Where is the oil going?

[flyingace]

It would be great if I didn't have to take the head off because I would need to replace the head gasket this time around. I'm going to study the possibility very carefully.

Thanks again everyone.

[TheCafeKid]

Those both sound really plausible, and pretty easy actually, but, if and when I do a valve seal job, it is MY belief that the head should be removed completely, the valves taken out and cleaned, and the seats inspected. Oil passing the seals will build up on the back of the valves as it burns, most times incompletely, and cause the valve not to seat all the way, making your valve clearance readings false. Im not saying thats what everyone should do, nor that its the BEST way, but just something that *I* do for piece of mind. I also generally clean the piston crowns, and check the bores while im at it. If you're carefull, you can usually get the head off without disturbing the base gasket, but not always, so i would also pull the jugs, inspect the pistons and rings, and replace the base gasket. If need be, the bores can be honed as well. Its a full afternoon job, thats it, and IMO well worth it for peice of mind. Keep in mind that generally, if your bike doesnt sit for a long period of time allowing the valve seals to dry out, or you dont drag race, those seals will last quite a few 10K miles, so i consider it a good time to do all that stuff anyway. Hell, as far as I know, the GS1100GK i got from Grandpa, which will likely get a top end job done this winter, has NEVER had the head off, and it has 140ish THOUSAND miles on it and just BARELY leaks thru the seals a bit on start up. Pretty impressive really.

[gearhead13]

145-127 psi compression? seems kinda low for a new re-ring. I think to expect at least 150 on all.
My bike with 65,000 km's has 145-120 psi on it.

[TheCafeKid]

145-127 psi compression? seems kinda low for a new re-ring. I think to expect at least 150 on all.
My bike with 65,000 km's has 145-120 psi on it.

They dont sound rediculously low to me, and they're well above service limits. Remember that pistons are generally NOT exactly the same size, and thats part of the reason the rings are springy to begin with. At any rate, I do have a concern, and it may be way off, but I THOUGHT that i remembered reading in my various manuals that if the cylinders were a certain percentage apart from eachother in compression, that there may be a problem. Im not possitive, but you may want to check that out. While they are all above service limits, they may be bellow the required compression in relation to eachother. This sort of makes sense to me in my head, as if your cylinders compression is alot higher on one or more than another or more, the crank may be loaded unevenly, resulting in issues. Plus the cylinders may load up to the point where it seems to lope when it hits a low cylinder vs a high one. In which case you may have a cylinder wall issue, or a valve seating issue? Im not sure again, so you might want to investigate that theory.

TCK

[Piston720]

Good Morning All
I have the same issue as Flyingace, and have found this thread very helpful. I have a 79 GS850G with 90000Km(56000miles). I started loosing oil around 70000Km at the rate of 1 quart every 2000 miles and more when riding loaded through Pennsylvania and the Blue Ridge. I noticed there was oil in my air box being blown from the cam cover tube that feeds it, this in turn was fouling my plugs.
I disconnected the tube to air and plugged the air box hole. This seems to have solved that problem.
The bike runs great, compression is 125 even on all four cylinders. I do notice a little whitish exhaust on startup and you can barely smell oil when riding behind me.
There is not a visible leak anywhere and the engine has never been apart other than to do shims.
I have recently purchased an 83 GS1100 and plan on taking the 850 apart this winter to check the seals and rings as you all have mentioned in your responses. This will be a first for me and am looking forward to it, espescially since I now have another bike to ride if things don't go well.
By the way I am the original owner of this 850 and would love to see it continue for another 90000K.

[flyingace]

They dont sound rediculously low to me, and they're well above service limits. Remember that pistons are generally NOT exactly the same size, and thats part of the reason the rings are springy to begin with. At any rate, I do have a concern, and it may be way off, but I THOUGHT that i remembered reading in my various manuals that if the cylinders were a certain percentage apart from eachother in compression, that there may be a problem. Im not possitive, but you may want to check that out. While they are all above service limits, they may be bellow the required compression in relation to eachother. This sort of makes sense to me in my head, as if your cylinders compression is alot higher on one or more than another or more, the crank may be loaded unevenly, resulting in issues. Plus the cylinders may load up to the point where it seems to lope when it hits a low cylinder vs a high one. In which case you may have a cylinder wall issue, or a valve seating issue? Im not sure again, so you might want to investigate that theory.

TCK

The Haynes manual has something like compression between 120-170 with no more than a 28 PSI difference between high and low.

Just to clarify, my rings are new but a complete ring job was not done. I mixed/matched pistons from this and another bike until I got within spec. Then roughed up the cylinders and installed $25 EBay rings. That represents the total cost - $25. I think the readings are pretty respectable after 15K miles considering the shade tree factor.

[TheCafeKid]

The Haynes manual has something like compression between 120-170 with no more than a 28 PSI difference between high and low.

Just to clarify, my rings are new but a complete ring job was not done. I mixed/matched pistons from this and another bike until I got within spec. Then roughed up the cylinders and installed $25 EBay rings. That represents the total cost - $25. I think the readings are pretty respectable after 15K miles considering the shade tree factor.

Definately respectable. I wouldnt consider myself much more than an adequately experienced shade tree mechanic myself. I am by far no expert. But, this time last year, I didnt even know more than adjusting the valves. Now i can pull a top end apart and rebuild it and have the bike running in an afternoon. Its not tough, once you know what you are looking at. If you gather all the necessary parts, you could start in the morning, and be taking it out for a shakedown run before dinner. I have yet to crack the cases on a GS, but i have seen many jobs done via pictures, and feel pretty confident i could do it rather easily as well. Getting them apart to begin with seems the hardest part to me. If i have the time between or after all the other projects I have on the board for this winter, I may just be pulling a GK motor apart and replacing or shimming out the bevel gears and perhaps getting the tranny back cut. Who knows. It really is quite a relief to be somewhat confident in this stuff tho, simply because I know that other than finding the parts i need to repair it, if something on any of my bikes break, I can generally fix it. Makes one not so timid about crackin the whip on em...