1990 Ktm 500 - What is the correct Ignition time spec BTDC ?

[jurado]

I have just restored a 1990 ktm 500, two-stroke, and I am not sure about what ignition time spec should run with. I know the ignition time spec is very important for engine performance, and would like to ensure I am using the correct one. I low time spec would result is significant power output. I also know a high time spec would damage the engine (and your foot when kick-starting!).

I have a manual for a 1990 ktm 350 cc and it says ignition time spec should be 2.1 mm Before Top Dead Center (B.T.D.C.). I own some other 350 cc bikes (360 h7 Montesas, with similar 350 cc engines and compression ratios), and they properly run with 3.0 mm BTDC time spec. So I do not understand why the ktm 350 time spec is lower.

Assuming the 2.1 mm spec is correct for the ktm 350, should not the ktm 500 run with a bigger spec, let´s say 2.5 mm, or 3.0 mm ?. A bigger spec would seem logical to me, since there is more volume of compressed mixture to ignite since sparks till piston reaches its TDC

Your views appreciated.

Regards,,,,, Jurado.

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http://i56.tinypic.com/125i0xu.jpg

[jurado]

now with picture.

[LWC82PE]

You can find a workshop manual here

http://www.repairmanual.com/category/ktm-atvs-and-motorcycles/
should have timing spec in there

[jurado]

Thanks. Indeed, the manual talks about an spec of 2.1-2.2 mm BTDC for the 500 cc engine. However the manual also says that this spec is for the MOTOPLAT ignition system, but for a  SEM K11 ignition system should be 1.45-1.55 mm BTDC, which does not make sense to me.

I have read that the correct spec for the 500 cc engine is 2.5-2.9 mm BTDC. I would expect that when increasing the spec you loos some power at low rpm, but gain at medium-high regime. Tou might get some kickbacks if spec is too high. I wonder whether someone has experience in all this.

Thanks,,, Jurado.