timing is retarded.

I had set the gap to the high end of spec, because I thought it would be beneficial for the points to be as far as possible from each other when they weren't in contact.

To resolve the problem, I made the gap smaller, closer to the low end of spec. Without making any other changes, I was able to watch the timing fall back each time I adjusted the points closer.

I guess the lesson is, timing is affected by BOTH the gap and the position of the plates. Sound right?

Michael

[kz]

Re: Timing problem resolved

I guess the lesson is, timing is affected by BOTH the gap and the position of the plates. Sound right?

Michael

Sounds absolutely right too mee.

[saaz]

Absolutely right! The points gap directly affects the degree of advance. I found (after many years running points, including 3 in a GT750 waterbottle) that older points are best set by using a dwell meter, as the points gap is not an accurate indication of points dwell, which is what you are trying to set. By using a dwell meter and strobe light, you can set the points dwell/gap and timing with the bike running the whole time..and it is more accurate with older points.

[Anonymous]

I'm with Saaz on this one. Gap setting is crucial for the correct operation of the coil.

It surprises people to find that the plug fires when the points open, not when they close. They have to stay closed for a certain amount of time to allow a certain amount of capacitance charge to build up in the coil. When the points open this capacitance discharges rapidly and it is the rapid collapse of the magnetic field that generates the spark in the high tension lead of the coil, setting off the plug.

You need the points set so that they are closed for a certain amount of rotation, and open for the rest of it. This is what a gap setting meter tells you. When you set the points to a measurement like twenty thou or so, it is only the result of the company knowing what will give a close enough gap reading.

Kim

[kz]

I agree with both saaz and kkmiller and just want to add that you should always FIRST adjust the gap and check it with a dwell-meter.

After that is done you should adjust the timing.

If you make the adjustments in reverse order, you also readjust the timing then you adjust the gap and have to start all over with the timing adjustment again.

[Hotblack]

Wow I'm going to give mine another look. I knew to set the dwell before the timing, but I didn't reallise that setting it towards the high end would affect the timing THAT much. I set mine pretty much at the top of the range also, and sure enough the timing marks don't quite reach.

[Anonymous]

Dwell meter

Okay, the dwell meter thing is new to me. I assume I can get a dwell meter at most automotive stores... What exactly does the dwell meter do? How do I adjust the dwell with the bike running? What should it be set to? Thanks!

Michael

[Hotblack]

Dwell is just how long your points remain closed, which is affected by point gap. As long as your set your point gap properly, your dwell is OK, it's just two different ways of measuring the same thing. I could eat my words again but I don't think there's any advantage to using a dwell meter instead of feeler guages, except for convenience. On autos sometimes guages can be awkward, but on a bike it's pretty easy to wield them, I find.

[Dark Jedi]

Now you tell me!

Heh, spent all weekend fiddling with timing. I set it static, and I tried to set it running. All no good. I see a small blurb in the Haynes manual that reminds me of the dwell time's impact on timing, so I start fiddling with my gap. After closing the 1-4 gap a little, the bastard levels out and times perfectly.

But, I'd have never thought of timing or spark without pointers from all you good folks!