Fuel draining from tank into crankcase

[cornishman07]

Hi all,
I’m hoping someone can give me some guidance on my '95 fzr600r 4jh foxeye. Fuel is draining from the tank into the crankcase contaminating the oil. I’m confident it’s not the carbs as I’ve taken them off and cleaned them. The jets are clear, the floats are clean and free, and there is no gunk or debris anywhere.

It has an in-tank fuel pump and from what I’ve found out it’s a simple pump that fills the floats on starting and pumps the bottom third or so of the tank as this is below the carbs. Most of the time gravity gets fuel to the carbs.

There’s no petcock or fuel tap to turn the fuel off so I’m assuming something should close inside the pump when the ignition is off and it isn’t doing? then gravity is pulling fuel out of the tank through the carbs and down the cylinders, into the crankcase.
I don’t know if it’s the pump itself or whatever controls the pump (relay or something?) that’s not working, or how to test which scenario it is.

Any help with a diagnosis or replacement part numbers (or compatible parts as it’s a 22 year old bike!) would be greatly appreciated.
Regards
Richard

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I've just rebuilt my YZF750R fuel pump which is the same setup. All fuel must pass through the in tank pump, there is no second feed for gravity.

If fuel is getting into the crankcase with the ignition off and the bike parked up and not in transit, then it sounds like a float valve not seating correctly or not sealing.

I take it you hear the fuel pump start on ignition on then stop? I'm about to strip and rebuild the carbs on mine soon, so will look for how the float height turns the pump on and off.
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TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[Nobby the Bastard]

The only way fuel can get into the crank casing is via the carbs. Either the float height is wrong, the float(s) are punctured or the valve and/or seats in the carbs are worn.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[jimspeed]

It has to be either a float valve sticking allowing the fuel to siphon or the control relay for the pump sticking and letting the pump run with the engine off (if it has a relay).
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Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[temeluchus]

in a bike of that age the primary suspect is the float valve needle and seat. They are wear items that need periodic replacement.
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Some shite cruiser. Now with guns and FREEDOM!

[jaffa90]

Has it got a vacuum pipe next to the fuel tank outlet pipe?

[chris-red]

[MCN]

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[cornishman07]

Cheers for the fast responses everyone. I don't really know how a carb works or how to check one is working properly I've already had them off and apart once to clean them but that's all I did. Are there any guides you guys would recommend? If I type this into YouTube there are hundreds but I have no idea who's giving good advice and who just likes filming themselves!!

[skatefreak]

Had this on a cbr6 f3.
Float bowl seal do-hicky wasn't sealing...
Upon removing the carbs I was greeted with an inlet full of fuel
Carbs off, cleaned them and all was fine.

[cornishman07]

[temeluchus]

https://www.cyclepedia.com/manuals/online/free/fuel-system/float-valve/
Good info here. It's not a hard job and only needs very basic tools, just be aware you'll be dealing with fuel.

I'd also rebuild or replace the fuel tap as well, as a precaution, whilst you have it apart.

https://www.fowlersparts.co.uk/parts/4125589/fzr600-fzr600rg-genesis-3hhe-1995-010-b/carburetor-for-usa

Genuine part numbers here and you can find pattern parts with several vendors.
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Some shite cruiser. Now with guns and FREEDOM!

[jaffa90]

I'm not so confident now! They were clean at least! I'll read up on how they work and have another look.[/quote]
You no answer question!

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[stinkwheel]

As a 95 bike, it could well be ethanol in the fuel attacking your needle valves. I had a similar problem with a KLE500.

That kind of damage will look like white fur on the alloy of the needle valve and the end will look like it's been slighty nibbled. If this is the case, get some new viton tipped ones.

You can actually check if a duff needle valve/float is the problem too (but it is, can't be much else). It should be possible without removing the carbs from the bike. There will be a drain screw in each of your float bowls, when you loosen the screw, fuel will run out of a little spout in the bottom of the float bowl.

If you put a piece of clear hose on that little spout (other end open to air) then bend it up next to the carburettor body, when you open the drain screw, fuel will fill the hose to the same level it is sitting in the float bowl. In a normal carburettor, this will be slightly below the float bowl gasket. In one with a leaky needle valve, it will be the same as the level of fuel in the tank (ie, it'll piss out of the top of your bit of tube).

You could use this to test each carb, might only be one duff one.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[jaffa90]

[cornishman07]

I'll take the carbs off this weekend and check them properly this time. I feel like I know what to look for now.
I really do appreciate advice from those with the knowledge and are willing to take a minute to pass it on to someone they've never met! I'll let you know how I get on.

[jaffa90]

[Pete.]

[jaffa90]

[cornishman07]

[cornishman07]

[temeluchus]

[cornishman07]

A bit later than i expected but here are the pics