Why is this happening?

[kraqus]

I recently and finally upgraded my RN with the usual "Head and Pipe" combo. This is a Girdled ADA head with 35cc domes and after one ride I noticed one O ring popping out of the dome next to the spark plug.....Bad O ring? Defective dome?

It is a used head I purchased and it was in great condition or at least I did not noticed anything wrong with it.

Benny

 

[Big Kahuna]

I would say it was the wrong sized oring.
Never seen that before.

 

[SUPERTUNE]

If you did use the right o-rings (v020) (v024) (v043) you could be having detonation or domes and/or head shell worn out, Never use a used a ADA head unless it has been measured for wear.