Well Thanks in advance to ANY help I can get. I will try to make this short. Rebuilding a 185s , new rings,ground valves,new cam chain,sprocket and cam tension rods. Put all back together set timing , has good spark but does not fire. Checked timing several times and everything looks like it should start up...but it does`nt seem to be firing. I don`t even get a back fire. Compression is at #80. Seems that should be enough to at least start. I get no fire when I spray starter fluid. I have YOU TUBE videos and tried about everything. Any suggestions. One other thing can some one tell me which cylinder stud the "o" ring goes on. Thanks again.