looking for some help from the 400ex veterans. trying to help out a friend. he wants to wake up his 400ex. try to keep up a little better with the 450's. any help would be appreciated. i'm thinking k&n, exhaust, maybe a good cam? let me know? thanks

what are the go to pipes for these quads with good low/mid power?

for years it seemed like the white brothers wb e series was the best for the money. it had different disks which changed the power ranges but i stopped seeing it a few years back so at this point i don't know but good luck hopefully someone else will help ya

i pipe and i big bore kit 416-440 kit is gunna wake it up a lot but start with pipe,filter,cam,big bore or porting or piston basically in that order

I have a white brothers e series on my current 400ex and had a HMF sport series on my last one. The HMF pipe makes more power, but it alot louder.

Had a wb e-series on my 02, k&n filter, and jet kit, seems like it made a difference, I was always behind on drags, but keeping up with them(450's) somewhat.

Sparks X-6

Hmf

Yoshi makes a good low to mid pipe for the 400ex check out rockey mountain atv they have about the best price, lots of used cams out there for sale, look for a TC racing cam or you could even get a Hot cam, if you want to run with the 450's you will need a plus 6 stroker crank a ported head and 12.5.1 piston with a FCR carb, I have a 460ex and it runs pretty good

i used to race the 400ex from 99-01... it was a great motor..

i ran a 416 11:1, with stg 2 hotcam, sparks exhaust, Xr 400 head gasket and FCR carb.

it screamed.

i had ran the White Bros, and Yosh exhaust before the sparks.... lets just say i would go with the sparks for sure!

LRD there pipes are great...i love mine

Sparks pipe for the 400 ex is the best bar none ! Cost some money but well worth it ..

Thanks guys i appreciate the info. sparks sounds good.
we're not looking to really drag agaist the 450s but he just wants to be able to climb the big hills at the dunes and stuff like that.
sparks pipe, k&n filter and maybe a hot cam stage 2. how much you think all that would cost?

I run the sparks for years. all out testing brought sparks out on top. Ebay has the best price.

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Rough idea- Exhaust $500, k&n $45, Hotcam Stg 2 $140.

I personally prefer the sparks foam filter, and use an outerwear with it.. that setup always worked great for me.

i was kind of speaking 450 language there about the k&n. sorry. i'm on the asking side of this. if the foam filter worked good that's what i want to hear.
is it okay in the sand with the outerwears? i'm assuming you ran without the lid? thanks

Foam filters suck in the sand thats all there is too it. I prefer foam in any other riding condition but if all your doing is sand riding like I do then the foam is a nightmare and I'll stick with k&n style filters. If properly cleaned they wont give you any problems at all. I've never tried foam with an outwear on it though and I actually didn't even know you could do that. The filter oil doesn't clog the outerwear all up?

I run HCII, 11:1 stock bore, K&N, and R4 exhaust on my 400ex. Its not going to run with a drag 450 but with a good rider it keeps up pretty good

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