I bought a used Saito .65 from a reliable person last year and it has run just fine. But, I've noticed over the past few months that just hasn't been sounding very healthy. Yesterday, it would hardly power up enough to keep the plane in the air. All glow plug/fuel system issues are OK. My gut feeling is that there is an internal issue like bearings or? A friend is going to lend me an exploded view of this motor but otherwise I'm on my own. I hate to just trash it and I see it as a bit of a challenge and maybe a learning experience if I attempt to fix
I wouldn't expect go receive a complete tutorial but if anyone can give me a few guidlines in regards to disassembly or what to look for I'd be forever grateful. Once I can figure out what's wrong I can then decide on whether cost of fix is worth it. Thanks in advance.

Norm, there are several tutorials in the Club Saito thread.

It could be that the air is cooler now and you will need to richen your mixture a little?

Norm:

First check the valve clearance. This is the most overlooked part of four stroke maintenance regardless of brand.

Then if the cylinder compression still feels good with the throttle open, either the bearings are bad or you've coked the valves and ports.

Bearings:

If there is any roughness in turning the crank you probably have used the bearings up. There should also be a lot of bearing noise, but some people just can't hear it. Grab the prop - if you can feel any movement other than rotary the bearings are bad.

Pull the exhaust out of the cylinder and look in at the valve. If you see huge blobs of black you have coked the valves. Check the intake too, but it's much less common there.

Let me know what you find and come back.

Bill.