Microlighters

Hi guys hoping to put my ducati ignition 503SC back together soon.

Just been having a look at the CPS DVD for putting these engines back together and the guy re-building the engine says the timing is set to .069ins BTDC.

But on reading my rotax manual it gives a fig of .059ins BTDC or 1.47mm.

My dial gauge is metric, so can any of you guys confirm is it .069ins or .059ins.

Nick.

Nick, I don't have any access to any 2 stroke tech docs but my little conversion program says 1.47mm = 0.05787 inches. Seems 0.059 is the right one. Typo from CPS?

Hi according to CPS they seem to say due to the angle of the plug hole the .069ins fig is a compensated fig.

But as I say the rotax manual gives .059ins.

very confusing I am not sure now what to set it to.

Nick.

If in doubt...............do what the book says.

I am now totally confused, I set the timing on my ducati ignition 503sc with the dial gauge to 1.75mm or 0.069" as per the CPS book and advise from others, the idea being as the plug hole are angled on the 503 you need to compensate with the dial gauge hence 1.75mm.

And just to double check I put a protractor on the flywheel zeroed it at TDC, turned the engine back 16deg as per the rotax manual to find that the timing is a mile out when set to the above.

Now the rotax manual gives the timing as 16deg or 0.059" or 1.43mm all BTDC, and with the timing set at 16deg BTDC the dial gauge reads exactly 1.43mm or 0.059 BTDC as per the rotax manual.

3 different people have told me to use the compensated figs of 0.069", but as I say they dont and up when you double check with a protractor

So were do I go from here I dont know which figs to use.

Nick.

Nick.....do exactly as the Rotax manual says and you'll be ok

Hi Duck that's the prob the manual just give you the figs ie, 1.47mm or 16 deg BTDC.

Other books I have and internet sites give a compensated setting fig due to the inclined plug holes were your dial gauge would fit, using this method seems to put the timing out by around 2 deg at 18deg BTDC,

As it stands at the moment I have used my dial gauge to find TDC and with a protractor on the flywheel turned back the flywheel 16deg,

I think I just need reassurance that the way I have done it is ok.

Nick in the UK.

Sorry to have kept you waiting for the reply, but I had been working the entire weekend.
You did it exactly right........by the book :D
I have always done it that way and have never had a problem. To hell with the "compensation" theory

ps. I bet you've done it already and it works :D

Thanks Duck that settles it then.

Nick.