Plug chop, opinions please...

A good way to use an oxygen meter, might be to reverse calibrate it against your bike after you have got it performing extremely well right across all throttle openings, and never change the fuel composition. Sensibly for tuning, it should be measuring what oxygen is in the inlet charge, not what is in the exhaust gas.
Engineers have a habit of using scientists' black boxes - 'a little knowledge can be dangerous'.
I think Danno is right about the oxygen meter being intended to be used for environment protection purposes, rather than tuning.

Jim, what would you say regarding the plugs shown below sir?

They’re out of my 961, also plug chopped from WOT and the engine killed...

The lighting is not as good as the last pics, but from what I can see they look spot on.

Thanks Jim, that’s kinda what I thought.

I only know how to read a spark plug because I one attended a lecture by Barry Smith who used to ride for Derbi in GP. I think he became a 125 champion. It makes sense that colder plugs conduct less heat away than hot plugs. It is the porcelain insulator which conducts the heat away from the electrode, the black ring on the porcelain is the indicator as to whether the jetting is right. If you use a hot plug when you adjust the jetting, then fit the colder ones for racing, you will stay safe.

comnoz said:

The lighting is not as good as the last pics, but from what I can see they look spot on.

Click to expand...

I agree.

This is a very old thread. Sorry about bringing it alive again. I received a notification about the octane rating topic. I only use plug chops to check whether my main jets are still slightly too rich, and thast they actually come into operation at full throttle. It is possible to jet off the tip of the needles at full throttle when you use the leanest. That is not good. Damage only ever seems to occur when the motor is operating on wide open throttle. When I get to full throttle for any length of time, I use it as a slight reprieve for the motor. With methanol fuel, I run 670 Amal main jets - big enough for 12 to 1 compression. But it is very lean, right down the needles. When the motor is pulling, you get to high revs quicker if the needles are lean and you feed the throttle on, than if you run rich needles and whack the throttle open. The taper on the needles compensates for loss of vacuum. If you have bigger ports, you need quicker taper needles.