Trans oil in Cylinder? Help! (1982 PE250 ...)

[Hardo]

Hey guys..
Okay... I have rebuilt a nice 1982 PE250 Z. It has a very weird issue now though that really has me puzzled.

After I rebuilt it, it was running fine, then all of a sudden there was a lot of oil seeping from the exhaust header area, and kept wetting the plug. Through my investigations, I figured it had maybe blown a right hand main seal and was sucking trans oil into the crank.

I pulled the top down again, and sure enough the entire crank, piston and cylinder were wet from dark oil that smelled like heated trans oil. Okay, no problem - I will buy a right hand main seal and shaft o-ring.
Those two items were replaced, then engine rebuilt and thrown back in...

Bike would then fire for about a second or 2, then stop. Oh nooo.... what was it now....

Okay, pulled the exhaust off, and no way.... thick oil there again....  engine then pulled out for the THIRD time...


I have it now pulled down. I am not really sure where the oil could be being drawn from into the crankcase? Anyonw have any ideas on this or have experienced it themselves?

The only thing I can think of is maybe the centre crankcase gasket... maybe oil is seeping through it into the crank area??? Could this happen? I think I should replace it just in case.

These are great old bikes, but this one has me a little stumped.

Any PE exPErts out there? Your thoughts would be appreciated!!

Help..... *going crazy here!!*
Hardo.

[oldyzman]

Mate i'm not 100 familiar with th PE, you may be right re the centre seal, but also consider the main bearing on the clutch side of the motor has a main seal which stops the gaerbox oil from enterng the crankcase...
Cheers Brett

[Hardo]

Thanks Brett. Yes it was the Clutch side (Right side) Main seal I replaced the other day..... and the o-ring on the shaft.

I really do suspect it's the centre case gasket. I have just NEVER come across that issue before.. Has anyone? 

When I think back.... the engine had a gut full of water when I got it... hmmmm... maybe that had deteriorated the gasket enough....  ?

-Hardo

[monaro308]

In my karting days i made up blanking plates for the exh-port and inlet port with a bung on it to fit a rubber tube with a low pressure guage and one of those medical bulb things to take your blood pressure.
It was great for diagnosing seal leaks/crankcase leaks like yours.
Apart from the main seal and the o ring which we assume is in the order of bearing,seal,oring,spacer,primary gear,all of which you have done,all i can think of is a crappy centre gasket or a porous/cracked casing.

[Mike52]

All twostrokes are the same from whipper snipper to Pe .
If a chainsaw blows the c/case gasket then it sucks chain oil , a victa sucks air ,and runs lean, and so on.
The bottom end has to be sealed or the problems crop up.
Have seen this type of thing heaps of times, used to work at Victa.
If you suspect a leaking seal and can get at it then lay the engine on it,s side and put a bit of t/stroke fuel on the seal and turn the motor over.
The fuel will either bubble or disappear if you have a leak.

[PEZBerq]

It isnt too difficult to do a pressure test on the engine. I do it after every engine rebuild.

Blank off the intake and exhaust using a 5mm steel plate with a rubber gasket of some sort (I use toilet cistern rubber flap valves from Bunnings and cut them down) Drill and tap each seal plate for fittings for a pressure gauge and a valve off some fork air caps. Apply about 5 psi or so of air and see if the pressure holds for 1 minute. If it does then all is good. If not then you have a leak - could be the sealing plates though so need to check that first before assuming it is the motor.  Soapy water and a small paintbrush can be used to find where the air is bubbling out.  If center gasket is leaking then it will pressurise the gearbox so plug the vent (if it has one) to check for this.  If in doubt pull it down and use liquid gasket sealant together with the paper gasket - I use Threebond grey or black with good results. Dont forget to let the sealant cure before doing an air test  .....been there!  Good luck

[Hoony]

all excellent advice above, picked up a bit myself.

were the crankcases in good condition when you inspected them or did they have some damage on the mating surfaces?
any corrosion inside when they were pulled apart?
are all the bearing / seal housings ok?

run a straight edge over each case half when you dismantle again and as above use some jointing compound when assembling       

[Lozza]

If the seal and o-ring are good check for the case leak(check for any welds) I would also give the the crank a spin between centres and make certain that end has no run out.

[jimg1au]

this is the easist way to check burning gearbox oil.
step 1 drain oil
step 2 put castrol r30 in your transmission
step 3 start bike if you can smell the r30 burning and you have replaced clutch side seal and oring stop bike stip and rebuild
if you cant smell r30 burning your crank is full of 2t oil and needs to be burnt out and your carby retuned
hope this helps
jim

[LWC82PE]

Im surprised you came all that way and didnt replace the gasket. I like to use Threebond aswell for additional insurance.. Make sure you have put the oil seal in the correct way too.

[brent j]

Make sure you have put the oil seal in the correct way too.

I've seen manuals that show the seal fitted both ways. Generally an oil seal is designed to work one way, ie hold pressure in one direction.

On a four stroke it's easy, it's there to hold the oil in the crankcase so the open side of the seal, with the spring, goes to the inside.

On a two stroke I've seen manuals for the same bike show the seal fitted both ways. Now on a two stroke there is alternating pressure in the crankcase (positive then negative then pos......)
Since a two stroke tends to suck gear oil into the crankcase then I'd say the seal should be fitted with the open side facing the gearbox, unless you have a double sided seal.

What say you all? Lozza?

Brent

[lukeb1961]

I assume you replaced all the engine seals and O-rings already.
did you bother to file the centres of each case flat?
With age some of them develop an interesting bow. You DID replace the centre gasket and use lots of quality sealer?
I always run around the case bolts in order to make sure they have nipped up properly.
Also, have you (since running) gone over them all again?
Including the head :-)
It is sometimes a huge surprise how quickly things bed and loosen.

Luke

[Hardo]

Thanks for all the responses guys. 

I didn't split the cases originally, but am most certainly doing so this time... will get a new centre gasket and fit it with good ole Threebond.

I will check the deck levels once they are apart and cleaned up, so thanks for that tip.

Thanks Brent... now you have me wondering.... which way should the Main seals be fitted?? I have them installed with the "open" part (the spring end) toward the crank... on both sides...
I'm an Aircraft Engineer, and certainly understand hydraulics and how seals work, so this would make best sense (which brings me back to wondering if the Japs were on the same thought processes...lol) .... any pics or thoughts on that guys?

In any case... this PE250Z will fire again....
Here is a pic prior to teardown #3 ... 

[DR]

Never used 3Bond or any gasket goop on any Suzuki crankcases and never have they leaked. They didn't use it at the factory so unless there is a definate surface problem I wouldn't use it in this instance either. Just a smear of fresh oil both sides of the gasky then install it

[Bikeaholic]

I had a similar thing happen with my RM250X. Wasn't until I split the cases that I found that the steel inserts in the cases that the main bearings fit in had come loose and oil was getting sucked past them. Apparently a common problem. I imagine the PE's would have a similar setup. Thought it was the seals or centre case gasket myself until I worked it out. It was drawing a vacuum via the gearbox breather hose. Also blowing heaps of smoke, running like a dog and fouling plugs. Worth a look while you have it apart