I just picked up my ys 110 that has been sitting for about 2 years and it seems that the valves arent working. I pulled the valve cover and the rockers dont move. I can't get the cam cover off to see if the cam is turning... the cover spins but wont come off. anyone have experience with these engines??

You might post this in the Engine Manufacturer's Direct Support Forum - there's a YS sub-forum.

Oh, not willing to pull my YS FZ110 apart to see how it's put together 'cause I'd probably break something ...

There is a complete break down and rebuild in the YS support of the YS .91, great photos and it walks to through the process.

i can't find it . can you post a link to that info on rebuilding w/ pictures thx

httptech.flygsw.org-ys91.htm This is as good as I can do for you. I don't know how to bring something like this over to another thread. It's so well writen I have it saved in my favorites.

thx i 've got it now

httptech.flygsw.org-ys91

FWIW - this is a pdf file format of the article referenced by Gene ...

A heads up on the gas porting. I was doing it like the instructions show. Then I got hold of a YS that was gas ported by YS service and they drilled 4 holes. Now days the new YS engines come to you ported but they have cut slots. I asked Bill Baxter about doing it to OS engines and he said it wouldn't hurt. I haven't noticed any real power gain but it must be doing something or YS wouldn't be doing it. I don't think it's needed but I do it anyway and if you send in an engine to YS service they do it for you free of charge. It used to be free anyway.

Gene - are you suggesting that the porting can be very effective for any ringed engine?

Yes. All it is doing is putting outward even pressure on the ring for a better seat to the wall of the cylinder. I was wanting to do it to an OS I was rebuilding so I asked Bill if it was OK, he said yes.