GPZ 550 Unitrak 1982 fuel leak in to oil

Hello.
I have an 1982 GPZ 550 Unitrak. I've noticed that my (new) oil is contaminated with fuel after some time of non-use and occasional start.
Petcock is bad and I've modified it to ON/OFF. Vacuum membrane does not work so I've expeled the option. I've replaced it with solenoid valve.
Prime is ON, ON is OFF. Tested it and it works like I've intended to.
I did "clear tube check". 2,3 and 4 were ok. Float level was approx 3 mm below the bowl line. On the other hand, 1. was AT the bowl line.
So, I've stripped down my carbs and have them on the bench now.
When I flip them upside down and blow air in to the fuel intake hose, nothing passes. I mean, NOTHING! Air tight.
All of the floats stand at the same level.
So, ???
Where did the fuel pass into the oil pan and how? Any ideas?

While it may seem that your float valves are sealing, over time they can dribble and eventually the carbs will overflow. Prior to 1981 most carbs had an overflow control feature where excess fuel drained out a nipple on the bottom of the float bowl but that went away for emissions reasons. After that when the carbs overflowed it would fill up the airbox and flow into the engine through the intake port and then into the combustion chamber, where the fuel leaked past the rings and into the crankcase.

The fuel can only get in the oil if the floats are leaking or intermittently leaking. Now that the TK carbs are back together, try a more basic leak test. Put the carbs on your bench in the upright position. Attach a gravity fed fuel source to the carbs. I use a PJ1 fork oil bottle with the bottom cut off. Attach a fuel line between the bottle and the carbs. Fill it with gas making sure it will not spill. Come back in the morning and see if you have gas weeping out of the carbs. That will verify the condition of the float needles and more importantly the springs.

Below you can see the float bowls from a 1980 (with overflow tube) and 1981 (without the tube) CV34 Keihin. The 1981 bowl doesn't have the tube (although the pilot hole is there, but it's not drilled through.)

P1020761 by nessism , on Flickr

Thak you. I've already did something like that.
I've maid an IV from the beer bottle and lamp stand.
Although didn't use it yet. I'll test it tomorrow.

Using an IV stand is fine, just make sure your fuel reservoir is vented otherwise fuel won't flow freely. A beer bottle sounds cool but unless you drill a hole in the bottom to vent it won't work.

Sorry. No attachment! Here it is. Carbs are on the bench now. With IV stand next to them. I'll keep you posted for results.

So, I've tested my carbs on the bench with homemade IV for float leaks, did the clear tube test for float levels and used a compressed air can for diaphragm test.
Results are:
1. IV - not a sigle drop of fuel goes trough the carbs to the engine. I've left it set for 24 hours and - nothing. I've even closed top vent on IV and and squeezed for pressure check. Nothing gets trough. Floats are sealed tight.
2. Clear tube test - levels on all 4 carbs are just below the float pan screw tip. That would be about 4 mm below the float pan seal. The manual states that it should be between 3 and 5. I guess that's ok too.
3. Diaphragm test - after disassemble and resemble they sound ok (by ear, whoosh, whoosh) and they lift with compressed air can check. I guess that's ok to.

So, how does the fuel end up in a oil pan?
I'm guessing that one of the float needles was stuck and than when I've removed the carbs and turned them upside down the gravity of the floats brought the needle to life.
Should I put them back on again or there is another check that I've missed?

Any debris in the tank? Even a small flake of rust can get under a float needle and hold it off the seat thus leading to leakage and overflow. Some people use filters to protect from such things, just be very careful to select your filter carefully and make sure it's designed for a gravity feed fuel system. Paper filters for pressurized fuel systems won't work, although they filter better that a mesh filter.

Another thing to check is your petcock. If there is internal leakage there may be fluid leakage down the vacuum line and into the carbs that way.

You have bypassed the vacuum petcock, got rid of the vacuum membrane with the O-ring. You have also confirmed the petcock in Off position there is no gas dripping overnight, correct. BTW the O-ring & spring is what seals and the repairs kits contains all the parts and are cheap too.

Back to carbs on the bench with the homemade IV for float leaks. Give the carbs which are full of gas a couple of quick shakes up and down. That might get the carbs leaking.

Nessism wrote: Any debris in the tank? Even a small flake of rust can get under a float needle and hold it off the seat thus leading to leakage and overflow. Some people use filters to protect from such things, just be very careful to select your filter carefully and make sure it's designed for a gravity feed fuel system. Paper filters for pressurized fuel systems won't work, although they filter better that a mesh filter.

Another thing to check is your petcock. If there is internal leakage there may be fluid leakage down the vacuum line and into the carbs that way.

Thank You.
Petcock was long gone.
It was leaking even after I've rebuilded it with the new set. The needle just wouldn't sit right. So, I've modified it to ON/OFF (PRI is ON and ON is OFF). No leaks on OFF.
Vacuum hose is gone and ports are sealed on both ends.
Also, I will install electro magnetic fuel valve before I put the carbs back on.
Even modified, petcock still have its own filter. I've left it on.

Due to the fact that all checks cleared, I've decided to put them back on.
There were pods on instead of an air box. I have an original air box sitting around.
I know it's a wrestling match to put that all together but that will be another topic.
Thank you again!

EDIT: IV wasn't high enough. Luckily I din't put the carbs back on. IV was well above the carbs but not high enough.
So, 3-rd carb is leaping fuel. I've switched float needle from 3 to 4 and now it's the 4 that is leaking. 3. is dry. Definitely, the float valve needle is the issue.
On gravity, it is shutting down fuel flow, but on buoyancy it does not. (It's not the floaters issue - I've switched the position from 3 to 4).
I've noticed that that needle's spring is stiffer than the other ones.
Is there anything I can do or do I have to order a new one.