Just an update..... I tried as high as 185 main jet and still having problem 3/4 - WOT. So I put the stock jets, stock pipe, and air lid back on. This after I cut my air lid like the hrc kit lol, so I had to get the duct tape out. Fired her up and she runs like a champ. I have a trip planned to Wayne national forest for Memorial day weekend with the guys. So I took my quad to the dealer to have them jet it (which is what I should have done in the first place). They said they are backed up and may not get it done by next Friday. So at the very least I will get to go, but may be going stock. I was really looking forward to Burrwwapping through the woods, but I'll have a blast regardless. I'll post the results when the dealer does get the hmf pipe and jetting to work on it. They are charging me $110 :-( Thanks for the help everyone.

 

Atleast you know something is not broke or screwed up. Try this site for more info on your pipe and jetting.
http://www.hmfengineering.com/forums/index.php
I would have to think being it's happening around 3/4 throttle that it in the needle adjustment. I'm pretty sure that hmf uses Dyno jets in there kits. Alot of old 450r owners say throw them away and use geniune keihin jets. I did a little research and used the adjustable needle from a 04-05 CRF bike. The same engine ours was designed after. Put it on the 3rd clip with a 170 main and lookout!! You might try that as your last try. Just go to the parts counter and tell them to order it for you. It's about $8-10. I'll bet my left you know what it will fix your problem.[img]i/expressions/face-icon-small-happy.gif[/img]

 

I purchased the adjustable needle from hmf. I had it on the 3rd clip down. I've been all through the HMF forums and contacted them on the phone. Still no luck, that's why I decided to let the professionals do it. But yeah, I was so relieved when I got it back to stock and it ran fine. Took it down the road full throttle and it was flawless. I was a little worried that something major or expensive was wrong.

 

Ok taking my stock 06' 450er and adding a slip-on HMF sport pipe, I was having a problem with 3/4 - WOT with the recommended HMF jet adjustments. For a simple fix just throwing the pipe on and not changing anything worked fine with the air lid on. Taking the lid off or cutting it like the HRC kit and running a K&N air filter with outerwears made me jump from a stock 120 main to a 180-195 main. As a reminder, I also installed a bigger pilot jet (not sure what size), an adjustable needle with the clip 3 down from the top, and an adjustable fuel mixture screw about 2 turns out. So for now, I'm leaving the stock air filter on with the full lid covering it. I am taking a big trip to Wayne National forest this weekend and we have had a ton of rain lately so I don't want to run without a lid in all the mud and water. My dealer highly recommends leaving the air lid on and didn't have anything good to say about K&N air filters. He did convince me to get the HRC kit though, but I'll wait till next summer for that. I spoke to the mechanic personally and he told me if I run my quad w/o the air lid w/ a K&N filter even with the outerwears I will be replacing the top end within 6 months. He said that K&N filters let in 70% more air than a stock filter which means more dirt getting into the carb and engine. Anyone have a different opinion on K&N filters? Should I go to a Uni or different type foam filter, or just stick with the stock air filter?

 

If you install the HRC kit then you MUST run without the lid. I'm using the k&n filter with no problems. For added protection I took an old pair of pantie hose and streached it over the lid. It fits great and catches most of the dirt before it enters the airbox. Using the stock filter requires you to use that restrictive core inside the filter. I got a pro flow design billett that takes care of that problem. Plus it sounds a lot meaner with the lid off, Just keep an eye on your filter and keep it clean.