Need Help...pleaz

[JAE400ex]

I have a 01 400ex, completly stock, bought it brand new,i mostly play ride on dirt roads and will go to a near by sx track, i am looking for some cheap horsepower tho, i have about 800-900 dollars to blow, i plan to buy a k&n air filter, do i need to jet my carb? if so, is tat very difficult, I am hoping to mod my bike up enough to race (and completly SCHOOL)my buddie's 02 Yamaha wz400f dirtbike,
i would like a slip-on that would add significant power and torque in the high rpm range and sounds pretty throaty (about like if you take the spark arrrestor off,by the way, does taking this off add any hp?) if any body has any prices, hp numbers on the yamaha and wat i would need to add, it would be greatly appreciated.

[zrpilot]

The best bang for the buck mods on the 400EX are:
1) no air box lid
2) K&N or UNI filter
3) HMF Slip-on muffler
4) Re-jet to match intake and exhaust mods.

This will cost about $300-$400 depending on where you buy and how much of the work you chose to yourself (it is NOT hard!)

It will gain 3-5HP.



I doubt you will be able to spank a 400cc dirt bike because of power to weight ratio, all things being equal.

Just my $.02

PS: for more power a high compression piston and cam can be added for another $400-$450 and will make the power gains even more, still doubt it would embarrass a 400cc dirt bike though.

[firefighterjosh]

I suggest for starters get this

#1 HMF Slip on $400......Full system you gain more power but is more expensive not sure on the price

#2 I would go with a foam filter. And if you ride in mud leave the airbox lid on.

http://www.rockymountainatv.com/productDetail.do?prodFamilyId=2687&navTitle=Filters&webCatId=27&pageLinkUri=&vehicleType=&webTypeId=4&navType=type

#3 Rejet your bike


I would the save some more money and upgrade your suspension.

You can get something like this
http://www.rockymountainatv.com/productDetail.do?prodFamilyId=8841&navTitle=Suspension&webCatId=13&pageLinkUri=&vehicleType=&webTypeId=129&navType=type
For around $400 and should work fine. Then you can send you rear shock out for around $200 or so dollars and get it revavled.

[JAE400ex]

yes i have seen the yammer hammer run, and run it does, it is VERYY light and after idiling for about 5 min. the first 7 inches of the header was glowing red on a 20-25 degree day,if i had the money i would definatly buy one, even tho its a aginst my Honda-sim religin hahaha

[JAE400ex]

yes i have seen the yammer hammer run, and run it does, it is VERYY light and after idiling for about 5 min. the first 7 inches of the header was glowing red on a 20-25 degree day,if i had the money i would definatly buy one, even tho its a aginst my Honda-sim religin hahaha

[400exrider707]

Originally posted by firefighterjosh
I suggest for starters get this

#1 HMF Slip on $400......Full system you gain more power but is more expensive not sure on the price

#2 I would go with a foam filter. And if you ride in mud leave the airbox lid on.

http://www.rockymountainatv.com/productDetail.do?prodFamilyId=2687&navTitle=Filters&webCatId=27&pageLinkUri=&vehicleType=&webTypeId=4&navType=type

#3 Rejet your bike


I would the save some more money and upgrade your suspension.

You can get something like this
http://www.rockymountainatv.com/productDetail.do?prodFamilyId=8841&navTitle=Suspension&webCatId=13&pageLinkUri=&vehicleType=&webTypeId=129&navType=type
For around $400 and should work fine. Then you can send you rear shock out for around $200 or so dollars and get it revavled.


$400 for an HMF slip on? Let me know where you buy parts so I can stay away from there.


Do pipe, filter, lid, rejet, piston and cam, and pick up a shop manual for your quad.

After all this, your friend on the bike is still going to school you... unless he really sucks at riding.

[miller821]

A 14 tooth sprocket will give you good torque for the trails... 15 bucks to.

I recommend my mods (below)

Not necessarily the FMF, but any pipe is better than stock.

[hornetgod13]

All the recommended mods will help your 400EX run stronger, faster, and smoother but, you'll never hang with or "school" any 400CC dirt bike. Quads are so much heavier and are geared differently. Your only hope is if he's a crappy rider.

[northwest Texas]

You can forget about schooling your buddy on his bike........it ain't gonna happen.

Get yourself a Uni air filter and a slip on exhaust (your choice).

Then get yourself some front shocks. You don't need all the adjustments and/or reservoirs unless you really know what you're doing.

That will take up most of your money.

Better shocks will make you able to ride your quad faster.