I have an Arctic Cat 400 4x4 Manual trans. this is my wifes bike. We went to the hat-field Mckoy trail system in West Virginia the first of this month. I noticed a knocking sound coming from what I thought at the time was the motor, but after driving 10 hrs from georgia just to ride the trails it was gonna have to blow up before I loaded it up to bring it home. It ran fine the whole week we were there except for the knocking sound. after we got home I traced the sound to the fuel pump{i believe thats what it is}. It runs perfect. I'm wondering if anybody else has ever had this happen to them. i can get a new fuel pump for $28 but im not 100% sure thats what it is. Thank you,
daniel

 

my fuel pump makes noise to. i have an 07 500i man. it has 2200 miles of hard riding on it and it has made the noise since purchased new.

 

Yeah thats how this one is. We bought it new in 07 and it was my bike and I noticed it but it seems like it got louder this time. I guess as long as it runs like a/c meant for it to I'm not going to worry about it {unless my wife starts busting my ***** about it}. I hope my 08 650 H1 doesn't start making the same noise.
Thanks for letting me know that yours is making the same noise as mine does.
Daniel