more power?

[400exracer511]

I race a 400ex and everyone else is getting faster 450's but i like my quad and im goin to keep it so what can i do to get more power without spending alot of money or losing reliability... my motor is stock but i have k&n filter, jet kit and exhaust. I was thinking a cam and a CDI box..... am I on the right track? And with a 416 or 425 kit would i lose reliability? any suggestions will help alot Thanks!

[Toadz400]

I would go with the 416 kit, higher compression piston, CDI, bigger carb, port and polish, better cam and you wouldn't lose any reliability.

With the 416 you are still able to rev pretty quick but it also gives the 450's a run for their money, but once the 450's are modded out you have no chance...sorry to say, but the 400ex engine is definately outdated compared to the new 450's.

But what makes a HUGE difference is how your quad handles, upgrading your suspension and width of your quad will help you a lot. It's mainly the rider that makes the difference.

[400exracer511]

"I would go with the 416 kit, higher compression piston, CDI, bigger carb, port and polish, better cam and you wouldn't lose any reliability."

about how much would all of that cost me??

[Florida400EX]

Originally posted by 400exracer511
"I would go with the 416 kit, higher compression piston, CDI, bigger carb, port and polish, better cam and you wouldn't lose any reliability."

about how much would all of that cost me??

ALOT!!! Just start out with a 416, and a cam of some kind... Should run you around $250 give or take, and you'll notice a realy great gan! If that doesn't get your power where you wanted, then go into a new carb and porting.

[cals400ex]

i would do the cam and piston too. you will notice a very nice gain here. i noticed next to nothing with a carb, but i don't have a port job either.

[khen]

Originally posted by cals400ex
i would do the cam and piston too. you will notice a very nice gain here. i noticed next to nothing with a carb, but i don't have a port job either. I'm also looking at these mods.. What about a high compression piston/cam with the stock bore? Is there a big difference in power between a 416 high compression piston and a stock high compression? My EX is fairly new and I would rather not bore it if the difference is small.

[atcyalater]

Originally posted by khen
I'm also looking at these mods.. What about a high compression piston/cam with the stock bore? Is there a big difference in power between a 416 high compression piston and a stock high compression? My EX is fairly new and I would rather not bore it if the difference is small.

Someone can correct me if I'm wrong but I don't beleive you need to bore for a 416 sleeve it will fit in the stock bore. I have done a lot of research on this lately because I have been considering putting a 416 kit in my 400EX. I wanted to do a 440 kit but you need to bore the case to except the 440 sleeve so I have decided to do the 416.

[Florida400EX]

For the 406, 416, and 426 you will still be able to use your stock sleeve. For a 440, you will need a new sleeve (most 440 kits come with them), and have you cylinder bored and the sleeve installed. It's much more reliable to stay on the stock bore. The most common size that people choose is the 416, because it has a great gain in power, and you still have another overbore on the stock sleeve left.

[cals400ex]

yes, you use the stock sleeve for everything up to a 426. well, i guess you can replace the sleeve but there is no real reason too. i am building a 426 and i went ahead and replaced the sleeve for a little extra strength.

however, you still need to bore out the sleeve to fit the larger 406, 416, etc pistons in the stock sleeve.

i can't tell you how a stock bore would compare to a 416. i honestly don't think there would be a large difference. i did run a 406 and i can tell you in a drag race a piped and jetted z400 never beat me. at the time i was running sparks x-6, stage 2 hotcam, 10.8:1 ross 406, rev box, and jetted stock carb.

[khen]

Good info! Thanks for all of your help..

Do I need to go with hardened valves and rockers and/or heavy duty springs with a stage 2 hotcam or could I get away with the stock ones?

[Florida400EX]

You can get away with stock rockers and springs for both hotcams.... I'd recommend the WB track cam... or GT thunder, both are the same exact cams....Hotcams are cheaper, and more convenient though.

[cals400ex]

you need to use stock rockers with the hotcams!!
stock springs is what most prefer too. i think you can use aftermarket ones but you won't want too stiff with a drop in cam.

most web cams use hardened rockers. you can call the manufacturer to confirm this. also, i think gt thunders cam now use stock rockers but i am not 100% sure. that is something you can contact gt thunder about.

yes, the hotcams are convenient and i have had great success with them. nice power gains too. the stage 1 seems to be pretty "ticky" but the stage 2 didn't seem to have that problem.