Best Bang for the Buck: 400ex

[KingpinsEx]

I have an '02 400ex with a totally stock motor and im looking for some more power. It still runs fine and isnt really needing a rebuild but im getting pretty bored with the power..I have considered buying a WR400 engine or 426 to put in, but rebuilding it would be cheaper right now im just wondering if it would be worth it in the long run.

Here is what i was thinking...boring it out to a 416, throwing in a higher comp. piston, stage one cam, HMF slip-on and possibly some porting. I plan to do all the work myself aside from the boring, im just wondering if this is a wise way to invest it. Anyone have a similar setup that can give me some feedback?

I'm wondering if i would be better off just saving up and building a hybrid instead. Or would this setup give me enough power to keep me interested, reliability is an issue of course thats why i want to go with the smaller overbore. I need to do something because with the prices of used atvs today its not worth getting rid of, so any input is appreciated!

I would get the yz400/426 motor in it. Its better than the wr. If you need lights it costs $170 to hook em up using the yz motor.

If you sell your 400ex motor and every thing you dont need you will get about enough money to build your quad into a hybrid.
It took me about 8 months to get most my 400ex parts sold in order for me to build the hybrid.

A yz hybrid is faster than a piped yfz450. You will here alot of people saying im wrong and that a yfz is faster but its not true they just see the less cc's. If the yz426 was bumped to 450cc it only would gain 2hp.

A yz hybrid will walk circles around a fully modded 400ex.

To me it seems almost to fast cause when i got it all running i kept almost getting yanked off the bars cause i was used to the EX.

[4TraxRider]

I think you'll be happy with your set-up. When I used to race a 400ex, I had a 406 JE 10.8.1, web cam midrange cam, fmf ti 4 muffler with powerbomb header and mild porting. It was very competative with the C and B class quads about 5 years ago. Look into some suspension though before you dump a bunch of money into your motor. The right suspension set-up will make you go twice as fast as motor work.

[zrpilot]

Originally posted by KingpinsEx
I have an '02 400ex with a totally stock motor and im looking for some more power. It still runs fine and isnt really needing a rebuild but im getting pretty bored with the power..I have considered buying a WR400 engine or 426 to put in, but rebuilding it would be cheaper right now im just wondering if it would be worth it in the long run.

Here is what i was thinking...boring it out to a 416, throwing in a higher comp. piston, stage one cam, HMF slip-on and possibly some porting. I plan to do all the work myself aside from the boring, im just wondering if this is a wise way to invest it. Anyone have a similar setup that can give me some feedback?

I'm wondering if i would be better off just saving up and building a hybrid instead. Or would this setup give me enough power to keep me interested, reliability is an issue of course thats why i want to go with the smaller overbore. I need to do something because with the prices of used atvs today its not worth getting rid of, so any input is appreciated!

I would do a 416 bore with the following mods. This whole rebuild may be $800-1000 though, so the hybrid or another quad may be less expensive:

416 JE or Wiseco piston 10.5:1 minimum
Heavy duty head studs
Full HMF exhaust or Sparks exhaust
39MM FCR or '05/'06 450R carb
Stage 2 cam
Port and polish (done by pros!)
Open air box
Uni filter

Originally posted by zrpilot
I would do a 416 bore with the following mods. This whole rebuild may be $800-1000 though, so the hybrid or another quad may be less expensive:

416 JE or Wiseco piston 10.5:1 minimum
Heavy duty head studs
Full HMF exhaust or Sparks exhaust
39MM FCR or '05/'06 450R carb
Stage 2 cam
Port and polish (done by pros!)
Open air box
Uni filter

For that amount of $$$chaching$$$ you could buya yz/wr motor that stock would have almost 50hp and would be liquid cooled. I would do the hybrid it would save time and not cost much more than building the ex motor. B4 i built my ex into a hybrid i was going to build my ex in to a 500cc beast but for the price of that i just went and built a hybrid. Worth every penny but still runs hot as the ex motor if not hotter.