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450_James

Jetting problems??

8 posts in this topic

Info: 05 WR450 JD jet kit, blue needle #4 position, 170 Main Jet, Airbox snorkel is out, right side airbox holes cut out, Sea Level riding (mostly)

Problem: When starting with the choke out, the bike starts ok. I went down the street with the choke out by mistake and on acceleration the bike was coughing and sputtering. It was still a little cold but I pushed the choke in and it seemed to run strong.

Am I on the edge of a problem here? Before the choke would just rev the engine higher, now it doesn't sound so good.

Any help would be appreciated as I've got a ride in the morning.

Thanks,

450_James

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I dont think you have a problem, sounds normal to me. I am running with similiar mods to my bike, it will do the same thing when cold, but runs great when it warms up. I cannot run my bike down the road with the choke on at all.

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Alright. If all else fails read the directions. Except if you have a WR450 don't read the instructions for the YZ450. :cry:

The directions that come in the JD kit have two sides. One side for the YZ and the other for the WR. They are almost the same aside from the YZ side says blue needle #4 position. The WR side says blue needle #3 position.

I dropped the needle setting to the #3 position and will ride it at the break of dawn.

Thanks for the reply RDR I'll let ya know how it goes. You may want to try the same as me on this because I hardly got a responce from the mixture screw adjustment with the needle at the #4 position.

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450 James, I went by the instructions for the WR (clip on 3rd groove) on my jet kit and same thing, not too much change when messing with the mixture screw. I ride 1000' and up but I have been told to lower down my clip to the 4th from top position. Just haven't had a chance to do it yet. I have a 170 MJ, a 48 PJ, snorkel still in, one out of two holes on RH side of airbox cut out, stock exhaust uncorked, grey wire mod, and thottle stop screw cut down. If I get it done anytime soon, I'll post and let you know how it worked for me.

I have noticed that these bikes warm up waaaaaay faster than I knew a four stroke could (I was used to my uncles XR400 taking forever to warm up enough to turn choke off and be able to rev it without killing the engine...). I am starting to think that I have been chasing a problem that didn't really exist as far as the light popping sound that I was calling a "backfire" on deceleration. Seems to be that this is not related to the carburetion but more so related to the AIS system. see this thread

Now once I get the off-idle hesitation to go away and get the AIS block kit, I should be golden! Hope some of this may have helped..... :cry:

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450 James, I am running aftermarket exhaust which is not listed in my sig, the bike absolutely rips the way it is set up, response is great.

what I don't see in your setup is which pilot your running, is it still stock? I am running a 48pj now.

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450 James, I went by the instructions for the WR (clip on 3rd groove) on my jet kit and same thing, not too much change when messing with the mixture screw. I ride 1000' and up but I have been told to lower down my clip to the 4th from top position. Just haven't had a chance to do it yet. I have a 170 MJ, a 48 PJ, snorkel still in, one out of two holes on RH side of airbox cut out, stock exhaust uncorked, grey wire mod, and thottle stop screw cut down. If I get it done anytime soon, I'll post and let you know how it worked for me.

I have noticed that these bikes warm up waaaaaay faster than I knew a four stroke could (I was used to my uncles XR400 taking forever to warm up enough to turn choke off and be able to rev it without killing the engine...). I am starting to think that I have been chasing a problem that didn't really exist as far as the light popping sound that I was calling a "backfire" on deceleration. Seems to be that this is not related to the carburetion but more so related to the AIS system. see this thread

Now once I get the off-idle hesitation to go away and get the AIS block kit, I should be golden! Hope some of this may have helped..... :cry:

10-4 on the warm up. About 30 seconds. I put the needle to the #3 position and I don't have the problem any more. And I am able to get a good responce from the mix screw. I read in another thread that the off-idle hesitation can be fixed by adusting the mixture screw (gotta get a Zip-Ty). Do a search on it. If your not getting a responce from the mixture screw it might mean the main jet is wrong. I'm not a pro at it so check it out.

Thanks for the input

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450 James, I am running aftermarket exhaust which is not listed in my sig, the bike absolutely rips the way it is set up, response is great.

what I don't see in your setup is which pilot your running, is it still stock? I am running a 48pj now.

Still stock and not sure how to change it. I'm assuming the JD kit doesn't include it as I didn't see info on it. What was your stock pilot jet?

I'm running the stock exhaust with the snokel removed. Saving for a FMF Power Core IV or maybe a Dr. D. I'm going to wait till that's on before doing much more fine tuning. But any info on the pilot jet would be great.

Thanks! :cry:

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stock on mine was a 43 even though the book says it should be a 45, I am at a 48 now, I am currently running the FMF powercore IV SA with or sometimes without Silent insert. A great setup which allows you to run in most areas and be legal.

The pilot can be accessed through the drain bolt on the bottom or you can just remove the bottom of the carb.

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