Which HMF?

[Melton69]

Hello,

I am looking to get some power out of the 400 cause its sluggish on the sand. I am still wanting to keep it reliable so no major work going to be done, thats what my 250r is for...

So far I am looking at sparks 6* timing key, K&N w/ prefilter, airbox removed, a good slip-on and grinding the welds on the header. Maybe going a to a 14T front sprocket.

My questions are:

Is a HMF slip-on a good choice for this setup? I might eventually get a stage 2 hotcam.

Also, I noticed that they have two models, has anyone tried the new competition series?

[Bwetzel55]

I just ordered the competition series slip-on. Heard that it has more performace than the other hmf series ones. I'll let you know how it is once it comes

[Melton69]

Whats the difference between the two? I dont plan on changing the insert. They dont say on their site that there is any difference between the two, and I dont plan on needing to restrict the airflow so the insterts dont matter.

[mtrombla08]

well i just ordered one of the new competition full systems as well. i hope it will add alot. i will let you know once it is put on. about the regular hmf. if u buy a slip on make sure that is what u want. i had one on my bike and just sold it to go to a full system. if u buy the slip on u cannot upgrade to the head pipe later. the pipe the comes with the full system isdifferent in size to just the slip on. i would recommend goin with the full system. i was cheap and just bought the slip on and it didnt give me enough. you will still be loosing flow because the stock head pipe is so much smaller.

[unitednations]

my hmf sucks. the rivets are coming out. i wish i wouldnt went with hmf!

[rob_990]

Originally posted by mtrombla08
well i just ordered one of the new competition full systems as well. i hope it will add alot. i will let you know once it is put on. about the regular hmf. if u buy a slip on make sure that is what u want. i had one on my bike and just sold it to go to a full system. if u buy the slip on u cannot upgrade to the head pipe later. the pipe the comes with the full system isdifferent in size to just the slip on. i would recommend goin with the full system. i was cheap and just bought the slip on and it didnt give me enough. you will still be loosing flow because the stock head pipe is so much smaller.

a header wont do much unless theres motor work done to it and if you wants to upgrade later you can get the fmf powerbomb header

[KBROOKS400ex]

Originally posted by rob_990
a header wont do much unless theres motor work done to it and if you wants to upgrade later you can get the fmf powerbomb header

X2 headers don't do schit. If you were going to do a port and polish and bored out cylinder i would get a full system. Also what hmf says about there HP increase its not true for a ATV to get a big HP increase you have to mod the engine.

[IcutMetl]

Originally posted by unitednations
my hmf sucks. the rivets are coming out. i wish i wouldnt went with hmf!

Amen! I know a lot of people on here really like their HMF's and just like me, are entitled to their opinions- hopefully based on experience. I bought an HMF when they first started coming out for the 400ex, and compared to my Yoshimura RS3, was disappointed in every aspect of it- horrible fit and finish plus narrow performance band. HMF is headquartered about an hour or so away from me so I thought as a bonus it would be like supporting a local business- sorry guys, if I ever have another 4-stroke, it'll have something else on it.

[unitednations]

i think my pipe is causing my 4 wheeler to pop when i let go of the gas due to the rivets coming out. I might just buy and other brand slip on and use it with my hmf headers.


or wait you cant use a slip on with a aftermarket header?