1997 900ss oil leak

HI ALL

I Have a stubborn oil leak coming from the vertical cylinder and is also fouling the plug. I have tried to seal the o rings with threebond but its still leaking but not as much as before. i just need some assistance in diagnosing the leak. my thoughts were the oil dowel because when i first changed the o rings i noticed bubbling around there but now im not so sure.

i have attached some photos. do you think i could get such a leak from worn piston rings.

I'm not familiar with this particular engine, but an engine is an engine right lol. Based on the carbon build up on the piston I would suspect your valve seals and valve guides are done for, particularly the exhaust valve as that's where the most build up on the piston is. I don't think rings would cause this unless they're massively worn. Was there much blowby coming out the crankcase, or fuel dilution in the oil? That would be a sign your rings and or cylinder are shot. The oil dowel leaking would only be external to the engine as it would have to get passed the head gasket to enter the cylinder. Hope this helps! Also if it is your valve seals that are leaking by its most likely leaking the most while the engine is off, is there noticeable smoke from the exhaust at start up? Again good luck with your diagnosis!

ive already changed the valve seals and check them when the heads were off so i dont think its that. ive had a valve seal fail before and it clogs it up pretty quick. also there is no smoke whatsoever. the bike runs really well other than this odd leak.

how do i detect blowby? also this doesnt have a head gasket it has a set of o rings.

if you take a look at the pics you can see carbon on the rim next to the stud and also oil around the rim.

i was also told by my mechanic as you have stated that oil couldnt get through to the piston from the oil dowel.

maybe the valve guides....

The carbon on the sealing surface definitely looks like there is a small leak between the head and cylinder. IF you can find specs for what the factory considers normal blowby you can build a manometer (google it its very easy all you need is a length of clear tubing such as tygon) and hook that to your crankcase vent and measure the crankcase pressure in inches of H20 while the engine is running at idle at operating temp. I'm somewhat doubtful you will find specs but I may be wrong. Another option would be to do a compression test or a leakdown test. You can find the tools at harbor freight (not sure if you have these stores down under) fairly cheap. That will tell you for sure if you have valves or rings leaking by. An easier but not specific way is just remove the oil fill cap running at operating temp and see if its blowing a lot of exhaust, oil vapor etc out of the fill port. Finally, if the valve guides are worn badly they will take out the valve seals fairly quickly.

What kind or o-ring seals the head? Is it a rubber or Viton compound or something more rigid such as a copper o-ring?

I did a blowby test last night by just having the filler cap sit on the crank unscrewed and it blew right off so the leak is caused by excess pressure in the crankcase. Im looking into the crankcase breather which looks rusted and has condensation but I need to get it off. I dont know how these reed valves work but when I accelerated I didnt really feel or see additional movement of air. Next I will do a compression rest because of its not the breather it must be the rings.
Thanks for your ideas it really pointed me in a new direction amd diagnosed the crankcase pressure and cause of the leak. Hope its the breather.

There were no apparent gases other than what I could smell as being only oil. The engine was cold whe I tested but the oreasure does see high. There is no smoke coming from the exhaust or into the intakes ie clean air filter. Need to perform a leak down test

You know i looked at what blowby is on youtube and is see no gases on mine. its clean. just the filler cap blew right off.

i do have a fouling plug on the vertical only but i thought maybe its because of the leak seeping through.

i guess i need to get a leak down test done.

900ss Piston Ring Clocking

Hi All

im about to change my pistons and rings on a 97 900ss and the manual says to clock them at 120 degrees of each other but it doesn't mention a starting point.
does it matter where to start?

Sorry I haven't been on lately. I wadded up my 899 a couple weeks ago and have been busy finding parts lol. I assume your leakdown test came up bad. No it doesn't matter, you can start at any position you like.

Hi

What happened to your bike?

i decided to rip the cylinders off given the amount of blowby i had and found the oil rings had excessive gapping. the compression rings appear ok but im no expert and the bike does have +70000km.
had the cylinders honed and currently putting it back together..

i need to also break the rings in when i get it going. apparently the right way is to go pretty hard to allow the rings to expand and form a seal.
anyway. hope all goes well.


thanks