05 GS500F with 9000 miles. Runs great. Found a large puddle of oil underneath it this morning, tracked it down to what looks like a breather tube for the air box. Pulled the tank and air filter to find the air box with 1/3qt or better oil in it. So this means compression is pushing past the rings to the crankcase causing it to pump oil right?   This sucks. Any help would be appreciated.

I really doubt it's your rings. On the safe side, do a compression test.

When was the oil changed last? You may have a blocked passage causing abnormal pressures. Or the crank case was filled up with too much oil.

Well I don't have the right size fitting for my compression gauge. I changed the oil in December, and I just needed to add a quart the other day for the first time. Wouldn't a blocked passage mean low oil pressure?

No, low oil levels cause low pressure. High pressure will cause oil to come out the vent tube on top of the motor and collect in the airbox.

Basically, you have a problem. Maybe not a clogged oil passage, but it's not your rings.

Hmm. I'm still confused about your conclusion. High pressure could easily be caused by blow-by and at this point, is the only explanation I can figure. Either way, I hope your right because I'm gonna hate to have to re-ring this thing after 9k.

Quote from: mopardwh on March 19, 2011, 04:14:29 PMSo this means compression is pushing past the rings to the crankcase 

Spot on  air pressure is building up in the crankcase and finding its way out through the breather taking oily fumes with it.

If its not overfilled rings are favourite, it could be they are just gummed up rather than worn. I would pull the plugs and drop some redex/upper cylinder-lube type stuff in the cylinders and leave it for a day or so. Then crank it without the plugs to blow whats left out, it will smoke for a bit when the plugs go back and it fires up but it might just free off the rings.

That's a good idea. I'll try that. I'm pretty disapointed actually. I thought these were suppose to be very reliable engines. 

Quote from: mopardwh on March 20, 2011, 02:15:38 AM
That's a good idea. I'll try that. I'm pretty disapointed actually. I thought these were suppose to be very reliable engines. 

Supposedly... but too many cases of exploding magnetos (or atleast crappy glued magnets falling off) and an all too common issue of spun left side (shifter side) rod bearing has me thinking MAJOR design flaws from the factory.

Really? Then how come you have 3 of them? LOL  For real, this is the first I've ever heard of any defects.

Quote from: mopardwh on March 20, 2011, 09:58:37 AM
Really? Then how come you have 3 of them? LOL  For real, this is the first I've ever heard of any defects.

'cause they are dirt cheap, easy to manage and fun to ride.
Read through past posts and you will see tons of posts about engine troubles.  I'm not saying it happens on a daily basis but the rod bearing failure on GS500 motors usually ends up with catastrophic results and it happens often enough that you will see lots of used ones on ebay, CL, and similar sites for real cheap with blown engines. Same reason makes good used engines kinda hard to find and usually almost as expensive and sometimes more expensive than the whole bike.

More inclined to believe the opposite, given that the bike has been in production for over 22 years and the basic engine design has been around since the 70s you would think that if there was an inherent design problem or weakness it would have been identified and addressed a long time ago.

Yep....plenty of tales of blown engines and shagged bearings in here but have another look and tell us how many of those also include the words "Run it low on oil" or similar?

As for "magnetos".....(surely you mean flywheel-rotors)....again do some research. You will find the GS design is no more or no less reliable in this area than any other similar design from another maker.

Do a search, you will find certain and more common models are far more problematic. If I had to say what the biggest problem GS5s are prone to I would say the carbs are prone to clogging up and going out of tune/sync. Petcock failure is another biggie but how many times have they changed the design to try and overcome it....must be 3 or 4 times now.

Quote from: tb0lt on March 20, 2011, 10:13:46 AM

Quote from: mopardwh on March 20, 2011, 09:58:37 AM
Really? Then how come you have 3 of them? LOL  For real, this is the first I've ever heard of any defects.

'cause they are dirt cheap, easy to manage and fun to ride.
Read through past posts and you will see tons of posts about engine troubles.  I'm not saying it happens on a daily basis but the rod bearing failure on GS500 motors usually ends up with catastrophic results and it happens often enough that you will see lots of used ones on ebay, CL, and similar sites for real cheap with blown engines. Same reason makes good used engines kinda hard to find and usually almost as expensive and sometimes more expensive than the whole bike.

I found just the opposite - I was looking for a bike with a bad motor (because I had a good one) but found very few, and none close enough to me.

Well today I went to 3 hardware stores and 3 part stores in search of a fitting the size of the plugs without any luck. Aside from buying a whole new compression test kit for $45 I decided to skip the test for now. Instead, I bought a bottle of "Rislone Compression Repair" and a new set of NGK's. I poured about an ounce down each cylinder and bumped the starter w/out the plugs a few times. Let it set for about an hour. I cleaned out the air box, put the tank and plugs back, set the choke and let it run for about 15 minutes. The smoke cleared after about 5, and still no signs of blow-by. I'm gonna put it all back together and hope for the best.

Did you smell that oil on the ground and in the air box?  I was going to use my old 97 GS that had been parked for months once when I was working on the newer 02 GS so I pulled the dipstick first to check the oil before starting it, bike was on centerstand.  The oil was about a quart overfull and when I put my nose to the dipstick and smelled it smelled like gasoline.  Bike was parked with the selector switch set to prime and the gas had leaked past a carb needle valve into the crankcase.

A GS500 with 9k miles on it with blown rings?  I doubt it unless you ran it without oil.  Most likely the crankcase was overfull with a oil/gas mixture.  I put 80k miles on the 97 GS and have 85K miles on the 02 GS and counting with no serious problems like that and expect to go to 100k miles with nothing more than routine servicing.  Oil consumption increases with many miles but that's not serious or unusual for an oil cooled engine.

I've never touched the carbs on either bike nor the starters, alternators, regulators, ignition pick-ups, modules, etc on either bike so I still consider them reliable bikes.  Compression check, well I do check mine regularly with the finger over the plug hole and crank test;  if the pop sounds right the engine is right.   

Defenitely no gas in the oil I would have noticed that right away. I run Royal Purple and it stays really clean. There is nothing wrong with it now. It's ran great for the past 2 days since I worked on it, and not a drop of oil. The only thing I can figure is it may have been overful, or there was carbon build up or something on one of the rings. I don't have a center stand yet so I guess I should be more careful checking it if that's what it really was. Also, I remember just dipping it down instead of actually running the threads down on the dipstick after I wiped it off, that would make a small difference too.

Quote from: tb0lt on March 20, 2011, 08:31:01 AM

Quote from: mopardwh on March 20, 2011, 02:15:38 AM
That's a good idea. I'll try that. I'm pretty disapointed actually. I thought these were suppose to be very reliable engines. 

Supposedly... but too many cases of exploding magnetos (or atleast crappy glued magnets falling off) and an all too common issue of spun left side (shifter side) rod bearing has me thinking MAJOR design flaws from the factory.

When I spun my left side bearing it was because the magnet broke off and got in there. Every problem Ive had with the bike was my fault, and this is probably the case with id say 99% of GS's out there.

Quote from: mopardwh on March 22, 2011, 07:38:56 PM
Also, I remember just dipping it down instead of actually running the threads down on the dipstick after I wiped it off, that would make a small difference too.

It should actually specify that detail in the manual. I believe most bikes require you to NOT thread the dipstick down when checking the oil level.

Quote from: Big Rich on March 22, 2011, 11:41:28 PM
It should actually specify that detail in the manual.

Errrr.....it does.

are you sure its coming from the breather hose? if not sure could it be leaking intake valve seals?

Defenitely the breather hose the carbs were clean.