Adding power!!

[ohsobad_chevy]

I have a 04' 400 EX and I have already put a HMF full system exaust, rejetted the carb (of course) and put a UNI air filter on it. I am interested in adding some more power though. I am more interested in low to mid end power, for example, I want to be in second gear and when i hit the gas, the front end will try to raise up. Can someone tell me the best modification to the 400 ex that will add the most power and throttle response. :D

Thanks,

[corm]

416 kit give u alot of low end torque.

[ohsobad_chevy]

I dont want to go that far, yet. I am curious what the hot cams will do for my quad. As far as if they are worth spending $150 on.

[sixer3]

gearing....

"gearing is a horsepower"- grandpa keeps tellin me that =/

[PismoLocal]

get a 14 front sprocket and a 39 rear and your 400ex will be a wheelie machine.

[wolffie]

try getting a high performance piston! it doesnt neccesarilly have to be higher compression, but that should help. I think the cam will be more noticable in the mid range, but it should help the low end a bit. as mentioned before, you could gear it down a bit, but you are probably better either getting a cam, piston, or if you have the cash, a 416. also, dont forget about a rev limiter, just make sure it is a reliable one!

[ohsobad_chevy]

I have the general understanding of how the engine works and all, but is putting a new piston and cam in an engine easy or am i better off having a mechanic do it. If someone has some online articles on putting a new piston or a cam into a 400ex, that would be awesome.
By the way, Thanks for all input here. You all are a lot of help.

Thanks,

[Eddiesanders250]

Go with the cam for sure. It will make a big difference, never done it myself but i wouldnt touch that stuff. Of course im used to working on 2 strokes

dont be scared of opening the motor up. it is a cakewalk with a shop manual. I have a haynes manual.

my motor as it sits, not my first time, I'm 16.

dont let all the little parts scare ya. expecially the top end. as long as you lable the bolts as you take them out. mabie event punch the valve cover bolts throu a piece of card board in the shape of where you took them out.
you should do fine. really isnt that much at all. expecially scence it is air cooled, no anti freez to deal with.

[DAVE14]

gearing will help alot a 14 tooth front gear does wonders on an ex but a higher comp. piston will be pretty good too as for hotcams I run a stage 3 440 so my motor is mainly a top end machine but gearing will help you the most I wouldnt open it up for a cam without at least a std. bore high. comp piston to really feel the results or youll just get your hands dirty twice

[400exrider707]

Originally posted by DAVE14
I wouldnt open it up for a cam without at least a std. bore high. comp piston to really feel the results or youll just get your hands dirty twice

He hit the nail on the head here. Although if your really budget minded do the piston first, it will give a nice bottom end boost.

[bmurray]

I want to be in second gear and when i hit the gas, the front end will try to raise up.

I know on my stock 05 400ex, when I hit the gas in second my front end comes up. This thing is a torque monster!

Originally posted by bmurray
I know on my stock 05 400ex, when I hit the gas in second my front end comes up. This thing is a torque monster!

you obvioulsly havent ridden a 440.

lol, jk.




Please dont take that offendsively.

[ohsobad_chevy]

I have an 04' Ex man, The gearing is a little different on your 05', I do believe. I understand that I can get new sprokets and gain torque, like someone said above, but i want to keep the same sproket and just add more power. If that makes any sense. My quad will raise up the front end in second, as is, but i have to have the rpms higher. I am talkin about goin slow in second and poping the gas and having the front end come up.

416 bore is like 200$ with the work
another 100 for piston.
another 40 for misc
20 for shipping

if you put it on yourself it isnt that bad cost wise. and farily simple

[400exrules]

Originally posted by wolffie
try getting a high performance piston! it doesnt neccesarilly have to be higher compression, but that should help. I think the cam will be more noticable in the mid range, but it should help the low end a bit. as mentioned before, you could gear it down a bit, but you are probably better either getting a cam, piston, or if you have the cash, a 416. also, dont forget about a rev limiter, just make sure it is a reliable one!

wtf do u need a rev limiter for?!?!


just get a 416 with an 11:1 JE piston. a 416 only costs like $50 to get it bored, and you can use the stock rod with 11:1

[chevrolet486hp]

Do some light porting just clean up work on the INT & EXH. you will gain some nice tourqe all trew the RPM range the cam would help even more. porting is free.

[400exstud]

Originally posted by chevrolet486hp
Do some light porting just clean up work on the INT & EXH. you will gain some nice tourqe all trew the RPM range the cam would help even more. porting is free.

Cleaning rough surfaces is free. Good porting by experienced engine builders will cost you an arm and a leg.

[hrc]

How much worse will this stuff make your gas millage?

[buster369]

gas mileage on a 4wheeler? i dunno of anyone ever askin about that for a 4 wheeler

[ohsobad_chevy]

LMAO, gas mileage. Im sorry man, but if you are worried about mileage on a quad, your in the wrong game :D

[bwamos]

Originally posted by ohsobad_chevy
LMAO, gas mileage. Im sorry man, but if you are worried about mileage on a quad, your in the wrong game :D
Well if you race XC.. it is important to have a good blend of gas mileage and power. If you do a 5 lap race and your tank will only last 2.8 laps, you have to stop at the pits for fuel twice, wheras if it lasts 3 laps you only have to stop once. ;)

For the origional poster, a higer compression piston and a torque cam is a fairly low budget upgrade for some pretty decent gains. Wether you go 416 or stock bore. 416 is a good option though since it will barely cost you any more to do, and is still very reliable.