Compression question.

So i did a compression test at cold (i read that cold or hot doesnt matter all that much) And here's the results:
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Right cilinder dry: 90 PSI
Right cilinder wet: 100 PSI
Conclusion right cilinder: Valve's or valveseat worn or broken.
Also possibly head gasket leak, but i don't hear it, so i dont think thats it.
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Left cilinder dry: 90 PSI
Left cilinder wet: 150 PSI
Conclusion left cilinder: Pistonring worn out.
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Im so guttered :S There's no way im going in for a head revision, not after the last time i tried to take out and refit the engine. It was such a hassle.

Got a chance to spot the spark plugs aswell:

Right:


Left:




Suggestions regarding this coloration? i'd say it could be a tad richer, but then again, im not completely confident when it comes to spark plug reading.

Wow. What's the spec call for? Around 150 cold on both?

I can't speak for the GS500 in particular, but you may be able to pull the entire top end off (including cylinders) with the engine still in place. Again, I can't speak for the GS500,  but it is usually easier to pull the engine than trying to work everything out of the frame.

Did you hold the throttle wide open while checking compression?  Those look like closed throttle values, I checked my compression last year with 100k miles on my 02 and it was much better than that.  Actually about 140 psi in both cylinders before adding oil.

http://gstwins.com/gsboard/index.php?topic=67148.0

Right Rich, I pulled my 02 head with engine in frame.

Throttle closed would give me around 45 psi per cilinder (tested to see how much of a difference it would make.)

Good to know that pulling the head of CAN be done in frame. I was thinking, i can buy a second hand head for 50 euro's and for 50 euro's more, i have a cilinder block. Maybe its worth buying a head and cilinderblock for 100 euro's, and build it on the bench. Make sure everything is tightly fit together, give it a nice paintjob. Make or buy a custom exhaust for it. Take my time, Taking it Slooooooooooooooooooooooooooow :p You knaw what im sayin!

Then again, in a year i'll get my full license, lifting me of the 35KW law. Then ill probably sell the Gs500 to get something with a bit more umpf. So i dont know if it'll be worth it.

Okay, a question. Given the compression i have, would i be missing out on a lot of horsies? This is my first proper motorcycle, so i have no referencepoint as to how fast this bike should go.

As you said, I would find a complete head to swap in. Can usually be found for less than $200 if you look long enough. Then just a few bucks more for the gaskets and copper washers. You should probably replace the piston rings as well? Not really my area of expertise but I did swap a 2005 head onto my 2006 GS a few years back. If you fiddle with it, you can do it in the frame.