I have put in a white bros box temporarilly and tested it on some hills and trails. I can say that it did not make any difference at all. We had two stock bikes with K&N, and WB E-series. They were both jetted the same. One was a little faster than the other. We took the box out of the faster bike and put it in to mine and there was no change at all. Anyway I am looking for midrange HP. At the Dunes you do not spend very much time in 5th gear wide open. I am looking for HP in 3 and 4th 3/4 and up throttle.

 

416EX...to answer your question from before:
I am running the "stock" 12-discs in my E-Series, and aside from whats listed in my signature below, I have a 6" (yes, 6-inch) port in the top of my airbox, with a directional, screened vent covering it. This gives me the airflow of not running a lid, but when I go thru water, none gets in my airbox.

Also, my cam is ALL ABOUT midrange...and the addition of the 416 bore with higher compression meant I lost no low-end power, gained quite a bit of mid, and gained some top. With my mods, the quad pulls good start to finish. A rev box really does nothing for me, because I make all my big power in the mid...adding the 16T keeps me from hitting the rev limit too quickly, makes me faster in each gear, and faster on top speed.

ccole99:
You can do all the engine mods you want to a 400EX, but they will NOT increase your TOP SPEED. You will GET to your top speed a lot quicker than other 400EX's, but top speed remains the same. The only way to increase the top speed of a quad is to mess with the gearing (front sproket, rear sproket or tires). My 416EX with 16T sproket keeps me right with a 250R's top speed (in 6th)...not sure how many MPH that is...I assume around 68-70MPH.

 

Thanks MIA great info. Do you have any personal experience with the HRC Cam?

 

Would someone please explain how when my friend with a stock 400ex races a guy with a 416 11:1 compression,GT thunder porting, UNI filter,wb rev box,22inch tires and HRC cam gets beat by the guy on the stock bike. They have raced many times and the stocker still takes it. The 416 does have a better power band and feels stronger but just isnt as fast in a drag. Why is this?

 

That should never happen, a built bike like that should smoke a stock bike. It is probably a problem with jetting. I know my bike kills stock 400's and I have basically the same mods.

IS HE RUNNING ANY AFTERMARKET EXHAUST SYSTEM.

 

Adding mods CAN increase top speed, say if you don't have enough power to get the motor to rev out in high gear? Wouldn't adding mods give it power to pull the highest gear more easily. RdingManiac420...Don't forget that I got my 180lbs fat @ss compared to Jordans 130 lbs. Also, Now that I put my 20inch tires (sur-traks are a bit heavy) and went back to my 15 tooth, I've been taking him in drags. I'm not running an AF pipe...I did derestrict my stock one, but I never had money to spend on it...probably because I used to spend so much on weed. Now that I quit I'm gonna have a full DMC by x-mas:-) Also, all of our drags have been on dirt roads and in the woods, and with my bald tires and higher HP, I seemed to do more spinning than moving foreward.

PS. I don't have a WB rev box, it's an XR250 box

 

MIA so what your saying is a stock 400 and a 400 with a slip doesn't make enough power to hit top speed of the stock gearing? This is why i ask. The Raptor has been clocked at 70plus mph while the 400 has been clocked at mid 60mph(Dirt Wheels)with my slip on i could not run with the Raptor on top end at all he would pull away(he was picking up speed i was not) but now with my mods he can get a ahead by about a half quad then we stay the same for has long has we race on the flats. So if he is going 70mph what am i doing if i am beside him? I hope this don't sound like i am a smartass not what i am trying to do. Is there a way you can figure out top speed by the gearing ratio? Thanks for your time.

 

RdingManiac420-
most likely his gearing (22" tires) may be causing him to be slower off the line, or he isn't as good of a rider as the other guy on the stock bike, or there is something wrong with his 416 (jetting or worse)...entirely possible.

ccole99-
Most stock 400EX's barely have enough umph left in 5th to hit the rev limiter (and thus top speed). Even with a slip and jetting, some 400EX's may not hit the rev limit. I cannot explain why you are able to hang with a Raptor at top speed--stock 400's should not be able to do this, unless the guy riding the Raptor isn't hitting 5th gear (duh), or has screwed something up with his motor or gearing. With all of my mods, I can hang with a Raptor and 250R all the way thru the gears, and up to top speed. This is due to my 416 generating more power throughout the gears and gearing that gives me the higher top speed. I do not have a rev kit because my quad is all about MID-RANGE power, that, and I do not want to stress the hell out of the internals of my 400. If someone came out with a +500 RPM rev kit, I'd buy it...but all the ones out there are 1200+ RPM, and thats too much for the 400 to handle long term.

250rampage-
I stand corrected: The only way engine mods will give you a LITTLE more top speed is if you have a rev kit, and your quad still generates power topped out in 5th--stock 400EX's and a lot of modded ones DO NOT generate power past the stock RPM limit. But again, generally, gearing changes will net more substantial top speed increses (or decreases).

TOP SPEED does not = TOP END POWER/PULL/ACCELERATION

 

I have a friend that has a dyno and I am going over there this afternoon for a test and tune. I still have not added the cam but I will report as best as I can what I find. I have just the 11:1 pistion and other mods as I have described. E me with any questions you have I will get back to you Friday with the dyno results.

 

I'm not stock i have 416, Hrc cam,WB slip on,K&N jet filter kit with Gt Thunder porting.