400ex running hot?

[mcgrath]

ok, fresh rebuild with an 11.1 high comp piston, k&n filter. I got this machine blown up and in boxes. Rebuilt and put back together runs mint but seems to run awfully hot. It had original piston in it when I got it but melted down. the only thing with the setup that Is different is the piston. Do I need to rejet for this? I just took it out for a couple of rides around the bush with my kids so I was riding pretty slow. Would it run much cooler under normal riding conditions or is it the jetting? thanks first 400ex

[MtnEX]

These run hot man... and they will cook your legs when riding slow.

Pull your plug though and have a look at it. It will give you a general idea where you are on jetting.

I can tell you from today though... if mine gets a bubble of air or water in the gas, it will run sad and lean backfire... and that is with my jetting on the rich side on the main.

[MtnEX]

You will need the stock tool... or a strip of the Stanley deep well sockets from walmart (18mm) or other deep well thin wall socket and an extension to get the plug out.

Check for trash before removal too.

[rob_990]

did you bore it out?was it backfiring or anything?

[mcgrath]

right on, Im gonna take it out for a good ride today and see how things are. runs great all the time, idles good, pulls good no back fires. driver mcgyver.