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XR400 dies after few seconds of starting

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SOLVED: Please read all the thread :bonk:

Hello community - Let me start by saying that this is my first post, and it is a pleasure joining this community and I hope to be an active member.

A couple of weeks ago I purchased a 1998 XR400 for dual sports purposes (commuting, trailing, riding with friends, etc) and had real blast with it. However yesterday morning (after a night of rain and cold weather) it has been giving me a bit of trouble to start/run it properly...

After I manage to cold-start the bike (with higher idle + 1/2 choke) and I leave it started to warm a bit, the bike shuts down after around 50 seconds. Then I restart it again, and this time, it dies after 10 seconds or less.

This morning I did the same procedure - and again, after starting successfully, I left it with the high idle, and then after 60 seconds or so, dies again immediately.

What could the problem be? Someone at work suggested to spray some WD40 on the high tension and will probably try that as I get back home. Do you think it can be a serious problem? I really want to solve this by myself without getting it to a local mechanic as they are expensive here where I live.

Thanks,

XRH400

Edited by xrh400
Marked as solved

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Could be a fuel blockage or water in your fuel...

I would remove the tank and drain it completely...If you do this into a dry/clean container you can see if any water was in there..

Check that fuel is flowing out of your petcock ok....

Remove the carb , jets and give it a good clean out...compressed air will be useful....

Replace the pilot jet...

Put it back together , and pour in some fresh fuel.....

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So the bike was parked outside in the rain?

I'm assuming you XRH has the same carb as our US model. Take the plug out of the bottom of the carb float bowl, draining it. Then open the tank petcock for a second to flush it. Then put the plug back in. Fuel on, try starting again.

You really need to spend some time getting to know your carb if you're ever going to get it to run right and reliable.

When the temperatures drop, the air becomes more dense, leaning out the air/fuel mix the carb is currently jetted for.

You need to find out how many turns out, from seated, your fuel screw is set and what jet sizes your carb currently has.

Spend some time with the bike to keep it going while warming up. After it's warmed up and will continue to idle on its own, you need to tune the fuel screw to its highest effect on idle speed and best throttle response off idle. It's the fuel screw setting that determines how well a bike starts and runs at idle, so it's important that you do this.

Armed with these jetting and fuel screw setting figures, tell us what you find and then we all can make a more informed decision on what you need to do.

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thanks all for your replies guys.

I only had a few minutes to spare to fiddle with the bike - hopefully tomorrow I'll have more free time to dedicate.

Till now I did the following:

1) sprayed some wd40 on the high tension - started the bike but then again, after some 50 seconds, it stalls

2) I removed the fuel line and checked the fuel cock if it works ok in all position - and i can confirm that it is working well

3) I removed the tank and drained it completely into a container - can someone tell me how do i determine if it has water?

4) I tried to start again the bike (with the assumption that the carb has still some fuel) - guess what? it starts and takes the SAME AMOUNT OF TIME before it stalls.

Something is not right here...

Any tips before I start disassembling the carb tomorrow?

PS: I guess my XR400 is a Japanese import model

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This morning I removed the carb and disassembled it - Carb is Keihin and jets are 155/55. Carb was dirty and jets are too small to say if they were clogged or not, but I used a Carb cleaner and cleaned everything.

Tomorrow I reassemble everything and see if it works...

PS: I did not find any water in the container where I drained the gas.

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fuel delivery issue, as stated before check vent tube on the fuel tank. If it's creating a vacuum because it's plugged it will not deliver sufficient fuel to keep the bike running.

i forgot to mention that i still have the problem with the fuel cap removed (i guess that eliminates the vent tube possibility at all)...anyways tomorrow morning i'll assemble the carb

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hello fellows I solved the problem! Read whole post, cos I don't think it was the carb after all.

After I reassembled the carb and filled the tank with some gas, I still could not start the bike easily. Then after some 30 kicks, it started....And then it died after some 50 seconds. F*** AGAIN!!!

But since I had all the bike stripped down, I could hear the mechanics more properly and something told me (sputtering from the carb) and some light backfires, that the cause may be a fuel starvation.

There were no leaks from the fuel line. But could it be the petcock??? I could swear I drained the tank from it...So I turned the petcock to the RESERVOIR position, and it started with the first kick and DID NOT DIE on me!

So I guess I have something in the petcock when it is in the ON position - I did not have time to further troubleshoot so I ask you guys for another opinion on this.

Mind you, I am super happy that the bike started even after I reassembled the carb (first time for me!) - I am not pissed off that I removed the carb for nothing cos I still think it needed a good cleanup - the idling is so much sweeter right now, and the throttle snap just adds that nice grunt.

So guys, in summary (before I experiment with it some other day), could it be that the petcock is just screwing around just in the ON position?

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So guys, in summary (before I experiment with it some other day), could it be that the petcock is just screwing around just in the ON position?

It's possible. Just doesn't happen often enough to make one consider it while troubleshooting. Maybe you're on to something.

Connect a long piece of hose to the petcock, run it into a container and compare flow rates between ON and Reserve. Slowly turn the petcock away to either side from ON to see if there's a "sweet spot" that makes it flow better.

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What about debris in the tank that settles over the petcock while on (vibrating and flowing) but not while sitting???

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I had the same issue with my bike and it turned out to be the petcock valve on the tank.

On was not working but reserve was....

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