building the ultimate sleeper???

[jlhughes750]

well i tore down the 400ex today,(the wifes quad)

Its an 02 and its real clean...it has been ridin and raced hard a few times(always an extra quad)....its always had a clean filter and oil, and always ran a stock pipe...... I used it run 1-2 times a week out back while the YFZ was being prepped for the floowing weeks races.. It was also raced in several GNCC races in the stock class.. Got me a top 10 overall in the AM race in NC a few years back...Then a 5th at Rausch GNCC 2 years ago!!!!!! She's been a great quad, always there and able to be depended on when the R of YFZ was torn down!!

Well I had her out 2 months ago in the snowy coal pits of Hazelton Pa. We were running hot laps on a little mx track when it locked up ......done would not even turn over?? I noticed oil on the side cover and upon further inspection we saw the drain plug had come out!!!! After it cooled we fashioned a new drain plug from some stuff on the ground and ran back to camp for some oil!! ..............well it turned over and ran fine!!!!!!!!!!! it did make a substantial amount of noise before it started runnin good???

So i tore it down today...I new before this last ride that it was due for a top end!!! All i found was a ring out of place that scored the wall and tore up the piston!!!! great no seriuos damage....

TO THE POINT....since its my practice bike and I like my neihbors, I want to keep the stock pipe on!!!!!!!!

Heres what i think, Whats everyone else think....

fresh bore....slightly higher comp. piston and get the head/valves done real good???

[TheFontMaster]

If you really want a true sleeper, drop in one of those 650cc air cooled on/off road bike motors. Someone else on the site did that, and he still used the stock 400ex tail pipe. Also at a glance it looked just like a regular stock 400ex.

I wouldn't call what you want to do the ultimate sleeper, but it seems like a good plan to get a little more go out of your 400ex.

A little off topic, but the ultimate sleeper would be that 650ex i mentioned above, but then add aftermarket shocks, PEP, Elka, etc without and piggybacks, or ressies, and put shock covers on them so they looked like stock shocks when they were really top of the line shocks.

[JDiablo]

that sounds good,you can grind the welds down on the header and cut the stock pipe 2-3 inches and install the end cap back on without it being noisy