I just put on a new Yoshimura full system stainless exhaust on my 07 YZ250f and the bike now takes 8-10 kicks to start when cold whereas it would start on 1-2 kicks with the stock system. Jetting changes only include a 50 leak. This was done last year so the stock pipe has been working great with this. Otherwise I think it is stock (too many bikes in the barn...can't remember what changes I made to which bike ) Once the bike is warm, it seems to start up ok. I have only ridden around the block (neighbors love me) but it felt good with no popping. Also idles very smooth. The one abnormal thing I can think of is the installation instuctions called for reusing the "stock exhaust port gasket" and I did not see any gasket. Any ideas?