wheelewilly

400ex a ton of black carbon on valves why

6 posts in this topic

My 2003 400ex has been smoking forever so I broke down and bought a new wiesco 416 piston and stage 2 hot cam,but when I tore it down the bottom of the head where the valves are was covered with black really hard carbon and I mean a lot also my spark plug was one big ball of the same stuff my head pipe looks the same inside is it valve seals or just bad rings Im going to replace the valves any way with the rebuild but I m just wondering if it could be anything else?

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its from all the oil being burnt... Probably mostly from the rings. If you going to put new valves in put new seals in for sure and i would have your guides checked.

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rings. get a cleanup bore and install that new piston and ride it for 10 more years. :yes:

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You will need to have the cylinder bored to 87mm to fit that piston, and I think you have to use top end gaskets made for an oversized piston.

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