TOPIC:

2016-08-06 Gas In Crankcase

This is a gas tank. A gas tank that doesn't vent all that well. That's why the cap is open now.


This is a 37 year old petcock. Above it is a full 5+ gallon gasoline tank sitting in a shop with 100F+ temperature. PV=NrT.


This is the hose that connects the crankcase to the air box. Crankcase vapors get sucked into the air box to make cleaner air for the state of Kali.


..and this is the result of a gasoline flooded crankcase. Note the evap rate has already lowered the level by an inch or so. About 1 gallon of oil. About 2.5 gallons of gas.


The old gurl wouldn't crank. Pulled sparking plugs. No fuel in top end. Huh?
Go change water. Find a lot of gas on the ground. WTFO? Mop up gas.
Drain float bowls.

What's that dear? You need help in the house? Ok, I'll help.

Return to shop. WTFO? Gas all over the ground.

The moment of realization. Remove air box cover and filter. Gas, about 1 inch up from filter bottom. Sick feeling. Did I kill this engine by spinning it and trying to start it? Thank goodness I did not use ether or something equally stupid to try and start her.

Oh, and the clutch lever now goes back to bar. What's up with that? Really bad feeling.

Drain oil. Remove filter and oil fill cap. Use compressed air to evap as much gas as possible.
Refill with oil. Used same filter, dried out. It was new just 10 minutes ago. Remove plugs again. Spin motor using starter to distribute oil to crank plain bearings and engine top end.

Not a good day.
Drain oil, replace filter, fill with new oil. Don't have any cheap oil, so Delo it is.

Start, she sounds a bit rough, but not horrible. No low end thumping from crank. Cams talks happily. Maybe I'm OK. Call it a night.
The clutch is still not happy. To bummed to call Ray and tell him I probably just destroyed his beautifully crafted engine. Fuck. Just F U C K.



Removed clutch cover. Check out how dry the friction disc is.


Disassembly pix for later install. No scarring. So far so good. But why no clutch lever?


Part of the disc is entirely dry. Could it be it was above the gasoline level?


Of course, by now, the bike is drenched in oil, my lift is a mess and you get the overall picture.


Soaked the plates in oil for > 24 hours.


Re-installed oiled up plates..
..and all is good! Clutch is back.

Could it be the cork based material needs oil to 'swell'?
Test ride proves all is good, clutch wise.

Telling a buddy at work today about it.. and the clutch lever going to bar for no good reason. His first statement "Did you flood the crankcase with gas? Happened on my Suzuki liter bike once."

Called Ray, he doesn't expect any damage to the engine. Something about how folks used to drain then fill crankcase with diesel for cleaning. That residual oil would still be in the filter and oil pump while I was spinning the engine to clear the top end. She did run, for maybe 5 seconds or 10 seconds max with combustion. And not all cylinders were firing. More like an occasional pop.

So there it is.

Ordered new OEM friction discs, just in case. Minimum spec, per FSM, is 3.2 mm. I measured each disc in 4 quadrants, my minimum was 3.45 mm so these discs are most likely OK. If so, then great, I just got a good deal for a fair price on consumable parts that might not be available in the future.

Also ordered a 12 Vdc fuel cut off valve.
Looking at a new Pingel petcock with adapter plate. I am not a purist.

..and got to look at why the tank does not vent well. This has been a problem since new.

So, there it is. I'm not going to pull the engine down to 'inspect'. I'll run her and see what happens.

Wish us luck.

I just did the Pingel tap and plate. A bit of a pain in the butt but I am very happy with it. If you go this route you'll have to grind the opening for the fuel tap to get the pingel to fit because its a round tap and the hole is somewhat rectangular. I emptied my tank, then filled it up with water so I could grind out the edge without blowing myself up.

Have you tried replacing the filler cap? There are cheap knockoffs on ebay but no one but you will know

Yes, I did replace the cap. From the great guy in Germany. So much better than the cheap knock off I bought

My KZ never did vent right, from OEM, day one.

Looks like I need to investigate.

Just another thing to do.

..and I'm thinking of an insane ride for this bike. This bitch needs a flogging, if you know what I mean...

dcarver220b,

Your fuel tank not venting correctly may be the main cause of the crankcase filling with gasoline. If pressure is high enough inside the tank, it can force the float needles off their seats. A combination of a leaking or open petcock and tank that is pressurized will fill the crankcase with gasoline.

If the tank vents properly, the float valve needles seat correctly, and the O-rings around the float valve body seal properly, gasoline will not flood the crankcase even if the petcock is leaking or open.

If you install an electric shut off valve or a manual valve that shuts off 100%, and the tank does not vent properly, the pressure inside the tank can cause the tank to bulge outward in places you do not want it to expand.

The factory fuel filler cap has an internal vent that exits via a spigot at the rear, underside of the cap. This spigot mates with a small pipe that runs inside the fuel tank and exits at the rear. A drain hose connects to the pipe. Possibilities for improper tank venting:

Fuel cap internal vent system not working. Does your replacement cap have the vent spigot at the rear? None of the cheap replacement caps on eBay have this vent spigot. They may not be vented at all.

Plugged up vent pipe inside tank.

Plugged up drain hose. I think the drain hose has a check valve in the line. Maybe it is stuck closed, or installed backwards.

You can see the top hole of the fuel tank vent pipe behind the main opening when you open the tank flap.

Get a 2 foot length of old throttle cable (without either end on) and carefully push it into the top hole and work it through the pipe. It SHOULD exit at the piece of pipe sticking out of the tank at the rear right hand side.

If the cable will NOT go all the way through, then it is likely to be blocked. If it is blocked then you need to carefully pour some petrol down the pipe itself to loosen the blockage and keep pushing the cable in until it clears.

Once clear, get a 100psi line into it and blast it clear fully.

This will then allow the tank to release pressure when the flap is closed.

Pete F
UK

Great responses, Thank You.

I'll get after it again when the weekend rolls around. Still a working stiff..