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SumoWR

06 WR450 Tuning help!

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I know this topic has been beat to death on many many forums, but I can't seem to get te right answer or combination. I'm getting EXCESSIVE popping on decel. As soon as I let off the throttle it sounds like someone is unloading a 30round mag from an AR15.. Here's the specs,

06 450, AIS removed, yz throttle stop, g2 throttle tube and cam, white brothers E2 slip on,

Elevation is average 260ft. Jetting is JD 170 main, 48 pilot, Scott's fuel screw at 1.5 turns. Accelerator pump is wired, gray wire mod.

I've put a new head pipe washer in and cleaned the carburetor twice, no difference. AIS plugs seems to be fine, tightened them all. I haven't messed with the ACV (air cut off valve) or checked the exhaust /intake valve clearances. Just bought the bike used and can't seem to get it running correctly. Bike doesn't have any "bog" but it will not idle or run worth a flip until it's reaches 150degree coolant temp (trail tech reading). Which is usually idling on choke for a minute or 3. Once it hits 150 it'll idle fine. My normal temps here in Arkansas are around 80-95 degrees. thanks in advance to anyone that can help me before I light the bike on fire and walk away!

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 Many times the pilot jet is difficult to clean correctly and needs to be replaced by the way. If that doesn't do it try a larger pilot jet or two and see how the popping is and how it runs.

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The Scotts fuel screw is alloy?

If so dump it fo a brass one like R&D.

I'm willing to bet your hot start is the issue; not closing or a cracked nut.

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I replaced the pilot with and brand new 48 and it had the same issue, I just replaced the hot start nut due to it being crack when I got and and replaced the plunger and seal while I was at it. Fuel screw is the brass Scott's T-handle, o-ring in place. I guess I'll order a 50 and 52 pilot for kicks and try that. I'm also using the JD red needle

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A bigger piot is not the answer

You should never need larger than a 45

Either the passage above the pilot is still partially clogged making you lean or your acv valve is stuck shut or some othr lean condition

You should still have the original pioit air jet too

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I was following JD jetting guide lines with the 170 main and 48 pilot as a starting point. It also has an upgraded air filter. No that it makes much difference. But, I'll take it apart and clean it a third time and see what happens. Just can't help but think it's something other than jetting at this point.

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I've read often that people have used the 50 and 52 with no issues. That seems excessive for a stock bore bike but it is what it is. I'm going to give it a whirl and also check the ACV diaphragm/possibly do the mod.

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I've read often that people have used the 50 and 52 with no issues. That seems excessive for a stock bore bike but it is what it is. I'm going to give it a whirl and also check the ACV diaphragm/possibly do the mod.

 

If you do the mod you might epoxy the holes in the side of the carb then you need to run a YZ450 100 pilot air jet.

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Had the same issue recently. It was the hot start cable boot wasn't seated properly on nut. My fault, had it off while installing fuel screw and didn't put back correctly. Had a lot of real loud popping on decel. I have an aluminum nut and ended up using a little Vaseline on the boot so it slipped over the nut properly and then screwed it in. Popping all but dissapeared.

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