What's the Most Likely Cause?

[livin4weekend]

Last fall I made the transition from mountain riding (7000'+) back to dune riding. Seems I neglected to rejet for the lower elevation. Didn't realize it until it started smelling like it was running hot. I've got the proper jets in now but ever since this episode it smokes and burns a measurable amount of oil. Smoke is worst when started cold.

Is this a result of just piston/ring/cylinder damage or might the valves/guides be involved?

I'm looking a putting in a 416 kit and am wondering whether any head work (machining) is going to be required or if I can limit the machining just to cylinder work. I am planning on putting in a stage 1 cam at the same time.

Any first hand knowledge is appreciated.

[Bill Fuller]

Sounds like the valve guides/seals to me.I would just go with the 416 and freshen up the top end at the same time.You will not need any special work done,maybe relap the valves.I would suggest(depending on year)you replace the timing chain as well.Good time for a new clutch also.While you got it down check that swing arm pivot bolt remove it and grease it.


P.S.
Welcome to the site,lots of good info here!

[44oEX]

that sounds about right

[Engine Tech]

You can send me your engine and I will hook you up with a great engine that is very reliable. I even offer a Heavy Duty Cam Chain for the 400EX. You can view a few available options @ www.enginetechatv.com/

The website is still in progress but it's not bad. We do offer other kits and products so if its not on the site e-mail us and I will hook you up. If you have not heard of us you will as we are working on an extensive sponsorship program for the 2005 season with some pro GNCC Riders using our engines. Possibly GNC as well.