Petrol tank emptied into oil sump

Hi All,

Some of you might have been following my thread on the Ireland SV section;
http://forums.sv650.org/showthread.php?t=130385

but basically my SV650 2000 engine blew up. It started as a metal ticking, turned quickly into a loss of power and then sounded like 1000 spanners falling down metal stairs!

So I decided to drain the oil to look for metal bits, as recommended by a few people. What I found shocked me and I would like some opinions please.

I found no metal deposits at all, but the oil came out with some force, followed by petrol. The petrol tank had about 3-4 litres left in it when the engine blew but is now completely empty.

Is assume that the piston and input valve (front cylinder I think) are smashed and that petrol could freely flow out of the tank (does this not require a vacuum to suck it down the pipe??) through the carbs, into the inpput valve hole, past the piston seals (if the piston is still in one piece) and straight into the oil sump. Could this happen? Is it likely that the piston and valve are done or just the piston?

FYI, when I drained the oil it normally holds max 3 litres; I drained 6 litres out of the sump plug!!!.

Opinions welcome!!!!!!

Phil

Phil,

This sound like a combination of at least two things (assuming curvy):

1. Faulty fuel cutoff valve allowing fuel to flow without engine vacuum.
2. Sticking float valve / incorrect float height allowing fuel to continue to flow after the float bowls have been filled.

This caused the fuel to overflow from the carbs, down into the cylinders and eventually into the sump past the piston rings.

The petrol in the oil has thinned it out to the point where the engine bearings are no longer lubricated effectively causing metal on metal contact.

I would imagine the big end bearings and crank are knackered, followed by any other bearing surfaces depending on how long the engine was run for.

[fizzwheel]

My SV did that, The fuel Tap was knackered and was still letting fuel flow through when the engine was off.

I suspect your problem was caused by the same thing.

Maybe you can see if you can slot in a fuel injected engine from a K4 SV. Fuel injected motor, curvy styling...best of both worlds!

Sorry to hear about the mechanical faliure though. If you start pulling the engine part to investigate further, would you mind taking pictures as you go along and posting them on here? they can be quite educational

[fizzwheel]

How I found out it was my fuel tap was by pulling this pipe off the bike



which then the fuel started running out of..

I was lucky I put my bike away one night and tried to start it the next morning and it wouldnt start for ages and when it did it started blowing blue smoke out the exhaust where the petrol had thinned the oil so I didnt ride it, which I think saved the engine, it did take me ages to track down the faulty fuel tap though.

Might be worth popping the lid off your airbox and having a look at it, mine was fuel of petrol, I had a full tank so it filled the sump and then backed up into the airbox, was a right mess...

Thanks for your input guys. I have planned to replace the engine and would have been raging if the same thing happened again. I assumed it was just that the engine was trashed, never though that a dodgy petrol tap/filter would thin the oil and cause failure that way!!

I will put some petrol into the engine tonight and watch where it goes!!!

Cheers,

Phil

[yorkie_chris]

The thing on the right of the pic by fizz is not the fuel tap it is the fuel pump.

Fuel tap is vacuum operated and on the bottom of the tank, a fault here could dump petrol straight into the inlet manifold.