Ignition timing advice

If its too far forward , it gets all crankey . !

Id used 30 . Exact. on points . No More .

With the 70s / early 80s gas , most machines in top , and maybe third ,
would get slight pinging around 1/4 throttle under light load . flat Spot .
Chopping a gear or a few revs'd help .
On the Commando it was a Stutter at 3.200 .

being primative three stage carbs .

The Commando , I think , is pretty resistant to pinking .
But putting lower or low octane gas in it , youll see if it gets all awkward and obnoxious ,
where you are with the Ign. timing setting . say 91, 95 , & 98 . If it were just shiity on the first ,

The 98'd be fine with that setting . If it were awkward on 95 too , youd wanna think some more .
the slide Cuttaways at about this setting ( the pinking spot ) so thyve some relevance there .

Top end rpm detonation is To High a C;R for that advance . Thats the disadvantage of high Comp Ratio .
It narrows the acceptable satisfactory ignition setting range .

a less obstroperous C R you can get higher advance , for better ' full burn 'of the charge .

The amount of advance - the olde BSA A65 Lucas A Adv. unit ran 50 % more than the Commando,
so at the same setting fully advanced , it pulled back way more at / for idle and gettaway .

Got away at 800 rpm from a 500 rpm Idel . ( acording to the crumy green spot tach ) on Mk II Amals .

THEREFORE THERES A FEW THINGS WOTS INTERRELATED ! .

It will never beat a simple positive stop.
I like to complicate some things (You're welcome Ludwig) and not try and reinvent the wheel on others.

The exception to this might be Kawasaki 750 triples (H2) and before TDC measurement settings for ignition timing over degree's.

" I would be surprised if running nicely with 26° was actually that, more likely more in reality unless "

kNACTUALLY oops . Running In , say below 3 or 4 grand , you may not know / notice it .

Hence

" Some unit single enthusiasts feel the 12 degree AAU is an improvement over the 15 degree AAU. This is specially true if you time 28 degrees full advance BTDC as suggested for the earlier Victors, as the 15 degree cam actually retards to 2 degrees past TDC. You may have to slow down the idle on the carb but it certainly won't harm and may even accelerate better. "

https://www.bsaunitsingles.com/item.wws?cpubcode=BSAU&sku=54427182 .

NOW , the various elec ign units have their own advance curve & quantity .

SO , with one , you could be at the same setting ( would ) at low rpm , but at the 26 instead of the 28 fully advanced . Id be cautious of 31 degrees . THREE EIGTHS INCH B. T. D. C . ( like a bonneville ) is the goal .
Which I believe is 30 . Where they all had a fit and said TWENTY EIGHT . UId think that over 9 1/2 C:R ( for the road ) youd wanna be very carefull . Need to start studying combustion chamber irregularities effect ,
then.
need to be optimum to get safe full ignition advance .

Going from avgas 100 octane to 98 pump gas it the T 100 r triton , with " Class C " sub 7.5 C R ( measured 7 1/4 ) running the 3/8 " B T D C setting , strting and running was impeeded .

The World Tour types ran Low C.R. so watered down donkey piss fuel wouldnt dissole their pistons . Theirs little point running over 8 3/4 c R for a everyday road bike , as things get more crucial .

Matt Spencer said:

I would be surprised if running nicely with 26° was actually that, more likely more in reality unless

Click to expand...

Yes.

My point was even though there was no point was, you can chase fairies (with 1° here, one any other way be it here or there) but to do so you need a verified method to read those degree's be it static or a full advanced strobed reading.
To do so is a time consuming exercise.

"a less obstroperous C R"

Holy Moly...had to go to the dictionary for that one!

Noisily unruly or defiant: The restaurant owner ejected the obstreperous customer.

(Probably tried to park his Norton out front instead of in the rear.

MexicoMike said:

"a less obstroperous C R"

Holy Moly...had to go to the dictionary for that one!

Noisily unruly or defiant: The restaurant owner ejected the obstreperous customer.

(Probably tried to park his Norton out front instead of in the rear.

Click to expand...

Some of us have University degrees, (Not me)
some of us are qualified in other areas,
Some of us , just get by . . . .

Bernhard said:

Some of us have University degrees, (Not me)
some of us are qualified in other areas,
Some of us , just get by . . . .

Click to expand...

Don't be obstreperous, Bernhard.

;-)

gortnipper said:

Don't be obstreperous, Bernhard.

;-)

Click to expand...

If you dont learn anything technical here, at least you are improving your vocabulary.

Bernhard said:

Some of us have University degrees, (Not me)
some of us are qualified in other areas,
Some of us , just get by . . . .

Click to expand...

I quit school to join the army so my vocabulary never really developed...OTOH, I did learn a lot of words in the army that I regularly holler when working on the Norton!

Bernhard said:

Some of us have University degrees, (Not me)
some of us are qualified in other areas,
Some of us , just get by . . . .

Click to expand...

I find that borrowing the ideas of people who really know what they are doing works for me.

With the proviso that you need to carefully read and understand why they chose a particular option to check it is relevant to your circumstance.

For example I mention Gordon Jennings before. He was the editor of Cycle Magazine back in the day and also a very successful two stroke tuner. If you race air-cooled two strokes then you really need to know ignition timing.

Somewhere I read an article about him preparing a Yamaha for Daytona. And in practice going quicker than the factory bikes.

In fact Kel Carruthers came over to check things out. Now if Kel Carruthers comes and looks over a guys shoulder then he is definitely worth listening too.

“I have never let schooling interfere with my education.”

a good deal of common sense is worth more than all the wonders of technology .
There was a good deal written on Commados , whilst they were current .
Theres been ' improvements ' since . But most ' faults ' are caused by human error , lack of maintance , negligence or incompetence .

seeing the entire exhaust white inside , and the plugs , at high speed cruise . I think 30 is far enough . Plug Center Posts ' rounding ' the corners prematurely ,
i.e. , in one or two hundered miles , ROUNDING them not just microscopic at the edges - Would indicate backing of the advan is required .Or the plugs are to hot .

N3s in the 7 1/4 : 1 Comp T100R , on avgas , at 3/8 " btdc ; N3s overheated in 1 1/2 laps on the Pukekohe Club ' short circuit ' . W F O predominantly . 8000 rpm tops .

Hard riding / High Comp ratio , one would do well to consider a cooler plug . Think it was the champion 57's or 59's cured it .
N3s trundling round in winter in the Bonneville - magneto . Would foul / blacken . unless one stood on it occasionally .

No doubt the wonders of modern tecnology have produced superior spark plugs now , compared to the 70's . ?

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