I found a pinched crankcase vent hose and fixed it but the base is still leaking. Is my only recourse to tear it down and replace the O-rings?

 

I have a base leak on an evo, and I just live with it. Might fix it sometime...or not.

 

It's on a 13 twin cam and leaks enough to drip off both sides after a 100 mile ride.

 

That would drive me nuts. If it were mine, I'd tear it down and replace the o rings. I don't know how else a person could fix it. Might be a good time for a Fuel Moto 107 kit.

 

Do I just oil the new rings, slip them on and put it all back together?

 

X2 good time for a big bore kit

 

I would buy an upper engine gasket set because you'll need most of them. Follow the steps for disassembly and reassembly in the appropriate service manual. I don't think you oil the cylinder base o rings. Just make sure everything is clean and be careful not to damage them when reinstalling the cylinders. Don't forget the small o rings for the rocker box oil return passages.

 

Invest in a service manual. There is a very specific sequence to torqueing the heads/cylinders with a tq wrench. You will also need ring compressing tool to get the cylinders back over the pistons. Other than that, taking the top end apart is easy after you remove the fuel tank.

 

If you are really smooth you don't even take the cylinder all the way off. Just lift it enough for the wrist pin to be exposed. Remove the circling and take out wrist pin and pull cylinder off with piston hanging out the bottom. Don't know that I have the smoothness for that, but it can be done.

 

Okay; if I had a dripping, leaky O ring on a newer TC, I'd fix it. I agree with everyone, the service manual is a must.
Also, I'd be interested in why it's leaking. If I got the cylinders off, and the O rings looked fine, I would consider having someone check the trueness of the cylinder bases.
I've done this job, and it's do-able with no special tools. You can compress the cylinder rings with large, worm-drive hose clamps.