A little bit of fuel in the oil

[Darwin_R65]

Hi all,

Haven't been to the forum for a while,

I also haven't ridden my bike since before Christmas.
The monsoonal rains here in Darwin haven't encouraged riding.

It ran out of rego 2 weeks ago and today i thought i'd better take it for a roadworthy and renew the rego.

I didn't get out of the driveway.

It started first kick, but only ran for about 30 seconds and stopped.
This happened each time i started it, and then I noticed fuel pouring down the back of the gearbox.

HUH?

Where's that coming from....

I went to the local REPCO shop and bought some new fuel hose to replace the one that runs between the carbies, but it looked fine. Wet with fuel, but i couldn't see where it was leaking.

Scratching my head, and to distract myself I pulled the oil dipstick and there was no oil level. hmmm not good.
Then I thought I saw a wet mark about 4 inches above max, but it wasn't an oil mark.
I dipped it 2 times more to be sure.
Then i tried it only half in, just to be sure i wasn't rubbing it against something. There was the wet level, but it didn't look like oil

I smelt it and it smelt like fuel.

I looked at where the fuel hoses ran and thought how could fuel get into the sump, and why was fuel pouring down the back of the gearbox when it was running?

I removed the air filter and removed the airbox.
Underneath was fuel.

I"m guessing that my carburettor needle has not seated (I have a bad habit of not turning fuel off) and allowed fuel to drain into my cylinder head, which has leaked through a very worn valve guide and into the sump.

When i started the engine, the mostly fuel mix in the lubrication system    
has pumped around and pushed out the vent at the top that feeds into the air filter and run out the drain which feeds down the back of the gearbox.

I guess I'm lucky the bike ran and didn't backfire, igniting said fuel.

Looks like I'm due for some major servicing.

regards

John

[nhmaf]

Under NO conditions should you start the engine again til this is all sorted!     Indeed, your diagnosis of draining your fuel tank into your engine is correct.   I'd be sure to check your petcock to make sure it does indeed shut off and that it wasn't a failure there, rather than your own forgetting to turn it off.

You might be lucky if things didn't run long enough to incur damage without proper lubrication.  But, you were already lucky, it seems, to have not had one cylinder still full of fuel at the outset, which would likely have bent a rod and ruined that cylinder.  So, "maybe" you will get a free pass this time, and just go through with draining the oil (I'd probably pull the sump cover and inspect inside for signs of worse issues) and replacing the filter.   Some would recommend that you pull things apart to inspect the crank journals and big end bearings, but from what you've described, you might have dodged the bullet -- I'll cross my fingers for you.

You do want to also check that float needles' sealing and stopping the gas flow in both carbs, but as the Bing people say "our carbs are not petcocks" and you do need to post yourself a note to make sure you turn off the petcock(s) every time you are leaving the bike parked for a while.

Good luck, John!

[steve hawkins]

I did the same thing years ago, when I left my fuel cock on for 2 month over winter.  Ran for about 30+ seconds, rode it up the street even, until the fuel/oil started coming out of the breather.  Stopped the bike.  realised what had happened.

I drained the oil/petrol, refilled with oil, new filter and jobs a good'n.

Never had a problem after.

Never left my fuel cock on after though.

Fuel gets passed the rings and goes into the engine.

The fact that it started, sort of indicates that you should have got away with hydraulic lock on your engine.

[steve hawkins]

C O C K = T A P

[Luca]

Since you were pushing fuel into the airbox, you might also want to check the oil in your transmission just in case it got past the bolt in the bottom of the airbox.  Not likely, but it doesn't hurt to check.  If you do find fuel, I'd then check the driveshaft tube and final drive.

I'm curious how much fuel the overflow pipes can let out of the Bings.  I'd think if you were flooding that bad you should also have fuel coming out of the bottoms of the carbs.  Make sure the little overflow pipes in the carbs are clear while you're at it.

[livingdeadhead]

when i picked mine up 18 months ago the sump was full of fuel too, yea it had been left on , drained it , left it for a few days for the residue to evaporate, filled with cheap oil , ran up to temp , dropped oil , changed oil and filter , i'm FANATICAL about checking the tap now, mind you ive had it on jap bikes too .

[Barry]

Like Luca I thought the carb bowls should overflow on to the floor before filling the cylinders with fuel. Isn't that one reason why the Bing  independent float kits are badly thought of because the replacement bowls have no overflow pipe.

If I had a sump fuel of fuel I would want to know why the carb overflows didn't work.  Maybe the over flow tubes should be shortened a little to make them work.  I always turn the fuel off too but everyone is going to slip up eventually. I think I forgot on one or two occasions in 7 years and got lucky.

[livingdeadhead]

ideas for a vacuum fuel tap anyone?

[nhmaf]

I think that it is possible for the fuel flow from the tank to exceed that of the overflow tube (provided that your carbs still have them), and maybe if the tube is not fully clear, it may flow even less.   I think that the level of the top of the tube is high enough that fuel can still run down the downward angled intake and into the cylinder if the fuel level is just slightly above it, and that path is of less "resistance" than the tiny diameter overflow tube.

As to vacuum-operated petcocks - it is interesting to see how things are viewed from the other side of the fence.   One of my other motorcycles is a Kawasaki Concours (GTR 1000 for you folks in Europe).  This bike is possibly even more bulletproof than any BMW made, but one of the infamous weaknesses that everyone lives in fear of on it is.... the vacuum operated petcock.    The bike has a manual fuel tap, but it has NO "OFF" position, merely "ON", "RESERVE", and "PRIME" which allows fuel to flow even without a vacuum pulling it so you can fill your carbs and start the bike after the bowls have been drained.    A number of people (not a large number, but more than a few) have suffered from a failure of the vacuum part of the petcock while the bike was parked long term, and subsequently ruined an engine by starting it up with one or more hydro-locked cylinders full of gas.   It is enough of a fear that there are several after market kits are available to convert the vacuum petcock back to a fully manual one, or another kit which uses and electrically driven solenoid valve that has to be powered on with the ignition key to allow fuel to flow to the carbs.

I guess the moral to the story is - always be aware of your petcock operational status and position, and be sure to check your engine/oil sump for telltale traces of gasoline before starting up your bike after it has been sitting for a period of time.

[livingdeadhead]

if its going to sit for some time i'd drain the fuel , it goes off and the additives attack the alloy in our old iron , old brit bikes carbs are prone to it too , or so i'm told ...

[Luca]

I had a Kawasaki vacuum tap on a Vulcan 750.  The Prime feature is a bonus... they eventually got rid of it and you'd have to crank the engine to get the fuel down to the bowls.

Vacuum petcocks are more expensive, so are the rebuild kits, and they provide more modes of failure than a simple manual petcock.  The "on" position is "off" without a vacuum.  Usually it is a spring loaded piston with a diaphragm that is drawn back by vacuum to open the fuel passage(s).  If you're worried about failure you can put an in-line valve in but then you're back to a manual petcock.

You have all the potential for the petcock to fail and continue flowing fuel to the carbs, but the added potential for the diaphragm to fail and cause fuel starvation.

Like a lot of things on our airheads, I've found the simple fuel tap to be plenty effective and pleasantly simple.

[livingdeadhead]

mind you its just a 'memory' thing , not a problem with the bike at all , finding a scapegoat for our own shortcomings! lol