after full day test run this pipe is perfect for the 660. power was crazy dow low and in the midrange. we where in the mountains most of the day so full thottle did not get chance.
but the few times i did she was gone. riding with 4 friends and the all agree that pipe is perfect sound for this machine.
it would wheelie in hi 4 wheel drive. not really wheelie guy but made big differents. felt like different machine. really mean sounding perfect for the grizz. hfm send me dyno sheet fri so if anybody wants one send me a e-mail to this address.
never heard a big gun so not sure what the differents. stock jeting was pretty close.

k/n filter 98-02 tight fit three new one in the works i hear.
dyno jet kit settings
155 main
there needle 4th notch
air screw 2 1/2 turns out.
needs minor adjustment because it ran even better cold. but it was smooth all day. just feel with a minor adjustment will be even better.

if any body wants a dyno sheet heres the address and i will send you the graft.

busawon@webtv.net

best sounding pipe i ever owned. AND AT 189.OO THOSE GUYS ARE FAIR. WELDS ARE VERY CLEAN. LIKE I STATED THE SOUND IS AWESOME.

 

It isn't too loud? I returned two HMF pipes for that very reason, one for my son's Raptor and one for my DS. If they made it somewhat quiet that would be great, but I can't imagine having a loud muffler on a utility quad, despite the increase in power. I do agree they were nicely made and a good value, just too loud.[img]i/expressions/face-icon-small-cool.gif[/img]

 

I was just wondering you said that this pipe wasnt too loud? I heard someone else mention a quiet core that HMF offers did you also have this or just a straight pipe? Im looking into an HMF for my Raptor and once I get one maybe even my future Grizzly if the sound isnt too loud!

'01 Blue Raptor- Stock

'99 Green Wolverine- Sold waiting to see if a Blue Grizzly is coming out for '03

 

louder then stock but sounds real nice on the 660. had supertrapp and fmf this pipe wins hands down. hopping to jet up to 165/175 main .
like i said feels like new machine, and i ride near houses and power lines not much different then my friends supertrapp and fmf pipes. deeper sounding tone perfect for big grizz. anybody wants to check out the dyno sheet heres there web site.
hfmengineering.com or there # 216-631-6980
stock weight was 11 lbs theres ws 5 lbs. very nice fit and very well made. after my friends seen the pipe and heard it they both wanted one for there rubicon and poloris no such like . seeems from there web site they have alot of experince with the raptor. also list for the 650 kaw.

 

I have the HMF on my Raptor. At first I bought the silent core but it is basically the same power as stock so I removed the airbox lid and that woke it up... not too loud either. I then ordered the real flow-through insert for the muffler and power went way, way up but so did the sound level. I replaced the airbox lid and it has a ton of torque and midrange. It is definately louder but it really roars!

 

Xplor,

You'll have to excuse me it may seem like im asking the same questions here but I just want to make sure I have everything right. (I havent found anyone that has a Raptor and the HMF system yet so im kind of excited) So your saying that with the pipe and the silent core you couldnt tell much difference from stock until you removed the air box? At that point with the quiet core was the noise level tolerable? I only ask because if I go and get this pipe im not sure if it will be appropriate to take up to Iron County in Wisconsin and ride around with. And then I guess how loud was it when you put in the flow through core? I think ive already figured that if anything I could get the quiet core for when I go up to Wisconsin (If the noise isnt too loud) and then just switch back to the flow through core when im riding around my own property? Any input on the sound difference's would be greatly appreciated.....Also your opinions on what setup makes the most power im just curious. =-) Thanks

 

FoxRunner. No problem, I am here to answer your questions. When I first ordered the HMF full system I had them send me the quiet core model. It has about 4 or 5 half-circles welded inside the muffler. I also put in a DynoJet kit. I jetted it according to DynoJets' specs but with the quiet core it was running way too rich because of the baffles inside the exaust. I have to admit that the sound is pretty amazing with the quiet core. It just has a special tone to it but not louder than stock. Since it was running rich I took the airbox lid off and tried her out...wow! That really woke her up and didn't add a lot of noise. Just a bit more coming from under the seat. Maybe if I were of jetted down and leaft the lid on it would have been fine too. Basically I noticed a gain in torque and mid.

Since I am a power-monger I decided to call HMF to send me a flow-through core. I wanted the most power possible. I think they only charged me 25$ more... The power did go way up but so did the sound level. It's the kind of 4-stroke thunder you can hear at 1000 feet! It is nice for where we ride because there are no homes but in noise sensitive areas the quiet core might be the trick. I just wonder if HMF could put in less baffles and go half-way??? Maybe a possibility.

I also called DynoJet and this is what they told me: "Any type of quiet exaust with baffles will not increase power tremendously but once you get a flow-through exaust then it become very noticeable"

If I were you... and not too sure... I would get the full system with quiet core and just order the flow through core and test both. For and extra 25$ or so it may be worth it. Just pop some rivets off and change the core.

Sorry, I kind of got going there...

Full system (flow through)and DynoJet = tons more power and noise
Full system (quiet core) and DynoJet = more power than stock with not too much more noise at all. Well worth it anyway in my opinion.

 

Xplor,

Thanks ALOT! You really cleared up alot of stuff for me. From the sounds of it I think I may just go the way I initially was thinking and get the HMF. And just do what you suggested and get both core's for it! As long as you say the power increase is still worth it with the quiet core....So in your opinion would you run with the air box lid on or off? Maybe ill have to do some experimenting myself. Jet down WITH the air box and jet it WITHOUT the airlid. One other thing I forgot to ask was did you get just the slip on or the header system also? Im looking at getting the full system the slip on AND the headers. Just wondering if maybe that had any effect also? I greatly appreciate your time and input on this! [img]i/expressions/face-icon-small-happy.gif[/img]
Also I was looking at their website can you get the pipe in just an aluminum finish? If so I think im sold on the HMF!

'01 Blue Raptor-Shockwears, Handguards, STOCK
Sold '99 Wolverine in hopes of '03 Blue Grizzly

 

FoxRunner, I am by no means a jetting expert, but from what I could see it runs smooth with the same jetting with the flow-through core and airbox lid on as with the quiet core and no airbox lid. At first I jetted to the specs of a full race system but with the lid on and quiet core... she was too rich and bogging down, but taking the lid off woke her up. Then switching to the flow-through core I just popped the lid back on but added a home-made 3" unifilter on top. Kept the same jetting.

By the way, I have the full system with the HMF headpipes... all aluminum and stainless steel, silver color. WOW!

 

just did pipe on my friends 660 grizz. tried some airbox mods and with the stock tires it's a wheelie machine.