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99' XR 400 jetting problems

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I have a friend with a 99' XR 400 that has a bad bog. Off idle to mid there is a bad bog. We live at 900' and ride from 900' to 5500'. Any ideas? What should his pilot jet be, needle position, and main jet be to get a good base line for jetting? He did buy one of those deals that goes off the stock exhaust to open it up. Should he keep it open or just put it bact to stock? What diffrence does it make either way? He wants the noise but he also wants to keep it reliable. Any help in this matter would be great! 😢

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That was awful nice of you to say. Geesh all I asked about was a little help. If he puts it all back to stock what would be a good base line for jetting? Better? 😢

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Many of us are against making bikes a lot louder.

It just makes everyone but the rider angry and usually doesn't help that much with power.

The problem with your friends bike is probably that it is lean due to the modified exhaust.

If he wants to use the Stock exhaust, check out Gordon's Mods.

How to modify the bike and rejet it.

If he wants to read about the bog, check out my FAQ.

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I know. I tried to be as tactful as possible without saying what I really feel. Loud bikes and other irresponsible behavior is something our sport can no longer afford, as it's getting our riding areas shut down and turning public opinion against us. You guys live and ride in Washington State. I'd love to have the riding areas you do rather than these flat plains of Texas and scrub brush. I have to drive 8 hours to get to terrain like what you have.

As far as I'm concerned, if your friend wants to run an open pipe because he thinks the noise is cool or some other crap, I hope he nevers gets it running right or better yet, burns it up. Sure I could give specifics to help him out, but why should I help someone contribute to one of our sports current problems.

That was awful nice of you to say. Geesh all I asked about was a little help. If he puts it all back to stock what would be a good base line for jetting? Better? 😢

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The biggest problem with the XR400 since its release has been its jetting and it still hasn't been rectified.

With my 2000 XR400 (stock engine with baffle/airbox snorkle removed and carb insulator matched to head) I ran the following jetting/mods-

-158 main jet (2 sizes leaner than stock on oz bikes)

-55 pilot jet (stock on aussie bikes)

-Needle, middle clip position (stock)

-Airscrew 2 1/4 turns out

-Float level 15mm

-I also fitted a 15mm length of carby breather hose over the pilot jet to deepen its pickup in the fuel by 5mm, this helped with the spluttering over rough ground.

-other than checking these few things, check the other obvious things like dirty aircleaner, dirt in carb, valve adjustment. It might take you an afternoon in the shed but it'll be worth it!

Hope this helps

Mark.

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I know. I tried to be as tactful as possible without saying what I really feel. Loud bikes and other irresponsible behavior is something our sport can no longer afford, as it's getting our riding areas shut down and turning public opinion against us. You guys live and ride in Washington State. I'd love to have the riding areas you do rather than these flat plains of Texas and scrub brush. I have to drive 8 hours to get to terrain like what you have.

As far as I'm concerned, if your friend wants to run an open pipe because he thinks the noise is cool or some other crap, I hope he nevers gets it running right or better yet, burns it up. Sure I could give specifics to help him out, but why should I help someone contribute to one of our sports current problems.

That was awful nice of you to say. Geesh all I asked about was a little help. If he puts it all back to stock what would be a good base line for jetting? Better? 😢

I know where your coming from but some of us ride on PRIVATE land too. We can do what we want on private land. I don't want to get into a pissing match with you, I just wanted to know a good base line for jetting. He is thinking about getting rid of the XR and buying a WR.... Thanks for your help though.... 😢

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I don't want to get in a pissing match either. I don't usually come off with such an attitude.

Running open pipe means running no spark arrestor either, and fire doesn't distinguish between public, private or federal lands. So riding on private land is no excuse.

I know where your coming from but some of us ride on PRIVATE land too. We can do what we want on private land. I don't want to get into a pissing match with you, I just wanted to know a good base line for jetting. He is thinking about getting rid of the XR and buying a WR.... Thanks for your help though.... 😢

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I'll give credit where credit is due.... I never thought about that. Thanks! 😢

Now with that out of the way I will let him know to go back to stock and we will TRY to get this bike tuned in. Let the headache begin!!!! 😢

EDIT: I just talked to him and the kit he bought does come with a spark arrestor. Just thought I would say so... 😢

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>He did buy one of those deals that goes off the stock exhaust to open it up.<

That doesn't help much. Would be best to know exactly what it was he put on there. Also need to know if he has pulled the snorkle or not and if he's running an aftermarket air filter. It all makes a difference in what jetting to suggest.

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I believe everything else is stock. It's a "Billet" end cap with a screen. He pulled out the baffle and then this end cap screws in place of the baffle.

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Tell your bud that putting the new end cap on there is pretty much a waste as far as performance goes, by itself anyway. If you make the exhaust freer flowing, in order to see any real performance increase and not create a screwy jetting nightmare, he really should pull the snorkle under the seat to increase intake airflow as well. Then, for the altitude range given, I'd start with a 155main/55pilot and readjust the fuel screw for best idle and throttle response between 1.5- 2.5 turns out. Needle 3rd from top(middle).

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