400ex stroking

[Fatal]

Hi all i hav a 2003 400ex already hav a full yoshimura rs3 pipe and a curtis advenced spark but he is leaking a lot of oil i just bring him to my quad shop. i buy a 11 to 1 wiseco 406cc piston with a stage 2 hotcam new timing chain with new sprocket for timing chain i would like to know if i will gain on top speed with the hotcam stg 2 or not and if i will be happy riding em after this tune up i got all pieces at cost price cause i work in a shop i will hav him saturday night ( riding is missing for me ) 2 week now. thnx for ur awnser Alex

[F-16Guy]

If your engine was stock before except for the pipe, you will see a huge improvement with your new parts. The Stage 2 cam will give you good top end power, and the whole upgrade will make your quad faster because you will be able to turn more RPM's in every gear. My only advice would be to remove the Sparks timing key now that you have the new piston and cam. It will have too much spark advance and cause your engine to run hot and possibly overheat. Also, make sure you install larger jets in the carburetor before you start it the first time. If you have stock Kehin jets now, you'll want to install in the range of about a 162-165 main jet and a 40 or 42 pilot jet. After break-in, you can lean out the main jet a little if you need to; it's just better to be a little rich during break-in.

[Fatal]

you say that my motor will blow off if i let the sparks in ?

[F-16Guy]

It might not cause any damage right away, but it will definitely cause it to run hotter. With a modified air cooled engine, you want to keep it running as cool as possible. The power gains you got by installing the Sparks key are nothing compared to the power gains you'll get with the piston and cam, even with the Sparks key removed. It will be better for your engine to replace the Sparks key with the stock woodruff key. I hope you understand what I mean; my French is a little rusty! :D

[UglyMotha™]

i have a 416 with a 7mm stroke making for a 452 13:1 compression and roughly every other thing you can think of to do to a engine and i'm running the sparks key and she runs no hotter than a stocker on 110