mild power

[boystoys]

i am looking to get as big as gains as i can out of my 400ex without crazy mods, like punching it out, stroking, cam work ect... the guy i ride with rides a CR250 and it hits HARD and we do alot of tight woods riding.. so i am looking for low end TQ so far i am looking at a HMF pipe, uni filter and gearing down the front to a 14T... not sure if i want to rejet or not..i probally should...but i have been told it never runs the same again...:(

so i am asking all the guys that have tried things and know what works and what doesnt before i go and waste my money...

[atvracr350]

First off i would say that you shouldn't ever listen to the guy that told you rejetting will never make your atv run the same again. He obviously doesn't understand the purpose of jetting a fourwheeler. With the mods you described (hmf pipe, uni filter,) your engine will be sucking in and blowing out way more air which equals more power. To make your engine run right you have to increase the amount of fuel the engine is getting also by changing your main jet. If you dont' change the main jet and get the pipe it would be a complete waste of money for the pipe and airfilter. If this is confusing to you then tell me and ill try again to explain it a little better. Basically if you get more airflow than you need more fuel flow. And by the way your mods including the 14 tooth sprocket will give you way more bottom end and i think you will like it. Hope i helped out.

[Toadz400]

Go with a full HMF system and gear down the 14t and don't forget to jet! Make sure to slap the guy who told you NOT to rejet.

[boystoys]

the guy that told ne not to said he rejetted his EX and it did fin on flat land but as soon is it was "off camber" like on the side of a hill it would cut out and sputter...


i understand that with a 14T sproket it will top out in 5th like toping out in 4h on the 15T is that about right?


and i totally understand about the jetting thing. is this something that can be done by me or should i take it somewhere and is there a good/better/best brand of jet?

where is a good place to get the HMF stuff from, i thought i saw a guy on here that sells um' .....


Thanks for the good input...:D

[nosliw]

Originally posted by boystoys
the guy that told ne not to said he rejetted his EX and it did fin on flat land but as soon is it was "off camber" like on the side of a hill it would cut out and sputter...


i understand that with a 14T sproket it will top out in 5th like toping out in 4h on the 15T is that about right?


and i totally understand about the jetting thing. is this something that can be done by me or should i take it somewhere and is there a good/better/best brand of jet?

well your friend didnt do it right. i noticed a huge power increase from low end to high end regardless of what terrain im on.

you can jet it yourself. buy individual jets, dont buy the jetkit they try to steal your money with. i used keihen jets.

[BOONE450R]

sounds like that guy who told you that messed his floats up.;)

[Toadz400]

Originally posted by boystoys
the guy that told ne not to said he rejetted his EX and it did fin on flat land but as soon is it was "off camber" like on the side of a hill it would cut out and sputter...


i understand that with a 14T sproket it will top out in 5th like toping out in 4h on the 15T is that about right?


and i totally understand about the jetting thing. is this something that can be done by me or should i take it somewhere and is there a good/better/best brand of jet?

where is a good place to get the HMF stuff from, i thought i saw a guy on here that sells um' .....


Thanks for the good input...:D

1. Your friend needs to clean his carb bowl, his float is messed up. ALWAYS rejet when you increase/decrease the flow of air/fuel/exhaust.
2. 5th gear will feel like 4th gear with the 14t sprocket, but it still rules for bottom end power!
3. You can rejet yourself, VERY easy to do, if you don't know what to do, go out and buy a manual.
4. C&D Racing (The site sponsor) sells HMF at a good price, and they offer GREAT customer service. Just make sure you go with the full system, not just the slip-on, you will end up regretting it later on if you plan on producing more power from your engine.

[boystoys]

does the full system take away some low end? i noticed some head pipes do...

[zccopwrx]

Full system will take some low end away, but add top end, but gearing down to a 14T will make up for the low-end loss. Overall you will just pull harder, which is what we all want anyways.

[Toadz400]

Originally posted by boystoys
does the full system take away some low end? i noticed some head pipes do...

Depends on what exhaust system you get, some give awesome low end, some mid-range power, and some just top end.

Throw in porting, bigger carb, big bore and you don't have to worry about the loss of low-end from a full exhaust anymore:D .

[zccopwrx]

I have a 14/38 w/chain set coming, should be here by this weekend, Ill post a follow up with how much different it feels.

[EXrider65]

I run a 13-tooth front sprocket and can stay up with anybody in the (WOODS) not on the highway as some of these guys ride. I live in a good hill area for climbs and such. I run in 2nd and 3rd alot and some times 4th but rare on the trails themselves. Also a Quicksilver carb helps and a few more things but no major engine work yet (haven't worn this 1 out yet). Good luck 2 each his own really when it comes to preference.