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Re: BSA M20 running HOT, HOT, HOT

ps The mag cable has an adjuster a few inches from the adv/retard lever on the handlebars.

Also, download the Workshop Manual in the Technical Section.

email (option): sacombsashtrees@hotmail.com

Re: BSA M20 running HOT, HOT, HOT

Thanks Patrick!

email (option): carlrholm@gmail.com

Re: BSA M20 running HOT, HOT, HOT

If I understand the user's manual correctly, the lever pushed away from the rider is retarded ignition, pulled towards the rider, the ignition is advanced.

However, I can't seem to pull it more than about half to thirds of the way back (to the position which I think is full advance). Also, when at idle and I push it away, it seems to idle much more smoothly and at lower revs. But it was with the lever pushed away that I rode the last three miles, and as I said, she was smoking (probably from burnt oil inside the motor) by the time I got home. I'm confused!

email (option): carlrholm@gmail.com

Re: BSA M20 running HOT, HOT, HOT

I'd stop riding it until you have worked out how the advance/retard is set up and operates...You risk doing serious damage if you ride the bike fully retarded for any distance...

Look on the technical section of this site where there is a full explanation of the principles of advance and retard and how to identify which set up you have...It's all in a lengthy article on ignition timing...

The limit of movement of the adv/rtd lever is determined by a slot ground into the contact breaker cam and a pin fixed into the magneto body...The cam moves to advance or retard the timing when you pull/push the lever.
The pin, which sits in the slot mentioned previously, limits the movement of the cam itself...

So, don't expect to see full movement of the lever when you are pulling it....

I'd advise you to read the article in the technical section to provide some clarity...Ian

email (option): ian@wright52.plus.com

Re: BSA M20 running HOT, HOT, HOT

Hello Carl,

If you your engine revs slower when the lever is pushed away,
It sounds like you have the correct magneto, and slacking the cable retards it.

Pulling the lever for about third of the travel is OK. It does not travel too much.

On the other hand, if you rode the bike as you describe, it was fully retarded, and probably- therefore heated so much.
The ignition has to be set with the lever fully pulled, and then the points are just in the absolutely about to be opened position,
(And the points gap is set correctly)
And the piston st 7/16” / 11mm BTDS on the compression stroke. (See tech section)

You can have indication if you have any advance at all, by pulling the lever and try to start a bit slowly.
If you have some kick back from the kick started, then you have SOME advance. You cannot tell how much,
But at least the ignition is not retarded.

The bike does usually sounds better idle retarded or less advanced, but you would feel a significantly more pull
If you try to accelerate for few seconds with retarded ignition, and then advance.

There is no problem, of course, to start the bike retarded and then advance, if it is easier.

Good luck,
Noam.

email (option): noam10@gmail.com

Re: BSA M20 running HOT, HOT, HOT

Ian and I wrote together,

So you better listen to him...

email (option): noam10@gmail.com

Re: BSA M20 running HOT, HOT, HOT

..I think you know what you're talking about Noam..Ian ...

email (option): ian@wright52.plus.com

Re: BSA M20 running HOT, HOT, HOT

Hi Carl

Two types of mag fit an M20.

You can distinguish which one you have by looking at where the advance/retard cable enters the mag at the contact breaker points.

Looking at the bike from the nearside (left hand side of the bike), below the dynamo sits the mag. If the adv/ret cable enters the mag at around 10-11 0'clock i.e. on the left hand side of the mag at the contact breakers, then you have a slack wire advance.

This means that to advance the ignition, you push the adv/ret lever away from the handlebars and to retard the ignition you pull the lever towards the handlebars.

This set up is NOT standard and is the reverse of what it says in the manual. This type of mag is a post war mag and my understanding is that these mags were fitted so that if the cable broke (doubt it ever did) the cable would be slack and therefore the ignition advanced so that there was no danger of running the bike retarded.

If the above is not the case then you probably have the proper wartime mag i.e. to advance the ignition you pull the adv/ret lever towards the handlebars and to retard the ignition you push the lever away from the handlebars; a tight wire advance.

The other ways of knowing which type of mag you have is by kick starting the bike.

Pull the adv/ret lever towards the handlebars and kick the bike over. If it kicks back, the ignition will be advanced. If it starts OK without it kicking back, then give the bike a few minutes to warm up a bit and settle down. The engine should now idle on its own. If you push the adv/ret lever away from the handlebars and the idle speed increases, then you have a slack wire advance i.e. a non-standard post war mag.

If what I have said in the above paragraph is the reverse of this, then you probably have the correct wartime mag i.e. a tight wire advance where lever positions are in accordance with the manual.

Whether you have a slack wire or tight wire mag, always check the timing fully advanced.

Regards

Pat

ps Be careful kicking off a bike with advanced ignition. It is best done with the bike on its centre stand and you not sitting on it.

email (option): sacombsashtrees@hotmail.com

Re: BSA M20 running HOT, HOT, HOT



..I think you know what you're talking about Noam..Ian ...


Thanks Ian.
Coming from you it's a huge compliment...

Cheers,
Noam.

email (option): noam10@gmail.com

Re: BSA M20 running HOT, HOT, HOT

I add 1 liter of diesel to every tank I re-fuel. Helps to keep the temp. down.

Re: BSA M20 running HOT, HOT, HOT

Hi Michael.

I do not add anything but some lead substitute additive when I remember to,
And ride the M20 in heat of 30 Deg' centigrade, and in the city with no issues,
But if adding anything,
Wouldn't it be better to add a bit of a good synthetic 2T oil, say 1% or less,
Instead of Diesel?

This oil was made and engineered to lubricate barrels under working conditions
And high revs of 2T motors...

BR,
Noam.

email (option): noam10@gmail.com

Re: BSA M20 running HOT, HOT, HOT

well i'm afraid it will carbonize and build up on the internals as combustion and compression on these ladies are very low. i would avoid oil.

Re: BSA M20 running HOT, HOT, HOT

Hi Michael,

The new synthetic 2T oils are designed to minimise carbon deposits and hardly smoke,
With very good properties of friction reduction under hard conditions.
I use full synthetic "Rapsol" oil for my 2T vespa, and it hardly smokes, if at all,
And after many miles (And even more Kilometers )
The combustion chamber and piston head are almost totally clean.

I am not arguing, of course, as I am not an oil expert.
Just a thought...

Cheers,
Noam.

email (option): noam10@gmail.com

Re: BSA M20 running HOT, HOT, HOT

you are right, of course, regarding those benefits of the new 2 stroke olis available today, but i use diesel in order to reduce the octane, making the engine to run cooler, not for oiling propuse

Re: BSA M20 running HOT, HOT, HOT

Forgive my ignorance but I had always thought octane rating had no effect on engine temp as long as the petrol was sufficient. There's a formula online as to how much paraffin one can add and still be ok but I would have thought diesel might add a bit of lubrication as well. I know modern fuel burns hotter. I've got a colder plug than normal in my 16H to stop it pinking up [very] long hills

email (option): j@clogmaker.co.uk

Re: BSA M20 running HOT, HOT, HOT

Hello
First i would check oil is returning into the oil tank. Take the oil cap off when its running there should be oil flowing out of the pipe. My advance lever moves about a third, the speed should increase as you advance it.Take the points cover off kick the bike and note the direction then move your advance lever you will see the cam ring moving too and fro.When the ring turns in the same direction as the points turn that is retarding, when they move in the opposite direction that is advancing the timing.
Good luck.

Haddy

email (option): mhadfield35@yahoo.com.au

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