Honda 400EX, what mods to wake up bottom end?

JM PRO

JM PRO

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Hi everyone,

I went online and there are thousands of responses for my question but thought I would ask our sand community since the bike will only be ridden in Glamis. Bike is in great shape just looking to increase power and bottom end torque. I would rather not spend too much money, let's say a budget of $500. Let me know what your thoughts are and if you have any suggestions where to buy to save a buck. Or if you're selling any parts for cheap hit me up.

Thanks in advance!

Matthew

 
Sorry, but you're trying to hot rod a tractor.....Use them for what they are... reliable as a rock. If you feel the need for speed...get a 450.... Shock work would be better money spent. 

 
Respectfully disagree.

We put a 440 jug and 12.5:1 piston and an FCR carb in my son’s 2004.

Made a pretty noticeable difference. Different power and than a 450s for sure but keeps up with them all day.  Walks away from stock 400’s.

 
We ran one for many years and my wife loved it. Actually preferred it over the 450. Exhaust, jetting, aftermarket filter and box, hotcams stage I cam and +1 or 2 teeth on the rear sprocket (I can’t remember). It ran great. Quite a bit stronger than the stock bikes and didn’t have a problem hanging with the 450s. I used to love riding that thing around in the dunes!

 
i have a 440 big bore kit piston sleeve gaskets and rings for 110 dollars if interested call me gary 909 214 8930 in the ie but work all over

 
450Rudy said:
Respectfully disagree.

We put a 440 jug and 12.5:1 piston and an FCR carb in my son’s 2004.

Made a pretty noticeable difference. Different power and than a 450s for sure but keeps up with them all day.  Walks away from stock 400’s.
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If you are going to mod it,... this^^^. But as RBL said, a 450r is a better starting point, and rides better .

 
I've done this to my own TRX400EX and it hauls my fat ass everywhere in Glamis

Curtis Sparks Timing Key - $15 (Only use on stock motors) - snappier throttle response, increased hp. It will run a tad hotter, watch temps.

Front Sprocket $15-20 - Go down 1 tooth for more bottom end grunt, it will be a wheelie torque machine, slight loss of top-end speed...but these are not super fast anyways.

(good time to look at rear sprocket and chain, depends how they look if you change all at same time)

Open Air Box - K&N Filter w/ Outwears Cover, proper carb jetting.  Costs here will vary, parts are cheap, labor is free if you can do it yourself.

White Bro's E-Series slip on exhaust is what I have and its perfect...but they don't make them anymore. Find a slip on that fits the budget..don't waste big $$, just need something USF Legal and opens up enough for some gains.

:ftf:

 
many have already chimed in but my short list would be.

Open the air box

Front sprocket - 1 tooth or rear sprocket + 2 teeth. depending on availability ( my understanding is a 1 tooth adjustment on the front is = to 3 in the rear)  

Header and Exhaust.

Updated CDI

After the airbox and exhaust you will want to rejet the carb. The manufacture of the exhaust usually will let you know what you'll need. 

Anything more were opening up the motor.

cam , Valves , Port and Polish, larger jug, lighter crank..... 

 
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My only issue with the 400 with my kids, was they just don't have the top speed to keep up on some of our dune rides.  Sure gear it up helps, but then that takes away some of the torque.  My son floated a valve, which then bent the crank..........$3500 later to fix it.  4 strokes in my opinion are ticking timebombs once you start going into the engine; pipe, rejetting, and airbox is as far as I go anymore, not worth a full engine rebuild down the road.

 
Cookie said:
My only issue with the 400 with my kids, was they just don't have the top speed to keep up on some of our dune rides.  Sure gear it up helps, but then that takes away some of the torque.  My son floated a valve, which then bent the crank..........$3500 later to fix it.  4 strokes in my opinion are ticking timebombs once you start going into the engine; pipe, rejetting, and airbox is as far as I go anymore, not worth a full engine rebuild down the road.
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This, Ran lots of 450's in our group and we ran the crap out of them. Never did we open up a one for more than a HRC cam upgrade. Never did we have one come apart either.  Well not one that didn't say Suzuki on the side...

400, just dial in the suspension so they can stay on the gas longer, it is the only real way to make them faster and remain reliable.

 
I love my 400EX. Did the typical mid pipe and muffler from FMF, opened up the air box, and put some air scoops up front to help cool it. Dont know if those help, but they look cool. Used to take me everywhere in the dunes, and I was never slower than anyone unless we were going up Olds or something. Enough fun for me, thats for sure. Currently need a carb rebuild (or maybe a whole new carb?) to get her running again. They are so fun!

 
What year did the headlights on the 400EX get upgraded, they look really nice.

HD-wallpaper-quad-bike-red-sand-blond-bike.jpg


 
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