Gabriel, it's very interesting that you mentioned this problem. About a week ago I had the identical problem on a Sachs 4.2. When cold it would start good and run good. Shut the engine off and I couldn't get it to restart no matter what I did until it got back to ambient air temperature. I pulled the plug, some kind of Bosch, and it looked very good with a light tan color. I replaced it anyway with a new Champion RCJ-7Y. Problem solved. Wish I had done that about 3 hours sooner.

I would like to hear a good explaination as to why it will start good cold and run good but will not start hot. Or maybe even a good theory. What does a "weak" plug mean? Weak how? I understand what a weak battery is but not what a weak plug is.

Ken