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Fuelling issue


Mickly
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Mate of mine has just brought an XF650 Freewind and has discovered that if he leaves the fuel tap on it fill the crankcases with fuel.

He’s checked the float heights and that the float valves are clean and seating correctly.


Can any of our resident technical whizz’s suggest what else it might be?


Thanks

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Looking online it looks like an o ring seal on the needle valve body to carb, are they ok?

You could take the carb tops off and remove the slide and diaphragm, hook it back up to the tank and see which carb overflows ?

Punctured or porous float?

Cracked carb body?

Total long shot but modern unleaded not doing something to the 20 year old plastic floats?

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What everyone has said. The usual cause of non closing float valves is particles of dirt that lurk behind the valve seats . This means that when you remove the carbs and invert them it can travel back down the link pipe . You can replace the needles or even the seats if you like but as soon as you refit and turn on the fuel the dirt comes back again and the valves stick open . So a thorough flush out with carb cleaner squirted through the valves backwards down the system should do the trick. followed immediately by fitting a nice big paper type fuel filter . As for the tap , that needs a proper service . Look for a microscopic hole in the plate between the two diaphragms . If that's blocked , there's the culprit . Good luck. By the way , you might want to consider modifying the crankcase breather hose so that this doesn't happen again . Just make it longer inside the airbox.

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Thank you all for your considered contributions - I’ll pass them on and let you know what transpires, although this may be some time knowing how he goes about things.

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One other thing to check is if he is actually leaving the fuel tap on 'prime' and not 'on' as this will cause the same issue

 

Very true but this still indicates an open float valve .

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Mate of mine has just brought an XF650 Freewind and has discovered that if he leaves the fuel tap on it fill the crankcases with fuel.

He’s checked the float heights and that the float valves are clean and seating correctly.


Can any of our resident technical whizz’s suggest what else it might be?


Thanks

 

does it have a vacuum fed tap ...

the diaphragm in these fail and keep fueling

can hydrolock engine


gtr1000 renowned for this

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One other thing to check is if he is actually leaving the fuel tap on 'prime' and not 'on' as this will cause the same issue

 

Very true but this still indicates an open float valve .

Ah but not if it was coming via the Fuel Tanks Vacuum pipe :wink:

 

Oh , I see , you think it may have been connected up wrong . Yes that's possible but it would be on the wrong side of the diaphragm wouldn't it ?

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Mate of mine has just brought an XF650 Freewind and has discovered that if he leaves the fuel tap on it fill the crankcases with fuel.

He’s checked the float heights and that the float valves are clean and seating correctly.


Can any of our resident technical whizz’s suggest what else it might be?


Thanks

 

does it have a vacuum fed tap ...

the diaphragm in these fail and keep fueling

can hydrolock engine


gtr1000 renowned for this

 

ER5s do it , particularly on remote campsites hundreds of miles from home !

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No its not been connected up wrong, what I'm saying is the Diaphragm is bugger

 

Ok so if the fuel doesn't shut off it's still got to get past at least one of the float valves .

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I’ve just found out that he’s replaced the vacuum fuel tap with an on / off / reserve jobbie

So no fuel going down the vac pipe.

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I’ve just found out that he’s replaced the vacuum fuel tap with an on / off / reserve jobbie

So no fuel going down the vac pipe.

 

Right, good , so he must have left it on and fuel must have got through one or more of the float valves . So back to my original post where I suggested he flush out the dirt or possibly replace the float valves .

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