Engine/exhaust weird sound? (WR450F Supermoto)

My engine/exhaust has developed an odd noise while both on an off throttle, it seems more so apparent while on overrun. It's a hard one to explain but I'll try: imagine recording the sound of your exhaust then playing it back on two separate devices but ever so slightly out of time, so it almost sound like two exhausts. Bike seems to run OK but here's some info:

Bike: '03 WR450F Supermoto (European Spec)

Engine: YZ Exhaust Cam, manual tensioner, Twin Air filter

Exhaust: Akrapovic EVO Ti system

I had it jetted last year (by a guy I trust) when the exhaust cam was fitted, he did it by ear/feel but retained the original jets. It ran and sounded fine after that but has started sounding odd lately. So I'm wondering if the standard jets aren't enough for the mods or maybe it's running lean?

You guys have any ideas?

Edited by RipGroove99

Would exhaust valve clearance cause this if out of spec?

It's either jetted right or it isn't.

Have you ever adjusted your fuel screw?

TPS?

Replaced you Needle jet?

Adjusted you intake valves?

It's either jetted right or it isn't.

Have you ever adjusted your fuel screw?

TPS?

Replaced you Needle jet?

Adjusted you intake valves?

Well it runs fine I guess, whether its yz cam fast or not I dont know as I have nothing to compare it to. Valve clearances were in spec last summer when the cam as fitted. Other than that all I've done to it is unplug the tps? Little grey plug up by the seat on the left side of the bike as it never used to like being held at constant revs. Its a supermoto now so that was a real pain on the road. Its only recently its been making this odd sound.

My exhuast began to sound "funny," but still ran ok. The sound bugged me to the point that I took off the exhaust can to see if something was amiss. Turns out that all the packing had vanished. Repacked and everything back to normal.

If the bike still runs fine I'd suggest the packing in the exhaust as well.

How he got it "tuned" using the stock jetting I will never know, though, as even if you kept the bike stock it's generally lean. UK tune may be different, though. Are you the original owner? Are you sure he didn't use what was already in there (and the PO may have jetted it) and not actual "stock" jetting?

Regardless, check the muffler packing.

Mike

If the bike still runs fine I'd suggest the packing in the exhaust as well.

How he got it "tuned" using the stock jetting I will never know, though, as even if you kept the bike stock it's generally lean. UK tune may be different, though. Are you the original owner? Are you sure he didn't use what was already in there (and the PO may have jetted it) and not actual "stock" jetting?

Regardless, check the muffler packing.

Mike

Thanks, but I'm pretty sure it's not that as I keep on top of the packing :-)

If the bike still runs fine I'd suggest the packing in the exhaust as well.

How he got it "tuned" using the stock jetting I will never know, though, as even if you kept the bike stock it's generally lean. UK tune may be different, though. Are you the original owner? Are you sure he didn't use what was already in there (and the PO may have jetted it) and not actual "stock" jetting?

Regardless, check the muffler packing.

Mike

I'm the second owner, I believe it's still on stock needles. When I bought it it was doing a lot of popping and banging on overrun so had my local Motorcross guy have a play with the carb until he got it pulling nice and smooth and got rid of most of the popping and banging. He then fitted a YZ exhaust cam for me and the bikes been fine until recently. So, do I need a JD jet kit or something as I'm guessing the stock needles are no good for a race pipe and bett cam?

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