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idamoh

08 WR450 Running Lean?

9 posts in this topic

I've got an 08 WR450 with the following mods: YZ Throttle stop screw, binoculars removed, Stock exhaust with 45MM tailpipe instead of the 29MM w/baffle. I have not cut the gray wire or removed the AIS. I ride at around 2000-4000 feet.

As far as jetting goes I am running a 162 main jet, and a 48 pilot. Everything else is stock.

I get backfiring and sputtering at 1/4 to 1/2 throttle. It runs great at full throttle. Do I need a new needle jet, or a bigger pilot? I've tried running bigger main jets all the way up to a 170 with no luck.

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1. remove the grey wire. it takes 2 min. and is very nice.

2. what clip position are you running on the needle jet needle? I guess if you still have the stock smog needle you can't move the clip, but I've heard that you can put a washer under the clip to raise is about a clip possition, which will rich it up a bit.

3. add a fuel screw. set it to 1.5 turns. it interacts with the pilot jet, you can use it to see if you pilot jet is the wrong size. I run the stock pilot.

4. add O ring to the AP spring

FYI: When I jetted my 08, I like to take the top motor mount off to get to the top of the carb. It’s very straightforward to remove and makes it easy to get to the needle.

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From all that I have read power from bottom, mid to top end corresponds respectively (+/-) Pilot, Needle, Main. So you could try the larger pilot and should see a difference. If DEMO SLUG is right...you could back the fuel screw (bottom of the bowl) out 1/2 a turn at a time and see if that gives positive results first...cost is zero pesos.

EDIT...backfiring...remove the AIS like Kevin said

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I had this problem and it was solved by removing the AIS. No more backfire at all. Ten minute's and 35 bucks well spent!

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Cutting the grey wire also allows the ignition timing curve to match the bike going to wide open throttle after the stop has been cut or replaced. Depending on where you live and ride in Cali, I would not run anything smaller than a 168 MJ. If you are up in elevation then 162 may be OK. Look into disabling the AIS versus removing it. I have read that it's something the rangers are now looking for.

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I'll try cutting the gray wire, and adjusting the fuel screw. If that's doesn't help maybe I should go with a bigger pilot.

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I'll try cutting the gray wire, and adjusting the fuel screw. If that's doesn't help maybe I should go with a bigger pilot.

IF its backfiring on decel remove the AIS and it'll go away with your current setup.

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If DEMO SLUG is right...you could back the fuel screw (bottom of the bowl) out 1/2 a turn at a time and see if that gives positive results first...cost is zero pesos.

:prof:

actually that is from the Zip Ty fuel screw instructions. its only $24. and comes with instruction on how to install it and what to do with it after it is installed( which was a big help to a jetting noob like me). and comes with a cool little sticker too:applause:

but the reason I recomend the fuel screw is that it is so tuff to get to it on my WR. the starter is in the way. its real tuff to to keep count of how many turns when I'm not even sure that I have the screw driver engaged with the slot:excuseme:

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I' m riding #175:MJ OBDTR-4:Needle #50:PJ #45:LJ and #110:MAJ. No problem at all. Yes, it is GYTR kit.

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