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97 xr400 cuts out

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I have a xr400 that runs good every where but on g-outs or very rough sections, it sputters right when you get back on the gas from a landing from a bump as small as 2 feet. Jetting is 62 pilot 162 main needle in 3rd clip, aftermarket filter and wb e series exhaust. If its smooth it responds to any throttle with great response. It has no bog on the stand either, Ive cleaned the carb several times and checked the air cut off diaphragm and circuit. I have had several xr400's over the years and this is the only one to ever do this. I picked it up for 800 dollars because the guy couldnt get it to run, A little TLC and she fired up first kick, but this sputter is annoying.

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Might be the float level as suggested.

Check the fuel feed into the carb too.

I put a clear inline fuel filter. Keeps junk out of the carb and I can see if fuel is flowing.

I am pretty sure the gas cap was causing vapor lock an causing my xr400 to die.

While checking everything else, check it so you don't have the next problem.

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I'm going to recheck float level, I think I have it at 14.5 mm but will recheck. I will check gas cap vent to, also anti slosh baffle is in place and in good condition. Thanks guys , this is driving me crazy ,it runs perfect around the house and then you hit some nasty trails and its awful.

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Sounds electrical to me, remove & re-fit all ignition related connectors one by one & test in between to eliminate bad/corroded connection. painful but worth doing if all else fails

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I'm going to recheck float level, I think I have it at 14.5 mm but will recheck. I will check gas cap vent to, also anti slosh baffle is in place and in good condition. Thanks guys , this is driving me crazy ,it runs perfect around the house and then you hit some nasty trails and its awful.

It doesn't sound like a fuel problem. Check for a bad spark plug wire, check the connection from the boot of spark plug wire to the spark plug it self and make sure that connection is good.

 

 

good luck

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I am leaning electrical as well. We bought an XR a few years back and previous owner had routed the wires under the seat right over the metal bracing- if you sat in just the right spot and bounced the bike you could get it to short the ignition and shut off the bike. Wiring on these bikes is so simple, pull the seat/tank/headlight and have a good look at wire conditions and routing.

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I think its the float. The max drop from the factory is set way too much. Its like around 25mm. Bend the tab on the side of the float arm so it contacts the float tower with a float level of only 5mm more than your minimm drop spec of 14.4mm, which would make your max drop 19.5mm.

On rough and g-out type terrain and hard landings from jumps, the float is suddenly forced downward, displacing fuel in the bowl. That fuel has to go somewhere. It gets forced out the overflow and it gets shot up the jets into the carb. The sudden introduction of raw fuel causes the stutter until it clears out.

In my Youtube carb video I show how to do set the max drop.

Edited by Trailryder42
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i just picked up a 97 today... it was hard to start and bogged off idle... 62/162 gordon mods, didn't check clip yet...

 

i always just set the float level (on multiple bikes) by holding the carb upside down with the float in place... adjust tab so that the molded plastic horizontal seam is parallel with the carb base (where the gasket meets up) this has cured many float related symptoms without taking the time to find the numbers... or being in the field...

 

the other thing is once the bike was idling on the stand, i could close the mix screw ALL the way and it was still running smooth... telling me the 62 pilot is too rich... i opened it 1/2 turn and its running fine, but will be getting a 60 pilot next time in...  took it for a test ride... fires up first or second kick now and runs smooth...

 

"SLOSH GUARD" eh???   i was actually coming on here to ask what that plastic thing was... it was cracked but i always just toss them in the extra part pile anyway... never ridden with it in during 5 years... and i ride a LOT of rocks!!!

 

speaking of rocks, a gratuitous post of one of my videos...

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i could close the mix screw ALL the way and it was still running smooth... telling me the 62 pilot is too rich. . . .

 

. . . . or the PO installed a 62 to make up for the fuel screw passage being clogged.  

 

On my 250, I found it starts best at 2 1/4 turns out (throttle closed) with either the 40 or 42 pilot jet, even though tuning it tells me 3 turns with the 40 and one turn with the 42.  I'm running the 40 now.  YMMV

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I rechecked float and found it a little off, set it as per TR42 video but have not had a chance to test ride yet. float height was 15mm and max drop was 21mm, now set at 14mm and 19.5 set by digital caliper inline with main tower.. Thanks guys, I will report back when I have a chance to test ride.  

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Got a chance to ride this weekend and the sputter on  g-outs is gone but still there on landings from 2' high water bars and from hoping off a 3' high step off over a small creek. I can wack it open on the stand like on my yz450 and no stumble at all but get it going and hit somthing hard at speed like a water bar or a long section of large rock and it spurters like crazy. I ended up parking it and riding my yz450 in the trails the rest of the day and was pleasantly surprised with the 09 full moto suspension . Also my sons xr , its a 02 has never done this either, it must have a gremlin.

Edited by mx614

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Basic question: What do you see in an xr400 if you have a YZ450?  I would really like to know.

 

My xr400 seems to run good but I don't tend to jump it.

Got a chance to ride this weekend and the sputter on  g-outs is gone but still there on landings from 2' high water bars and from hoping off a 3' high step off over a small creek. I can wack it open on the stand like on my yz450 and no stumble at all but get it going and hit somthing hard at speed like a water bar or a long section of large rock and it spurters like crazy. I ended up parking it and riding my yz450 in the trails the rest of the day and was pleasantly surprised with the 09 full moto suspension . Also my sons xr , its a 02 has never done this either, it must have a gremlin.

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I dont really jump it, I only ride trails and enduro / hare scrambles every now and then, but I was looking for something more trail oriented. I have had 4 other xr's over the last 15 years and none have had this problem. I ride at a vet B pace, kind of used to be fast but I'm 42 now but can still hang with my 16 yr old son at a B level. I could just ride my YZ450 I guess, but its pretty amusing to pass newer bikes on a old XR.  I would like to get it running right either way. Thanks

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Got a chance to ride this weekend and the sputter on  g-outs is gone but still there on landings from 2' high water bars and from hoping off a 3' high step off over a small creek. .

Do you have a slosh baffle installed? Ever found it laying in the bottom of the bowl?

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yes its installed and its a tight fit, stays in place when you remove the bowl. I think it might be possessed.Oh one other thing I was checking the fuel screw pilot relationship and found it runs best at 3.5 turns out and will slow down idle at 2 out and die at 1.5 out like its lean on the pilot with a 62 pilot installed. Thats what I've always ran in my xr400's. The last one I had was a 02 and raced it in the B class hare scrambles and it worked fine.

Edited by mx614

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Go another 5-10 on the primary jet.

 

yes its installed and its a tight fit, stays in place when you remove the bowl. I think it might be possessed.Oh one other thing I was checking the fuel screw pilot relationship and found it runs best at 3.5 turns out and will slow down idle at 2 out and die at 1.5 out like its lean on the pilot with a 62 pilot installed. Thats what I've always ran in my xr400's. The last one I had was a 02 and raced it in the B class hare scrambles and it worked fine.

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That's crazy. Have you had the fuel screw out to clean that passage and check its oring? Be sure its tip isn't broken off. Run a wire up thru that passage all the way into the carb throat.

You've haven't stated your elevation yet.

Does your WB exhaust use discs? If so, how many are installed?

http://www.4strokes.com/tech/exh_tune.pdf

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