Rejet or no???

I've got a 78 KZ650 all stock except Mac 2 into 1 exhaust.
It is running very rich and plugs don't last long. This
I am going to pull the carbs clean and rebuild them and
put on a new Vance and Hines 4 into 1 exhaust. Hoe do I
find out which jets to use. And would a rich mixture cause
the plugs to die after only a couple of hundred kliks.

Thanks
Bob:blink:

Cow_Man wrote:

I am going to pull the carbs clean and rebuild them and
put on a new Vance and Hines 4 into 1 exhaust. Hoe do I
find out which jets to use.

By riding it, see how it runs, see what jets are in it now, and adjust from there.

Cow_Man wrote:

And would a rich mixture cause
the plugs to die after only a couple of hundred kliks.

Thanks
Bob:blink:

The plugs should not die. Carbon might need to be cleaned off, but if the plugs are seriously fouling that is usually caused by oil.

The bike does not use any oil or blow any blue. The plugs
do not look overly fouled just a fine black soot. I could
not get the thing to even fire, I put new plugs in and it
took off and ran smooth as silk first kick. I have just
in a new Dyna S ignition system and there is plenty of
spark. I did notice one of the old plugs had a weak spark
from the centre electode to the theaded part of the outer
plug not the bottom tang like it should.

Thanks
Bob

that mac pipe you have installed is not a real good performance pipe it's actally one of the few pipes that you would have to lean out your jetting after installing it.go down a couple of sizes and move the clips on your needles acouple of postions and try that to start and see if it is better. with the vance pipe you will have to go the other way.try going up acouple of sizes and ricen up the needle postion by two the other way. the vance would definitly work better with pod k&n filters they are more money but they work the best.