Ignition timing in degrees

[muskrat]

G'day Fellas.
I'll throw my two bob's worth in.
As Rob say's about higher compression the flame is faster so less advance is needed (31-32 BTDC). Then if using higher octane fuel the flame is slower so more advance is needed (34-35 BTDC).
It's all a bit "suck & see" as each motor/owner is different (combinations of above and riding style). I just keep advancing the timing till it pings then back it off a degree or two.
Cheers

[limeyrob]

I was chatting to a guy with a race stock car - a Ford Galaxy. I asked him about timing: He said the only way to tune it was advance until it pinked then back off a gnats.  That gave a timing of 45 deg advanced! He said that was because the combustion chamber was such an awful shape, it wasn't a hemi, and the plugs were right over one side.

[Rex]

Add in the fact that it's very old machinery (Galaxy or A10) that has suffered God-knows-what mods from standard over the years, and that method is the best way rather than trusting to arbitrary figures (possibly) set decades ago.

[RichardL]

Orabanda’s Dynamometer testing is more recent than decades ago.

Richard L.

[Rex]

Of course, but how many engines would he have tested to reach those figures? As previously said, all engines differ, so try and tune to the individual engine.

[orabanda]

Seven A10's were run on the dyno.
Also Yamaha two and four strokes; slight retardation (around 2 degrees) was the optimum setting for engine performance.

Cheers,
Richard

[Sakura]

Well, there's no point in asking a question and then ignoring the answers. If I say so myself, I'm an extremely experienced fitter/mechanic but not an experienced tuner. I generally just follow the manual. I'm going to start with 33 degrees. It's manual adv/ret so I can monitor pinking easily. Thanks for all the input but don't stop if you've got something extra to add.

[berger]

why not just do what i did with my manual mag on a bit of a hot shooter, set it at 3/8ths full advance 36 degrees and there is plenty of retard to stop mine pinking if i force it labouring in gear, in fact there is enough to blue the exhausts.

[sean]

berger
same with my super rocket 3/8th ... which is basically the same as the RGS motor starts first kick 9 times out of 10 with a slight retard on the manual lever and crap 10% ethanol gas

[Adler]

Hello Sakura,
searching the forum for certain topics, you always find hundreds of other highly interesting topics ... a time consuming habit and highly interesting ... 
Now, I found this thread - Sakura, I hope my post is still interesting for you as I thought, maybe graphically checking the difference of a one mm longer carillo conrod compared to the standard A10 one in terms of the BTDC discussion. Do the same, what the crank, the conrod and the gudgeon pin do. Have a look yourself at the attached pdf.
black = carillo rod at 8,73mm (11/32) BTDC => 33,8°
green = std A10 rod at 8,73mm (11/32) BTDC => 33,7°
Just for comparison the 5/16 value
magenta = std A10 rod at 7,938mm (5/16) BTDC => 32,1°
I had the same problem during my A10 restoration and found this procedure in a book and it helped me to find the degree value I wanted to know. In general, with this procedure you can convert a given BTDC value for any engine setup from mm to degrees and vice versa. All you need are basic things from school (ruler, protractor, pair of compasses (?), pen), but it is recommendable to use the doubled scale to get it more accurate. Have fun.

In the end, I just managed to find the value roughly and with Mr. Orabandas slotted mag flange tip I managed to get it right, means, I am happy with a first or second kick starter, cold or warm and I have no need for the 100% best performance out of the engine, although thinking about the masterpiece investigation from Orabanda "dynoing a dynosaur" and his other posts to this subject ... hm ... maybe ...

Best regards, Manfred

[Colsbeeza]

Hi Sakura,
 I downloaded Beezageek's ( he has changed his handle since - he might comment later )spreadsheet a few years ago and made modifications which I now cannot remember why ( must be alzheimers ).
I found it to be good for any motorcycle.
Col

[Sakura]

Thanks all for your contributions.  I set it at 33 degrees which seems to be the general consensus. Haven't had at chance to try it yet - too many other distractions.

[Topdad]

I think Orabandas mag flange idea is the dogs wot nots , so needs considering given what you are doing best of luck Bob