four stroke engine help...actually a motorbike but I know you can help!

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firstascent2002

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Onmy transalp, after being laid up for about a year, then vigerous cvranking to start it I got a gush of fuel from the exhaust...

I found that the crank case was completely full of petrol so I have drained and changed this back to oil!. With new plugs the bike starts with the air box off. I am using a plastic bottle and a tube as a tank. When inverted, then fuel flows freely from this and with the bike idling soon enough fuel starts to appear from the the exhaust breather hole...

People have spoken of a petcock, I can't find reference to one in the haynes manual. If this was an outboard motor I would wonder if the float in the float bowl was stuck down...

If you were me what would you do next?

If I have to remove the carbs to inspect the float chambers, is there a spares kit avaliable in the UK for a carb re build for a 650 transalp xl ?!

Also, is there any way that having a restrictor kit might have precipitated this?!

Sorry if this is off topic, but engines are engines!

Jamie
 
Auto Petcock

Don't know about the transalp but on my Honda VTR, the petrol valve on the tank (petcock?) was automatic. a vacuum tube was connected to the carb and when the bike started the vacuum from the carb opened the tap. In theory if the bike crashed and the engine stopped, no fuel would flow out from the tank. This probably doesn't help you but if it failed and the float valve jammed open I would expect to see petrol everywhere, not neatly contained in the sump. Normally any petrol that makes it through to the exhaust is combusted as a backfire, fun in tunnels by flicking the engine kill switch off and then on, but I can't work out why you'd see petrol coming out the exhaust with it running. More details as you fiddle would be fun.
 
Stuck/sunk float, needle valve come adrift or a loose jet is my guess. Something pretty radical to allow that amount of flooding.
A petcock is merely a tap in the fuel line to shut off the flow when the engine is not in use. Not necessary unless you're leaving the fuel tank connected when its not being run.
No chance the "tank" is pressurised? Assume the "bottle" is vented?

The only thing it can be is a leak in the carb. I've had the same symptoms with a very loose jet too due to poor assembly so check all those too inc accelerator jet(s) and associated diaphragms if any.

Answer is certainly a carb strip, investigation and reassembly.
 
aslabend said:
the float valve jammed open I would expect to see petrol everywhere, not neatly contained in the sump.
Click to expand...
It seems the carbs are angled steeply downwards, so fuel could run into the inlet port and through an open inlet valve. However the carbs seem to be constant depression carbs so it would take some time for the fuel to flow past the needle in the jet. There again, it's had a year.
 
Nothing to do with the petcock - what you have is flooding and most likely caused by having the bike stand for a year. Modern petrol deposits gum when it evaporates and that gum will have stopped your carb floats from cutting off the petrol supply when the float chambers are full.

Take the carb(s) off the bike. Buy yourself a can of carb claener and then sit down with a nice clean working surface and strip the carbs. Easy enough to do. Clean every bit of them concentrating on jets and passageways. If you do this carefully, you may well not need any sort of spares kit.
 
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