My 400 set up for mx is just about were I want it. I could maybe withstand a few more little mods and I was thinking about having a angle job done and putting in some after market valves and springs and etc.

I'm a little hesitant about 5 because I have been told that only select mechanics can pull this off successfully and I'm afraid that if I send it out now, that I will miss most of the season.

Any info from you boys would be very appreciative and good luck everyone...

 

I wouldn't worry about a 5 angle valve job. I've not heard of this as being a common mod, and it would take a very gifted worker to do it properly. IMO it would be a waste of time and money for no measurable gain. When you get your top end freshened in the winter just have them do the head maintenance at the same time and you'll have a good reliable machine. Keep in mind that oversize valves usually go along with an increase in engine displacement through a big bore or stroker or both type of mod. If you increase valve size a lot on a relatively stock motor you risk losing low end power for a small gain in top end, which is not what you will likely want for MXing.