SOHC.co.uk Forums > CB350/400

It’s all about the timing

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Ken4004:

--- Quote from: exvalvesetdabbler on August 08, 2026, 09:12:50 PM ---It's the o rings between the inlet stubs and cylinder head that go rock hard.

Regards
Dave

--- End quote ---

Hi Dave , I did change the seals but will take another look at them , hopefully with the WD40 I should be able to isolate the leak so if I get time a job for tomorrow.

Thanks again regards Ken

Bryanj:
Its because of the "stutter" that its not worth checking timing mark with strobe at idle

Mikep328:
1. The erratic running you describe is not a timing issue. 
2.  Your timing light is functionally as good as one that clamps around the spark plug wire; it's just a bit less convenient to connect.  One could argue that it's MORE accurate since there is no delay while the sensor "figures" out there's a signal and sends a message for the light to flash.  Of course, since this all that occurs at the speed of light over maybe 1/2 metre, it doesn't matter!!!  :)

McCabe-Thiele (Ted):
I know the words "Dwell Angle" I have difficulty in understanding how it translates in terms of points gap & timing outcome.
In my head I've thought that whilst static timing is the basic set up to get the engine timing as close to correct as possible statically, the reality is that the timing might be slightly different when the engine is running.
This concept is why I've always seen dynamic timing as a a fine tune potential improvement with the added bonus as has been pointed out that you can also check the advancer is working.

I don't mean to Dwell on the issue (pun intended) but I've no understanding of what Dwell Angle really means in terms of spark delivery, I only know it matters.

K2-K6:

--- Quote from: McCabe-Thiele (Ted) on August 09, 2026, 11:13:14 AM ---I know the words "Dwell Angle" I have difficulty in understanding how it translates in terms of points gap & timing outcome.
In my head I've thought that whilst static timing is the basic set up to get the engine timing as close to correct as possible statically, the reality is that the timing might be slightly different when the engine is running.
This concept is why I've always seen dynamic timing as a a fine tune potential improvement with the added bonus as has been pointed out that you can also check the advancer is working.

I don't mean to Dwell on the issue (pun intended) but I've no understanding of what Dwell Angle really means in terms of spark delivery, I only know it matters.

--- End quote ---

To put it into more everyday terms, its the time that the coils are taking in energy  (with points closed) which of course gives ultimate output.

How it relates to crankshaft and hence "angle" is the degrees that the crankshaft moves while the points are closed, and ceasing at the point of opening.

To extend that, as the crankshaft rises in speed of rotation, then exactly the same angle gives shorter and shorter time in that corresponding angle (which doesn’t change) to give less and less "saturation" of coil energy as revs go up and up.

The coil resistance is set to accommodate both ends of this arrangement, much longer time at lowest rpm, to much shorter at redline. It can't effectively be avoided with singular point sets.

As the information posted above, electronic systems can provide fixed "dwell" by using internal switching that's timed in absolute terms rather than rely apon points opening and closing at variable rpm demand.

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