what im gathering after performing a search is this about the hmf pipe. i just bought the full exhaust system hmf sells and my stealership will be rejetting for me and instaliing it. what im gathering is it will be a big gain in performance compared to stock. is it true though hmf are loud and they give it more top end than low end, im also having them adjust the valve clearance since i didn't have them checked after the break in period

04 raptor 660 few mods

 

Any kind of aftermarket pipe will be loud on a 660, and hmf is one of the louder pipes out there.

I don't know where the hmf adds more power on the raptor, but on my warrior I noticed a bigger gain in low end power.

 

I had a full HMF on my 05, along with a Pro-Flow K&N (no lid) and Dynojet kit. It pulled strongly throughout the whole powerband, all the way to the redline. I'm not sure how it compared to other pipes but I never lost to another piped Raptor in the short time I had it. If you get the jetting right, the 660 can be a real **** with just these simple mods. I'm sure your dealer will jet it accordingly but they would have to be really good to maximize performance in one shot. I had to tear my down 5 or 6 times to get the jetting spot on, right where I wanted it.

 

I also have the hmf full exhaust, its a pretty loud pipe, i can hear it from around two miles away. big power gains in the upper gears, and also a noticeable amount in the lower gears. the raptor doesnt need any more low end power anyway, even though the low end power gains are not great on the shift from first to second the front wheels just rip off the ground. u should remove ur air box lid and look into a pro flow or GYTR air filter and adaptor plate if u want a couple extra hp. the hmf is a good reliable pipe.

 

thanks guys, im chopping at the bit to get it back, it should be out by wed sometime. right now i have a k&n filter on it inside the stock air box, im kind of scared to run anything else due to riding in the mud allot

 

hmf is a decent pipe, you will be happy with it. i would rank it like 4th or 5th best pipe available for the raptor.