Petrol smell in oil tank

[bobandbec]

On my A10 I seem to have a slight "petrolly" smell in the oil. Any thoughts on what might be the most likely cause(s). Carb, pistons ??
The taps are always shut off when not in use but I suppose there is still the petrol already in the carb/pipes. Looked at the float which seems to me working OK but haven't had the carb to bits yet.
Any advice would be very welcome.

Thanks

Peter

[bikerbob]

It is not unknown for petrol to leak into the oil, but it has to get past the the petrol taps and the float needle so I would be looking at both of these items urgently because if it is getting into the oil then there is a real danger that the oil is being washed off the bores. In the meantime I would try to elevate the front of the bike so that if petrol is leaking then it will run out of the carb bellmouth and not into the engine.

[Beezageezauk]

I'll go with bikerbob but would add that if the oil is contaminated too much with petrol the camshaft won't be efficiently lubricated and will suffer premature wear along with the cam followers.  This happened to me and I ended up with an expensive and time consuming complete engine stripdown.

Disconnect your fuel pipes and check that petrol isn't escaping through the taps when they are turned off.

Beezageezauk.
 

[muskrat]

G'day b&b. As above, tap/s & float needle & seat. Just fixed a Highly Dangerous with the same problem. Tap was leaking 1 drop every 15 seconds. I wondered where that gallon of fuel went!!!
 The only other way in is if the bore is glazed and rings aren't sealing causing blow by.
Cheers

[bobandbec]

Thanks to all for replies. Time to get busy.

Peter

[East_Coast_BSA]

I'll go with bikerbob but would add that if the oil is contaminated too much with petrol the camshaft won't be efficiently lubricated and will suffer premature wear along with the cam followers.  This happened to me and I ended up with an expensive and time consuming complete engine stripdown.

Disconnect your fuel pipes and check that petrol isn't escaping through the taps when they are turned off.

Beezageezauk.

When oil gets contaminated with fuel, it breaks down the oil film and ANYTHING and EVERYTHING is subject to damage.  And it doesn't take a lot of fuel to render the lubrication quality of oil to virtually nothing.

[The pirate]

If you run the petrol tank dry and leave the bike for a while the petrol tap cork seal will dry out and leak, they take a while to expand again once more fuel is added. This can be part of the above problem.

[bobandbec]

Thanks.
I've renewed the petrol tap pull/push part including the corks. They had a good soak to ensure they were "swollen" up before fitting, pretty tight to get in actually. Also cleaned out the float chamber and installed new float needle and the filter on top renewed. Only completed on Friday so will see how it goes now.
OH and yes drained and replaced the oil from sump, tank etc.
Thanks for suggestions.

[bsa-bill]

pretty tight to get in actually

Mine were the same and if you take more off so they slide in easy they leak again, I smeared them with a little grease and it worked a treat, will get washed off by the petrol no doubt but by that time they should bedded in

[East_Coast_BSA]

I "Steam" my corks over a boiling teapot.  Then I put a coating of bar soap over the cork (Irish Spring).  They fit good and snug.  I always leave some gas in the tank, I just add fuel stabilizer and isopropanol to keep the gas fresh over the winter.  Mine have been well-behaved for a few years now.  I know my father had trouble with them, but he would drain the tank every year.

[bsa-bill]

I always leave some gas in the tank

Yes mine dried out due having the tank off the bike for a good while and drained it before removel, previous to that the corks had been in 14 years without leaking ( wow is it that long since I first restored the bike)

[East_Coast_BSA]

I always leave some gas in the tank

Yes mine dried out due having the tank off the bike for a good while and drained it before removel, previous to that the corks had been in 14 years without leaking ( wow is it that long since I first restored the bike)

I always got the impression they didn't go for more than a few years without leaking.  14 years is a LONG time.  That's good to hear.

[Rocket Racer]

Not directly related but with methanol engines a phenomenon called bore washing is common, where methanol gets past the rings and contaminates the oil. As a result people running methanol dump all their engine oil after each race meeting to remove the contaminated oil.

Also brings to mind a mate from many years back whose morris marina's oil level went up  He couldn't understand why until it transpired the fuel pump (bolted to the block) was leaking into the motor. His engine was scrap but immaculately washed inside.

[nimrod650]

replace taps with lever and ball type they dont dry out