503 Pre Igniting

[REDROMAN]

When switching of my engine it still turnes for some time and then enentually goes dead.This happens even after short idleing.The engine has 124 hours on.I removed the exh manifold on Saterday and was suprised to see how beautiful the pistons looked.No sighns of carbon - except one can not see that well on top of the pistons.The engine was decoced on 97 hours.What can the reasons be and what else could cause this problem.

[Duck Rogers]

The usual reasons are excessive carbon build up and/or a wiring fault.
Seems you got the carbon problem under control.
Look for a bad "earth" connection on your mag switch/switches

[Sad-Ham]

I had a similar problem on my 582 at around 230 hours, after switching off the mags it would splutter and poep for a whole while before it died. Took it to the guys at rotax who rebuilt the carbs... problem solved.

[Duck Rogers]

Took it to the guys at rotax who rebuilt the carbs... problem solved.

Huh?.....can the guys at Rotax, or anyone else for that matter,explain to me how rebuilding the carbs will cure a "running on" problem? I would like to learn something new.
Sad-Ham, it's not directed at you at all mate. I just think "they" happened to get lucky at some stage, either with the wiring or the carbon issue and found the problem was cured, and so labelled it "carb rebuild".
Just my opinion. But seriously, would like to know if a carb rebuild can cure a running-on problem?
Anyone?

[Sad-Ham]

I had checked all the wiring and put a can of PowerTune through the carbs to try and clear ant carbon before I took it to them, the soultion they gave sounded strange to me too but I was happy to be rid of the problem for a couple of hundred bucks!

[Tailspin]

Duckie

It is possible that the carbon that was causing the problem was cleared before the motor went for the rebuild.

From what Sad ham is saying i think that could be the most logical reason for solution

Just my 2K Zim$