change a 400ex piston

[jeremy_283]

I've worked on everything on the outside of my bike and I've changed my 400ex's clutch before and I was wondering how hard it would probably be for me to change my own piston?

[polakmike7]

did it myself n im 15..u jus need the machine to compress the sleeve out if u are changin the sleeve or resizing it. and buy a service manual it shows u everythin.

[jeremy_283]

any other opinions?

[wilkin250r]

It's not terribly difficult. Just keep a few things in mind.

Pressure wash everything. Then take your plastics and tank off, and pressure wash again. You don't want dirt getting inside your engine.

Everything inside your engine is a little more critical. You can under-torque or over-torque the bolts that hold on your muffler, no big deal. But it IS a big deal inside your motor. A good torque wrench is a must.

Take your time. Keep things organized as you take them apart, plastic baggies are great. Nobody is going to think you're a nerd if you keep a notebook. Draw an outline of your head cover on cardboard and punch your bolts through in the proper place to keep them organized.

[250X_project]

yeah, it's not bad, just keep things clean and get a manual for specs on head bolts especially. I would suguest a valve job while its apart, then an adjustment (specs in manual) when head cover is back on. oh and you could always cam it...

the valve job is very simple you'll just need some valve grinding compound. put a plug socket on the spring retainers and tap it to get keepers out,take off springs, lap valves replace seals and reassemble....REMEMBER clean compound off and a little vale lub on stems when put back together would be good too.

and another thing: you would have to time it, put piston at Top then face both lobes down with lines on the gear flush with the cyl. head

good luck