timing advance/retard lever

[jonathanjoy]

Hi ,
I’m setting the timing on my 1929 Scott. What do members recommend for the position of the advance/retard lever. Do I position mid way when setting ?

[dave bushell]

As an initial setting I always go for fully retarded at TDC. Otherwise 5/16″ btdc, fully advanced.

[jonathanjoy]

Hi
I’ve been setting mine at 2.4″ BTDC on the flywheel circumference, lever fully advanced. It starts ok, but as it picks up speed, do I need to advance it more ? if so the lever is already fully advanced !

[Barrie]

Timing should always be set at “fully Advanced “

[jonathanjoy]

I’m a bit confused, I static time it at 2.4 ” on the flywheel with the lever fully advanced !. The bike starts fine and runs at a slow speed, but surely as you increase the revs you need to increase the advance ? but if the lever is already advance I cant do this ! On later bikes this is done by a centrifugal weight on the points.

😕 😕 😕

[dave bushell]

5/16″ BTDC IS 2.7″ on the flywheel. Refer to chapter five of Scott Technicalities for a comprehensive guide to ignition timing.

[Barrie]

@jonathanjoy wrote:

I’m a bit confused, I static time it at 2.4 ” on the flywheel with the lever fully advanced !. The bike starts fine and runs at a slow speed, but surely as you increase the revs you need to increase the advance ? but if the lever is already advance I cant do this ! On later bikes this is done by a centrifugal weight on the points.

😕 😕 😕

This is because the full advance figure is the only known fixed point

[Kevin N Bayliss]

You time at max advance, as Dave said 2.7 inches btdc on the flywheel which is 68.5mm. (this is maximum unless you want to risk breaking the crank) Once the timing is set, You then close the advance lever and alter the advance and retard lever as and when required so the engine responds accordingly, you do not want the engine running at idle at full advance. This is a manual operation by the rider for different engine pulling conditions not automatic as per the weights which throw out and alter the points plate position.
I E when auto advance is used as the engine revs slow the ignition is retarded accordingly to the manufactures spec and as the engine increases revs then the ignition is advanced, unless you have a Scott with a distributor the rider has to alter the advance and retard according to engine speed and how the engine sounds. Kev

[jonathanjoy]

Thanks for the relpies,
Timed it at those settings, only seems to start at fully advanced !!! so I can’t advance it when it picks up speed. As I open the throttle the engine falters then picks up then falters again 😥 😥 but maybe it could be carburation. Its fitted with a Binks carb , I’m wondering if its worth investing in an Amal. HELP !

[chris wastell]

My ’38 model only starts at full advance. I run it like that all time only retarding it to stop the engine. Cleverer men than I have recommended on here before, running at fully advanced all the time. So maybe your Binks needs adjusting?

[richard norris]

If I were you I would try to borrow a carb which is known to work and try it on your bike thus working with a known quantity. Always worth yet another check to make sure that there are no air leaks. Good luck, you will get there in the end.

[jonathanjoy]

Thanks again , I think at the moment I’m trying all sorts in desperation. I need to be logical, its all to easy to start imaging all sorts of faults.
So I’ll make a fault finding flow chart. three main areas for investigation are:

Electrical
Spark , spark plugs, HT leads, graphite contacts , magneto HT . Low tension , gap , timing , short circuits.

Carburation,

fuel, fuel flow, float level, jets , slides

Mechanical

gas seal: transfer ports, barrel seal, glad seal, compression rings

I think that’s it !! just need to order them now !!! and research how to test each one

[Tman]

@chris wastell wrote:

My ’38 model only starts at full advance. I run it like that all time only retarding it to stop the engine. Cleverer men than I have recommended on here before, running at fully advanced all the time. So maybe your Binks needs adjusting?

If it were recommended to run always on full advance then wouldn’t Scott have fitted fixed timing ignition? You need to be able to retard it for starting and under load, like hill climbing.
If you retard it to stop the engine then the ignition timing “window” must be way out of sync with the movement of the cam ring.

My bike has a mark (on the handlebar lever) for full advance, and another for full retard, both marks taken from the movement of the cam ring, and it will run anywhere within these marks.

[richard norris]

Always worth checking the basics. BTW when was your mag last overhauled? Non-resistor plugs with the correct gap? Is there a fat blue spark? Does it still spark when retarded? I don’t believe exact timing is critical, 1/4 to 5/16 BTDC fully advanced should get it going.

[SwedScott]

Hi

As i fiddeled a bit with magnetoes I think that i can trow in a few bits. In some cases you overlook the most obvious, no offence I have been there several times myself!
The first thing is in wich direction is full advance? Is it with slack wire or with the lever pulled back? In many cases it’s with slack wire on BTH and with lever pulled back on Lucas. But if the magneto has been converted to run the opposite way around it could be the other way. And it can been “born” that way, too.
Look from the breaker side of the magneto. If the cam rings moves, when you pull the lever back, in the same direction as the breaker plate rotates. Then you’ll have full advance with slack wire, and opposite.

Regarding weaker sparks on retard: All manual magnetos are that way. The internal timing is at its best at full advance.
(But on the automatic advance magnetos the armature turn, so they’re always in the best spark position.) The most awkward work for a magneto is slow speed at full retard. If it don’t miss a spark there, it’s probably OK.

Best regards

Leif

[Author]

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