Hi all, could anyone help me understand why my plug is burning a certain pattern? It is whitish at the electrode base, dark at the electrode tip and mostly dark on the base ring. So it seems as if it is rich at some stages and lean at others, but I am at a loss to understand it.
This is for a Vortex Mini Rok 60cc engine running at a high speed, power track. The kart has good pace and RPMs but we seem to loose a little on top end relative to the rest of the field, especially later in the race. This should imply we are a little lean, but my understanding is that when the electrode tip is dark, the main jet is rich if anything.
Generally the electrode tip is used to gauge timing. I’m seeing detonation on that plug. If you look at the insulator you can see there’s small specs on it.
Thanks, yes I believe detonation may be a problem from running too lean. I will remove the head later in the week and take a look at the piston crown.
Interestingly, this engine’s timing is quite retarded relative to the factory spec, from testing at our local track. I must have just gone too lean on the fuel screw because my main jet and needle notch were not lean of the normal setting at the RAD for that day
I’m no expert by any means, but in my interactions with the Mini Rok those things like to be run lean as all hell. Looks like your main is probably too rich, but maybe a little lean on the bottom. White to no color seems to be pretty normal on those engines to get them to really perform.
Yes, our MyChron data shows the engine was revving extremely well - just over 15kRPM (96km.h) at the top end and 8300 (49km.h) at the bottom. But our lap times slowly dropped off towards the end of the heats, so I am pretty sure we were just a little lean.
Previously I have gotten great RPMs and good pace by jetting two jets lower, but after that race day I had to replace the ring because it was heat damaged.
When I started Mini Rok I was told you have run them lean, I think we have pushed the limits though.
