View Full Version : Stihl Br420 magnum over heating

09-09-2010, 05:58 PM
I just replaced the bearings, seals and top end on a stihl br420 magnum. it seems to be running real hot. it runs great but after running it for about a half hr and at shut down it starts to crackle like it is over heating. the engine shroud cover is so hot you almost can't touch it. any idea why it is over heating.

09-09-2010, 09:30 PM
I pulled off the muffler, the cylinder walls, piston and rings still look good. there is a little brown on the side of the piston close to the top past the rings. looking thru the exhaust port it looks ok just that little spot of brown that is barely visable on the right side of the exhaust port. not sure if maybe that carburetor is doing this. The low set on the carb is at 2 turns and the high set is at 1 and a quarter turn. I'm fixing this for my mothers friend. could the carb be bad which is causing it to run to lean. the shroud cover only gets real hot on the exhaust side after running for a while at full throttle. any advise would be appreciated. Thanks

09-10-2010, 10:02 AM
I thought there were suppose to be highly trained machanics on this site. how come I'm not getting any help with this. Thanks again

09-10-2010, 11:34 AM
Cat muffler? Those things can get really hot. Since you buy junk stihl and fix em up do you have any other mufflers laying around?

09-10-2010, 11:42 PM
You need to read the plug.

09-11-2010, 12:22 AM
I installed a cat muffler. do stihl br400 muffler run any cooler. the plug color is ok. tan brown. is it dangerous to run the cat muffler. I couldn't believe how hot it got. felt like the shroud cover was almost hot enough to melt.