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throttle and goes off..

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hello all!first of all..sorry for my english!

i have a problem with my xr400r..when the petcock position is on and give a throttle it goes off!(the bike)

then i tried to put the petcock to position res. the bike it stays on also when i give throttle..as should be!i thougt it has to do with petrol or petcock or carb!any solution??sorry again for my english and hope you understand me! :)

thank you

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Before we dismiss the petcock as the problem, is your petcock vacuum operated, as in, has a separate vacuum line from the engine running to it?

Does the engine die immediately after switching from res to ON and giving it throttle? Can you repeatedly recreate that? Switch to res, throttle and engine does ok, switch to ON and bike dies with throttle, over and over?

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thank you for your reply!

the first thing that you say..it's ok!

 

the engine doesn't die immediately when swithcing to ON but sometimes works for some minutes when idle running and then died also without throttle..

when give throttle it everytime almost die..when i switching to RES its running ok as long time before!

 

 

 

 

Sorry again for my english man..hope you can understand me!

Edited by THunderweed

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You have to try to answer questions.

Does the petcock have a vacuum line running to it? Yes or no?

Be sure what you think is the ON position is really the ON position. If it really is the ON position, something is wrong internally with the petcock, blocking flow and the engine dies when the fuel level in the carb bowl gets too low.

What happens when you put the petcock to the OFF position? Does the engine die minutes after like it does when its in the ON position?

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yes it has..

and i'm sure that it's the ON position and yes when i put to the OFF its die after minutes!sometimes before i left the engine to close by this way..turn the petcock to OFF position so to goes off when the fuel level in the carb bowl gets too low!

i forgot to mention that when it starts to do it for first time it was after 2 weeks parked..and i try to put some fresh fuel and it was ok!with the petcock to the ON position..

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How is the quality of your fuel there in Greece?

Fuel in the US has a lot of Ethanol in it, so we have to be careful of letting fuel sit in the float bowl for long, because the fuel goes stale pretty quick. After 2 weeks sitting in the bowl its best to drain the and flush the bowl with fuel from the tank.

You might check your fuel for water contamination too. When the engine dies with the petcock set to the ON position, take the plug out of the bottom of the bowl and catch the fuel in a glass container. Water and fuel don't mix, so you'll be able to see water bubbles in the fuel if its contaminated.

Test the petcock. The petcock doesn't flow fuel until it gets a vacuum signal from a running engine. You know the res position seems to work ok, so set the petcock to res and run the engine to fill the float bowl. Kill the engine. Pull the fuel line off the carb, leave the other end connected to the petcock. Put the free end in a container to catch the fuel during the test. Make sure the vacuum line is still connected.

Since the carb bowl is still full of fuel, the engine will run long enough to do the test. Set the petcock to OFF position and start the engine. Turn the petcock to ON position and see if fuel flows from the free end of the fuel line. Yes or no?

If no, turn the petcock slightly away from ON in both directions to see if you can find a position close to ON where fuel does flow. If no, something is internally wrong with the petcock.

Then set it to Res position and check flow. Setting it to OFF should stop flow.

You can run the petcock in res position all the time, you just have to pay attention to fuel level in the tank, because you have no back up. When you're out, you're out.

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