Oil leaking from exhaust 81 GS550T

[Guest]

Hello all,
I recently acquired a 1981 gs550t with only 1000 miles on it and all stock parts in good condition. The bike had been sitting for the last 34 years so I have changed all the fluids, filters, and rebuilt the carbs. It was running well for about 100 miles until I started it up one morning and oil started leaking from the exhaust pipe. The oil was leaking from one of the exhaust clamps on the underside of the bike. I pulled the spark plugs and the #2 cylinder plug was covered with oil. After some googling i narrowed down the possible problems to either some broken rings on the piston, head gasket, or leaking valve seals. I pulled the cylinder block and found the gasket to be good, the valves to be sealed, and none of the rings were broken. The only thing i noticed was that the lower compression ring was jammed in the groove on one side of the gap in the ring. I had to put some effort into wiggling it out of the groove. Does anyone know if this is an issue that would have caused a significant amount of oil to be getting above the piston? Or does anyone have any other ideas as to possible problems? I really want to make sure i rule out all the possible problems before i reassemble the engine.

Also thanks to everyone on this site for making it an awesome place for shared info on these bikes. It has helped me save a lot of time and money. I really appreciate it!

[gsrick]

Sounds like you may have found your problem already. The oil ring does exactly as it's name implies. It controls the amount of oil that can get into the combustion area by scraping the splashing oil back down off the cylinder walls. Did the bike smoke any? If it did, was it all the time(rings) or only for a minute or two after start up(valve seals)? Was the cylinder firing before the plug oiled up?

Almost forgot, welcome to the site.

[kazak_the_dog]

The oil ring looks fine. It was just one of the compression rings that was a little bit jammed into the groove on the piston. Im not sure if a bad compression ring would cause oil to get above the piston. The bike was smoking and continued to smoke as oil was gushing out of the exhaust pipe. I did not keep the bike running long though after i saw the oil. The plug was firing just fine before.

[qcktvr]

Hi Kazak,
I share your concern and can't picture enough oil passing one stuck piston ring to be dripping from the exhaust.. "If" that plug had been firing I think you would have been in a blue cloud...
NOW, #2 cylinder supplies the vacuum to the petcock, at least on my 1150, and when the diaphragm fails raw fuel enters, which will wash away the oil and maybe = stuck ring and high cyl wear.
I ran for a year with a $20 rebuild kit but the lever was too stiff and ended up buying a new petcock.. luckily still available.
Good luck

[tkent02]

NOW, #2 cylinder supplies the vacuum to the petcock, at least on my 1150, and when the diaphragm fails raw fuel enters, which will wash away the oil and maybe = stuck ring and high cyl wear.

Most likely the petcock is leaking fuel, either through the vacuum line or by just not shutting off completely, it runs past the piston into the crankcase and mixes with the oil, the oil level in the crankcase gets too full, the excess oil/fuel has to go somewhere so it does.

That ring being stuck is common on bikes that have sat forever, a little hard riding and they free right up.

[kazak_the_dog]

How can i test the petcock to make sure it is working properly?

[Brendan W]

Pull off the hoses and check that no fuel flows out either hole set to ON or REServe. Block the delivery hole and see nothing comes out the vacuum line on PRIme.