I have a 12.1, hotcam 2, port and polish, yosh full exhaust with k&n filter, kibblewhite valve springs and the problem is when i go to start it. depending on were the stoke is it wont turn over. If you hit the starter under compression it will want to stop but when its not under compression it instantly starts. The motor runs great just having this problem. I saw on other posts that their could be a decompression pin problem. The bike has only been started about a dozen times and each time its getting better. The shop that done the work says it will most likely go away soon that its a matter of braking in. I think he is right being as its getting better but i would like your ideas.

 

I have the same mods and mine has started instantly every time, like one full revolution and then it's running. If the bore is that tight, I'd be worried. Who built the engine?

 

I had a shop in north platte do the motor and i am sure he wouldn't have done the work if the bore was to tight. He specialized in 400ex's. I'm thinking it has something to do with the pin or maybe it justs need to be broke in but who knows, well just have to see what happens

 

My 686 would barely crank over after the rebuild, I'd have to hit the button a couple times as it would crank a turn then stop. I replaced my battery with a YTX20BL and it helped but no major improvement came until I replaced my starter oneway. I dont know the relationship with a worn oneway but it did make a difference. I put in the LA design oneway and my rappy starts right up every time now. Btw I'm 12:1 with HC stage 2.

 

My story is the same as Mr45auto. It could be a couple things other than the one way, decomp pin, valves not properly adjusted, cam chain stretched, cam timing off, ect... I would check everything you can, but I bet its the one way.