Ignition Timing Confusion

G15 Roy · Post by **G15 Roy** » Mon Feb 25, 2008 11:02 am

Is it now running OK.

snatchpiece · Post by **snatchpiece** » Mon Feb 25, 2008 1:16 pm

quote:
Is it now running OK.

It appears to, although I've only done 12 miles on it, hopefully I'll soon get a chance to give it a prolonged run. However I seem to think there's a noise from the top end when hot..........or could it be me?

If the ignition timing is slightly out (remember I used a metal rod and not a drinking straw or tie wrap ) what are the tell tale signs?

GSAX1 · Post by **GSAX1** » Mon Feb 25, 2008 1:55 pm

Too much retarded ignition: Reduced power in higher rpm range, running hot, spitting in carburettor.

Too much advanced ignition: Harder starting, pinking when pulling hard and throttle is opened, somewhat reduced power in lower rpm range.

Michael

Circlip · Post by **Circlip** » Mon Feb 25, 2008 2:55 pm

Probably as much as 15 degrees in between those symptoms, maybe more.

Degrees advance is what means something, not inches of piston movement.

Somebody say crude? you can say that again.

Biscuit · Post by **Biscuit** » Mon Feb 25, 2008 5:10 pm

The 'rod down the hole' is inaccurate, due to the angle of the rod, which in effect is the hypotenuse (remember that!) of a triangle. The difference can be determined by looking at 'Tech. Articles'-'Electrical Technical'-'Ignition'- 'Trignition timing marks' by Norman Bird.

Another way of obtaining the timing, assuming you have the timing cover off, is using the teeth on the timing gears, any one will do. Each tooth represents 12 degrees, in your case full advance is 35 degrees BTDC, so from TDC you need to turn the engine back 2.9 teeth.

And before anyone tells me you can't use the cam gears because of the ratio, we are dealing with increments of movement, not revolutions per given unit of time.

Another fallacy is that you have to take the primary case off to use a timing disc. Drill and tap the half-time pinion bolt 2BA, or any suitable thread to your taste, and fix the timing disc there. A spacer will be needed to clear the pump housing.

Merlin · Post by **Merlin** » Mon Feb 25, 2008 8:57 pm

Alan a whole generation of bikers have timed their bikes using sticks or such down the the plug hole with good results why try and complicate a simple task?(chemists do it simply)

matman · Post by **matman** » Mon Feb 25, 2008 10:13 pm

My "rod" for ignition timing is a (bicycle) spoke, which nearly matches the spark plug hole vertically. There are three marks on it (TDC, 9mm BTDC, 11mm BTDC), which I have checked at least a dozen times - by repeatedly turning the engine to and fro - to assure they are "correct".

For my 650 twin I choose the 9mm (~ 11/32") mark which should correspond with about 35 degrees advanced spark - the manual advance/retard will do the rest.

"Pushing" the lever will slacken the cable and give fully advanced ignition, pulling it will give retarded ignition - so you normally will have to ride with completely pushed lever.
Remember that the choke works just the other way round! - push lever to start, pull it to ride!!

Biscuit · Post by **Biscuit** » Mon Feb 25, 2008 10:33 pm

Come on Stinky, whats complicated about counting teeth passing a fixed spot?. You don't get inaccuracies by having to make two marks and judging them against a nebulous point on the head.

Generations of, (did you say BIKERS?), motorcyclists have poked sticks down plug 'oles because they don't think.

matman · Post by **matman** » Mon Feb 25, 2008 10:45 pm

quote: Generations of, (did you say BIKERS?), motorcyclists have poked sticks down plug 'oles because they don't think.

Me, I´m just too lazy to take off the timing cover and adapt a timing disc...

Biscuit · Post by **Biscuit** » Mon Feb 25, 2008 10:58 pm

Agreed if you are just checking, but if you need to adjust - off comes the timing cover.