I know with most engines when you start changing stuff in the top end like cams or start playing with compression, you will get more valve train noise than before. Does this hold true with the 400ex as well? When I did the cam and 11:1 piston I noticed the chatter but figured I'd let it go until I put an hour or two on it and readjusted the valves according to the break in schedule. The bike doesn't smoke and I'm positive it isn't the piston making the noise. So I just got done readjusting the valves and changing the oil/filter again, and the chatter is still present. On the other hand, the bike runs awesome, so this is purely a "in the long run" type of question.

 

I always adjust RFVC engines one feeler tighter than what the book calls for, there is alot of junk rolling around in these enginges with the sub rocker arms. if it sounds like a power stroke diesel, they are just too loose

 

I agree tighten them up a bit. If your performance goes down put them back where they were and deal with the noise. It should fix it though.

 

so if it's not something that's detrimental to the motor I'll just run it for a ride or two, go one thousandth tighter on the valves, and if it's still noisy I'll just use thicker oil. Thanks for the responses. Now I just need to get the jetting right, I've got 5 brand new 215 main jets from a different project, hopefully one of those will do the trick.

 

Its the cam. I had a Hotcams Stage 1 in my 400ex and it sounded like a typewriter.

 

haha, yeah a typewriter is a good analogy. I think it's fine, it hasn't gotten any worse and I ran the heck out of it in the snow today. Maybe I'll pull the oil filter and check to make sure there's no metal, and then I'll just get used to it. I think the only time the noise is going to be a "problem" is when I sell the bike and someone tries to tell me I should take money off because the motor taps, lol.