2008 WR450 with JD Jet kit makes a "FFFFFT" sound

My brother in law and I were helping a friend of ours install a JD Jet kit on his brand new WR450.

We removed the snorkel, took out the exhaust baffle and installed the blue needle, 4th clip from the top and the #170 main jet and replaced the pilot jet with the one in the kit, #45 I think. Elevation is 600 ft., temp around 65 degrees, MSR fuel screw, 1.5 to 2.0 turns out.

The bike runs fine and response is good, but on decel or after a quick rev, the engine sounds like it's missing and makes not a backfire but a "FFFFT" sound.

He didn't want the AIS removed so we left it. I don't remember the JD instructions saying to remove it.

Checked carb intake boots and they are tight, no popping on decel either, just that occasional "FFFFT" misfire.

Thanks!

CO,

LOL, it's tough to replicate a sound on here, isn't it???

Did your bike make that "FFFFFT" sound constantly or occassionaly? My friend's bike just does it occassionally and during quick revs. No bog.

Thanks man!

Karl

It's not really "constant," but it is "routine," while riding. It was annoying enough that I bought and installed the Promoto Billet tip.

I didn't really notice any performance changes, but I no longer notice any exhaust sound while I'm riding. (Still laughing. :thumbsup: )

I think you need to make a wave file of that sound so we can link to it and listen :thumbsup:

I think you need to make a wave file of that sound so we can link to it and listen :thumbsup:

I'll have it for you in a little while...just need to let my lunch settle, first. :eek:

LOL, I call that 'exhaust sneezes'. Open the fuel screw a little more, 1/2 to 1 turn more and see that that reduces it some

Mine was most noticeable under a load, that is, while riding it.

Hey karl i think it was a 48 pilot jet and thanks again for your's and Joe's help sunday.

make that sound again.

make that sound again.

PFFFFFFFFFFFT! :thumbsup:

Mine was most noticeable under a load, that is, while riding it.

Thats the FCR carb. They all do it with a quiet enough exhaust and an opened up airbox.

My cousin had a loud ass pipe on his YZ 250f and he couldent hear it. As soon as he quieted his exhaust down he's heard it every time he rolls on the throttle.

I know husabergs are few and far between, but the next time you see one pay attention to how it sounds under load. They have no airbox (they use the back bone of the frame to place the airfilter) and they sound pissed off when the rider is on the gas

Pay attention to the way the engine sounds at 1:02

Thats the FCR carb. They all do it with a quiet enough exhaust and an opened up airbox.

My cousin had a loud ass pipe on his YZ 250f and he couldent hear it. As soon as he quieted his exhaust down he's heard it every time he rolls on the throttle.

I know husabergs are few and far between, but the next time you see one pay attention to how it sounds under load. They have no airbox (they use the back bone of the frame to place the airfilter) and they sound pissed off when the rider is on the gas

Pay attention to the way the engine sounds at 1:02

On the WR, if you completely remove the exhaust tip via the four allen-head machine screws but leave the outside exhaust "shroud" on, you get a more distinct sound in the exhaust. Installing the Promoto billet exhaust tip doesn't really change how loud the exhaust is, but it gets rid of the annoying "hissing."

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