I am thinking of installing a White Bros. rev limiter. My bike is running stock exhaust and air filter. Will I need to change the jetting? Has any one installed one of these on a stock 400 without adding the pipe and filter? Did it make a difference? Thanks

 

The WB rev limiter, Ithink is just from a xr400 dirt bike. There are some places that you can buy the box for a lot less cost. The box will make the 400 very hard to start in cold weather. The box is made for a kick start bike and you electric starter will not spin the engine over that much in cold weather. There are some boxes out that will let the 400 start good in cold weather. Mine has been removed for the winter.

 

How much power did you gain? The weather here is about the same all year 40-65 degrees. We do have some cold day's but I don't ride it too much in the winter. Did it make a noticable difference?

 

From what I understand, the box will let you rev 1000 rpm more. The bike has already achieved its maximum hp by this time, and is on the downcurve. Motors are made to quit revving at a given point for a reason, to keep you from sitting on a grenade. I'd spend the $100 elsewhere.

 

Quadfather is right.

The box will not add any HP. It will let you rev the motor out a thousand more RPM's.
Will not make the bike faster in any way.

IN FACT, if you take advantage of that new limiter and rev the bike out to 10,500 RPM, and if I was racing you (when my bike was stock) and I were to shift slightly below the stock limiter, I would win the race. You will be slowed down by shifting at 10,500. The 400EX likes to be short shifted and its torque taken advantage of.

-Matt

 

DON'T BUY THAT STUPID BOX. YOU DON'T GET ANY MORE POWER. YOU ENGINE WILL SOUND LIKES ITS BLOWING UP IF YOU TRY TO REVV IT HIGHER THAN STOCK. MY WOULD NOT LET ME START MY QUAD IF IT WAS COLD OR IF THE BATTRY IS LOW IT WOULD START. I WAS RIDING DOWN RAIL ROAD TRACKS AT 9:00 PM AT NIGHT BY MYSELF AND GAVE OUT LEAVING ME PUSHING HOME. IF YOU WANT ONE I WILL GLADLY SELL MINE FOR DIRT CHEAP.

 

A month or two ago in one of the ATV Mags there was artical on 400EX Mods and the talked the rev box down. You didn't get much power gain for the money and extra stress on the motor will make it less reliable. I think that I'd spend the money on a cam, a Pipe, or some sort of suspention update.