I bought a White Brothers rev box brand new and I put it in my 400EX today. It caused my engine to overheat, I was running really lean,and I think I blew the rings or messed up the valves because it won't start. Has anyone had the same problem? What should I do about it? Should I have rejetted the carburetor after putting n the rev box? What can I do to make the rev box work with the 400EX?

 

my buddy has a mod rev box and he has had no problems with it.

if u hooked it up wrong it woundn't limit the revs and you might of over reved it and blown it up.

 

No I am positive that it was hooked up right, but maybe I got a rev box for the wrong model. I don't think that I did but it is slightly shorter than the stock. I think that the extra revs just sped up the inevitable. I think that I blew the rings or a valve or two which were probably going to go pretty soon. I did not notice anything wrong with the engine before the rev box was put in though because I could keep up pretty good with my buddy's piped 400EX.

 

MY WBBox also had "WB" scratched into the case and it is smaller. I have never had a problem with mine. The only problem that I did have was not being able to start in cold weather; had to put in the stocker.

 

Hey honda400rider, thanks man. I was worried that it wasn't a White Brother's rev box and that I was sold an inferior one instead, which blew up my 400EX. I now realize that, more than likely, it wasn't the rev box that caused the EX to die out. It was probably the low oil level that caused the engine to overheat because I was going up a long hill and the oil pump probably wasn't getting enough oil to the engine. I bought it on ebay brand new for under $65 and was worried that the buyer had screwed me over but I am sure now that he didn't. Thanks again for your help.

 

400EX's heat up really fast...make sure you have heavy oil..filled up...maybe even look into air scoops and a bigger oil cooler. I use 15W40 and 20W50 synthetic oil (synthetic oil doesn't break down as fast as regular oil)..I also have air scoops..