Author Topic: Advance/Retard  (Read 357 times)

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Offline Vitesse

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Advance/Retard
« on: 14 May 2020 at 09:04 »
Okay, no tut, tutting in the cheap seats . . . I've recently bought a Mk4 and as this is the first bike I've had with a manual advance/ retard I'd appreciate a little advice on its use.

I do understand varying ignition timing to cater for variations in engine load and speed so that the "best" performance can be obtained but I am unsure when one uses the advance/retard lever in practice? I am guessing fully retarded (cable tight) to start but when does one advance it? And... do you "play" with it while driving or do you stick to fully advanced once the engine is warm?

Handbooks of the day do talk about altering the timing before tackling hills, and the like.  Is that a thing and how much?

Thanks.

Offline EW-Ron

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Re: Advance/Retard
« Reply #1 on: 14 May 2020 at 09:47 »
Well I can't speak to a Mk 4, but the bikes I've had with manual advance needed about half retard to start,
and then you advance it fully on the move and leave it there.

If you are required to halt with prolonged idling then there may be some advantage to retarding it a bit,
supposedly from a wear on the big ends point of view, but you have to be sure to advance it when on the move again.
I've not seen any advantage in retarding it for hills or similar. For really slow riding there may be some advantage.
If fully retarded it may conk out though ?

I'll be curious what actual Mk 4 owners will add to this.
Cheers.


Offline yosemite

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Re: Advance/Retard
« Reply #2 on: 14 May 2020 at 13:58 »
Okay, no tut, tutting in the cheap seats . . . I've recently bought a Mk4 and as this is the first bike I've had with a manual advance/ retard I'd appreciate a little advice on its use.

I do understand varying ignition timing to cater for variations in engine load and speed so that the "best" performance can be obtained but I am unsure when one uses the advance/retard lever in practice? I am guessing fully retarded (cable tight) to start but when does one advance it? And... do you "play" with it while driving or do you stick to fully advanced once the engine is warm?

Handbooks of the day do talk about altering the timing before tackling hills, and the like.  Is that a thing and how much?

Thanks.
sorry but no the ignition timing on your mk4  should be fully advanced with the cable tight, most bikes have ignition retarded with cable tight
as for riding I normally just leave it fully advanced once under way only retarding the ignition rarely.
Paul

Offline DJS

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Re: Advance/Retard
« Reply #3 on: 14 May 2020 at 14:30 »
I have a Mark 4 and the full advance position is exactly as Paul describes - lever pulled towards me so the cable is tight.

I start from cold with the lever in the mid position and once underway put it in full advance and leave it there.

Only if Iím going to be sitting stationary for a while do I go to full retard.

Hope this helps.

David

Offline Vitesse

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Re: Advance/Retard
« Reply #4 on: 14 May 2020 at 17:29 »
I have a Mark 4 and the full advance position is exactly as Paul describes - lever pulled towards me so the cable is tight.
I start from cold with the lever in the mid position and once underway put it in full advance and leave it there.
Only if Iím going to be sitting stationary for a while do I go to full retard.
Hope this helps.
David

Well thanks gentlemen - that certainly wasn't in the brief from the previous owner. I'm certain I've read you both right but to confirm: Cable slack is ignition retarded as used for starting and to reduce overheating if stationary. Cable tight is fully advanced for normal use.  Generally don't adjust it other than for starting?

Offline DJS

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Re: Advance/Retard
« Reply #5 on: 14 May 2020 at 21:05 »
I have a Mark 4 and the full advance position is exactly as Paul describes - lever pulled towards me so the cable is tight.
I start from cold with the lever in the mid position and once underway put it in full advance and leave it there.
Only if Iím going to be sitting stationary for a while do I go to full retard.
Hope this helps.
David

Well thanks gentlemen - that certainly wasn't in the brief from the previous owner. I'm certain I've read you both right but to confirm: Cable slack is ignition retarded as used for starting and to reduce overheating if stationary. Cable tight is fully advanced for normal use.  Generally don't adjust it other than for starting?

Thatís right except I set to half advance for starting - not fully retarded.

Offline cardan

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Re: Advance/Retard
« Reply #6 on: 14 May 2020 at 23:31 »
Most road bikes have "slack wire retard" - if the cable breaks you can start the thing and get it home. Most racing bikes have "slack wire advance" - you can keep racing at full advance if the cable breaks.

Here's a perfect example from Bob Cordon Champ's Sunbeam book. In 1930 Sunbeams used square ML magnetos, anti-cw rotation for the drive end. On the road-going Models 8 and 9, the a/r cable is at the rear of the magneto, giving slack wire retard, while the racers Model 80 and 90 have the a/r cable at the front, giving slack wire advance.

I don't think I've ever seen a "slack wire advance" Lucas magdyno, but if there was such a thing you might find it on a road-going 90 Plus. Because the bikes we play with are so old, you need to check what is currently fitted to your bike.

Cheers

Leon

Offline Vitesse

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Re: Advance/Retard
« Reply #7 on: 17 May 2020 at 19:38 »
Well - just had my first ever ride on the thing. Utterly alien to anything I've ever ridden before.  So many questions.

But sticking to the subject. Riding around the Adv/ret seemed to make little difference.  Stationary tickover was slower when retarded. Would I be right in guessing that modern fuels (even with ethanol) are so much higher quality (certainly higher octane) than what was available in 1950 that the adjustment isn't as critical as it would have been?

Offline EW-Ron

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Re: Advance/Retard
« Reply #8 on: 17 May 2020 at 21:37 »
Congratulations on your first foray back into history  !

Would I be right in guessing that modern fuels (even with ethanol) are so much higher quality (certainly higher octane) than what was available in 1950 that the adjustment isn't as critical as it would have been?

Thats entirely a correct assumption - and one that you don't often see in writing.
Having fuel that doesn't pink or knock at every slightest provocation would be every riders dream back then, I'd think.
And the reason that compression ratios were kept (very) well below double digits for many a decade...

Offline Vitesse

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Re: Advance/Retard
« Reply #9 on: 17 May 2020 at 22:05 »
Congratulations on your first foray back into history  !


Wait till you see my other post!

Offline EW-Ron

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Re: Advance/Retard
« Reply #10 on: 18 May 2020 at 01:39 »
Preparation is everything !
As someone said, you need to view that manual to sort out a few "teething troubles".

I put some tape on the tank with 'brake' and an arrow on the appropriate side,
and more tape on the other side with 'up for slower' on the gear side.
It saved quite a bit of stomping on the gear lever (goes faster !) rather than hitting the brakes.
Folks say they can adjust and do it perfectly all the time, but I found if you swap systems a lot,
having that tape and arrows saved a few faux pas when you least needed them.
Just practice (a lot) before doing it in the dark !! (!)