So, I replaced 2nd gear in this 660 a month or so ago. And, while I had it apart I took the cylinder to a buddy to have him check it out. He said it was worn beyond specs. I don't remember how much tho. But the owner didn't want to pony up more money to fix that at that time. My buddy said that it would run fine for a while, maybe a little noisy. So it' all back together, the owner has had it out and riding a couple times. Everything is fine he said. He brought it back yesterday for a new chain and sprockets. He started it up and it smoked alot. Blue smoke. He said that it hasn't done that. Well, I fired it up yesterday and it smoked alot when it first fired up. Then it kinda petered out. It would blow a little with a burst of throttle. What seems to be the cause? I'm thinking that it might be the valve guide seals IDK. I have some new seals that came with the gasket kit when I did the trans. What does it take to change those seals? Valve spring tool? Any thoughts, advice? Thanks!

Yep, valve guide seals. IDK if there's room to do the work without pulling the head. If you try, get or make a air fitting to fit the spark plug hole. I've taken a old spark plug, break out the ceramic and weld/braze a air fitting to it. Pressurizing the cylinder will hold the valves closed after the cam is out and you remove the valve keepers. Or, pull the head and I've use a standard, full size compressor on 700's. Speaking of 700's, I found the casting where the seal mounts is easily broken off. Just be careful. If you pull the head, I would at least lap the valves.

Alrighty thank you. I think I would just pull the head. It isn't that difficult and probably safer.

Besides a valve spring compressor you should have a pencil type magnet to remove and install the keepers. When installing the seals a little spit helps them slide easier. Just not mine, haha!