CB750 Fuel Leak

[manasotaman]

I bought my 1980 CB750C F2 in the USA, and it has been off the road for a couple of years. I just tried to start it.
It fired up okay, then a large amount of oily fuel gushed out of the plastic tube under the battery box. What is going on here? I don't think it's a stuck float, the overflow there are four black tubes. The tube is obviously there for the purpose of offloading this fuel.

Also, there is a small trickle coming from the gear selector on the gearbox.

[fraggie]

[Fizzer Thou]

It sounds as though the floats have stuck open and allowed the entire fuel tank to flow into the engine.
I had this recently on a dirt bike where the owner had left the fuel tap in the 'ON' position and has now FUBARed the engine.

If the oil has a distinct petrol smell to it,drain the oil,change the oil filter,check the float valves work correctly and check that the air filter is not soaked by petrol/oil that has blown by into the air box via the crankcase breather.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[HD]

[Fizzer Thou]

The Yam WR250F that i was working on has ruined bores as the petrol leaked from the tank into the carb into the open inlet valves past the piston rings and into the sump - over a period of over 12 months.A compression check showed up as 60psi which increased to 80psi with a squirt of oil down the plug hole.The compression should be somewher in the region of 200psi,so the engine needs a top end overhaul as the piston rings are stuck in the ring lands and losing a severe amount of compression.The engine starts but has no power and quickly causes crankcase pressure problems.

In the case of the Honda 750 which is the subject of the thread,I would perform a compression test in the first instance.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[MickC]