Ignition timing

[florence]

I have noticed that some people mention dynamic timing.

I have always static timed mine and it seems to run fine.  Does dynamic timing actually make a difference?

What is dwell? Does this only apply in the USA?

[Seamus]

Hi Florence

Dynamic timing is using a strobe. Theoretically better because you are checking the timing when the engine is running. This should be more accurate and you can see if the advance is working.

Dwell is the number of degrees on the cam that the points are closed. The closed position allows the coil to obtain the correct 'charge' (for want of a better word), so that when the points open, a good spark is generated. Too short and the spark will be weak. This is usually sorted by adjusting the points gap.

Hope this makes sense

Seamus

[florence]

Thanks Seamus, I think I'll leave alone because it seems to work well.

[Bryanj]

Seamus is not quite right for the Honda's as on full advance there is not exact timing mark just two lines that the timing must be between, Honda consider it more important to have the timing correct at tickover.

Dwell is an electronic measurement of points gap and as different people "Feel" the drag on feeler gauges differently more accurate than using feelers----especially when its a Numpty apprentice doing the job------20 odd(make that 30) years ago i had an argument with an apprentice about doing points and timing on a ford V6 with him saying it couldn't be do accurately without dwell meter and strobe, so i showed him on mine and when he played with his electronic bits it was spot on and he wandered off mumbling rude words

[SteveD CB500K0]

I have a strobe and have tried it many times over the last 30 years. I never really got on with it as
a) it jumped around abominably and was very difficult to read
b) it never showed that my static setting was wrong

Now I don't bother and just use the static method

[Spitfire]

I've always used static timing to set up bikes, but when I restored my F1 I did try out a strobe with very little sucess so I have gone back to the old tried and tested method.

Cheers

Den

[Seamus]

Not to get into an argument,  but all I said was that the engine was timed running and not static. I thought better of going into advance at higher revs as it was not really appropriate to the question. Just a simple explanation of the terms.

You can check the advance with a strobe, but only if it is working and at what revs it happens (if you use an accurate rev counter). The only way that you can time at full advance in reality is if you mark up the plates with a timing disc etc. to give a reference point.

Anyway, these old motors seem to be pretty tolerant with respect to timing being spot on, otherwise they would not have survived the 70's (or the folk that worked on them) 

Cheers

Seamus

[Bryanj]

Using a strobe at tickover is not a good idea as the advance weights start to move almost as soon as the engine is running, they may not be supposed to but they do---especially with 30 year old springs

[florence]

Thanks for your contributions, to conclude it seems we think static timing is a good method.

For some reason I cannot ever get the timing correct with the recommended points gap of 14 thou because the points never close at that setting.  I have to set the gap really small to allow them to close as the points cam doesn't seem to have much lift.  Is this normal?  Also with a larger gap there isn't enough adjustment in the second set (i.e 2,3 ) to allow them to be timed.  Is it possible that my points cam is worn out or maybe that the pattern points are not quite to the same spec as the original fittings?  I've never known points cams to wear out before but then I suppose anything is possible.  Your thoughts and experience would be very much appreciated as I have never come accross this on any other vehicle before and I do work on a lot of engines.

[totty]

I've just gapped mine to the lower end of the book setting which from memory was 0.3mm, the gap was adequate but I only just got the second set timed as it was right on the limit of adjustment. I'm new to these bikes but I have seen a worn points cam on a Ford (cracked cap possibly allowed something abrasive in) so it's worth checking

[Bryanj]

If you cant set at 14 thou with the cam at highest lift and the points still close at lowest there is something major wrong somewhere.

NOTE:-

you set the gap with the points open the most NOT at any particular mark

[florence]

Maybe something is wrong then, It's never been able to have correct points gap and that is with the points cam at highest point.  Looking at it carefully it is almost impossible to distinguish the highest point, it seems almost round, maybe it's very worn, it came out of the bikes original engine which was pretty much worn out but I have worked on some pretty tired machines for years and never known a points cam to wear out. I put oil on the felt thing periodically.  Thinking about it logically there must be less than 14thou of lift on the cam otherwise it would work, unless I am missing something.

Hopefully, Dave Silver will have one and I hope not too expensive.  I don't really want to go over to electronic ignition because it's too costly and prone to going wrong.

[Bryanj]

It is difficult to judge the highest point when you dont do it very often, i also have never seen a cam worn out and unfortunately it only comes with the complete advance unit, best money ever is the complete points plate from Mr Silver instead of just points, if it it "Loose" int the 3 mountings get some old feelrs or better shim stock from an engineering supplier andform som L shaped pieces to go from the mounting screw behind the plate around the outer edge to take up any gap, difficult to describe but dead easy to do

[Yoshi823]

I had a problem on one of my 550s once. I couldn't see what the problem was but it just wouldn't fire up after I had got to my destination & finished doing business. I checked the points gaps etc but it just would not go. Luckily I was within a stones throw of a Honda dealer (Greyhounds in Croydon), so I bought a set of OEM points, installed them & hey presto, first push of the button. When I got home I compared the heel of the pattern points that had been in the bike previously with the new ones...the OEM ones appear to have a Tufnel heel, the pattern items have a plastic heel, & wear quicker. A lesson learnt.