Timing - how far past TDC?

[nic-clark]

Hi,

I wonder if anyone can help me here... I have the marine version of this engine with a magneto, but leaving the mag aside (there is a good spark at 4 plugs) I am trying to get the timing right to start it. At the moment I have set the spark to occur at TDC, but all I get is the occasional misfire and smoke from the carb.

I think that perhaps the spark is coming too early - before the valve is open so the fuel is possibly ignited second time around? Should I advance the timing a bit by rotating the engine past TDC? Any help appreciated!

The magneto delivers a spark at the plug wires well and the spark is good. It mates with the engine timing chain by using a pin in a drilled disc. Basically, I hold the mag at the point just before it is going to fire a spark to #1, move the engine into position and then slot the mag into the disc so the pin goes into one of the holes, bolt it up quick and try to start. So it's not as easy as coil and battery timing to play with!


Thanks,
Nic

[les]

The spark usually occurs a little before TDC, not past it.

[nic-clark]

Thanks -that could be why then. Not my strong point, timing. I will check again!

[simmitc]

Also be sure that your have the plug leads in the correct order and that you are timing against the correct cylinder.

[nic-clark]

Thanks, all in correct order. As on my other thread I am having trouble verifying that the mark on the engine crank start wheel (where the fan would be) is indeed TDC.

[nic-clark]

Hi, sorry to keep asking questions about this obscure engine, but I really do appreciate your help!

I have adjusted the timing, and the engine nearly started - on the starter it was keen to run and went by itself a few seconds. I think I still have the timing too far advanced- you can see the mark for TDC on the wheel, and the timing marks I have tried so far. I used the leftmost one most recently. Pic here: https://goo.gl/photos/ASh6b6CZNdtM21kU9

I think I need to move it back towards TDC?

I have the firing order correct, and I am timing on #1 cylinder, the one that is the opposite end to the gearbox.

Any ideas would be really helpful.

Thanks, Nic

[nic-clark]

Rob - thanks for your PM but I can't PM back as it says disabled?

Mine is not an impulse magneto it mates to the engine using a vernier disc with a pin in. It is an RF-4. It has a manual retard lever.

I was just trying to contact you after your post about Mike's vedette.

You were talking out about setting timing at 24 degrees - is that before TDC or does it need to be on the magneto. At the moment there are 4 good sparks at the plugs.

I would really like to get it going so any help appreciated!

The mag is in good condition so I would rather not replace it. The engine ran well last year before I needed to take thhe magneto off to do some other work. The previous owner also replaced the internal coil with an external one, but I have put an original back inside. I have an electric starter!

Thanks!