Top end rebuild? or new(old engine)

[SRwitt]

Well what started out as me thinking carb issues turned out to be totally wrong.  I just got my bike back from the shop after having them perform a diagnostic on it.

Results are low compression on #2 and 3.  Cylinders one and four were at 125 psi and 2 and 3 were right around 50 psi.

My question, with the guidance of a factory service manual how hard would it be for me to do rebuild the top end which is what the shop is saying needs to be done. I'm fairly confident in pulling things apart and putting them back together, I have only common tools, socket set, box wrenches, allen wrenches bla bla everything besides specialty stuff.  Or would it be easier and or cheaper to just cruise the net hoping to come across a running engine.  

I don't really have the $1300 quoted to have the shop do it,  but I do have the manual now.  I was quoted about $500 for the parts but i think that was only for new pistons and rings for 2 cylinders plus all the miscellanious o-rings, seals and other parts which is a lot more reasonable for me to drop on the bike at the moment as long as I would be able to rebuild it myself fairly easily.

Anyone have any opinions as to why 2 cylinders would be so worn with only 9000 miles on it.  There was no noise made or anything it just suddenly lost power.

Thank you
Shawn

[Thief400]

If I was a betting man I would bet on a blowen head gasket between the 2 cylinders

[Maniac]

I'm with Thief, the two outer cylinders sound just fine. The two inners are -dramatically- bad. It does sound like a blown head gasket, you may be able to get away with just replacing that.

Have you been noticing any missing engine coolant? Oil in the coolant? High-pitched whistles from the engine block?

[Dragbike]

I would definitely do a valve adjustment before condemning the motor, could just be tight valves. Then do another compsion check. One thing you can do too is a compression check, then squirt some motor oil in the cylinders and do another check. With oil in the cylinders and the compression goes up you can tell if it is the valves or the rings.
Brent

[gsxr400 racer]

I would definitely do a valve adjustment before condemning the motor, could just be tight valves. Then do another compsion check. One thing you can do too is a compression check, then squirt some motor oil in the cylinders and do another check. With oil in the cylinders and the compression goes up you can tell if it is the valves or the rings.
Brent

Now ther is a smart man!

[SRwitt]

I dont want to condemn the motor, I just figured if I could find one for cheap enough now I would save the hassle of the rebuild until I have more time to sit and work on it.  I was talking with a couple of guys I work with and we all thought about a blown head gasket between the two.  I haven't looked into the fluids yet.  I was going to adjust the valves when my manual came in but it broke before that.  

Thanks for suggestions keep them coming I want to drop the engine from the frame and tear into it this weekend.

Shawn

[Red01]

With oil in the cylinders and the compression goes up you can tell if it is the valves or the rings.
Brent

If you squirt oil in the cylinders and the compression goes up, it's highly likely the rings are shot. If there is little or no change, then the problem is not rings... it could be valves, or it could be a head gasket.

If #2 & #3 are nearly the same compression numbers and if I were a betting man, my money would be on the oil squirt test not making much difference and the head gasket is blown. This fix would be a cheaper than a rebuild, but surface flatness of the head and block need to be checked and resurfaced if necessary.

[SRwitt]

Looks like a case a beer and the bike this weekend.  I'm hoping on it being the head gasket.  As far as know the head and everything should be in good shape I dont believe I overheated it.  The bike only has 9k miles on it.