I just replaced the lower rocker box gaskets in my 98 1200S and noticed that there was only one umbrella valve in the head ,I only did the front one, I thought that there was two? if there is meant to be two why would anyone take one out? any ideas any thoughts would be appreciated, by the way ,any thoughts on synthetic oil causing leaks on older engines and no, I'm not trying to open a can of worms,see ya Lowie.