how much more power?

How much more power will I get if I ran a wiseco .040 bore piston with 11:1 compression? How much with the .080 bore piston with 11:1 compression. I do mostly all trail riding. The 400ex is all stock but I am wanting to add the K&N filter kit and a pipe later. Will I have to have the jets redone with the bore kits? How reliable are the bore kits? Will I still be able to run pump gas?

[Blackguywithouta400]

You will be very happy on the power increase i cant give you a number but your smile when its done will tell it all. You will need to add as much as u can to the motor when you do this, go with a good cam for the money get yourself an xr400 cam. You should be able to do the whole thing for around 300$ take in mind that most piston manufactures give there compression ratios based on the xr400 not the 400ex so to get the advertised ratio you will need to run the xr400 head gasket, i would also order a gasket kit A for all the little gaskets you need along with the XR 400 Head Gasket. I did all the work myself and found it to be really easy if you have service manual. I would recommend your setup to be 416 with the XR cam, with the XR head gasket, 11:1 is the max you can run with pump gas 93 (Good Gas) I run a 50/50 mix with race gas. A good exhaust will help a lot to. Hind Sight is always 20/20 I would always suggest suspension first. J Make sure you get some type of intake mods done with the K&N or UNI, Get a good full system and your all set. The Hictrick pipe is really appealing for the money.

A 10.8:1 piston will run perfect on 93 octane never have to mix or run race gas. You'll love the setup no doubt,,,get the complete kit from marcums ATV,,just tell him your a new member on exriders.com and you want the hot 416 setup everyone's been gettin,,he'll know what ya mean..good luck.:D

How much bore is with the JE 416 kit. Do you get all the gaskets? Do you have to bore the sleeve or the cylinder? How will it run without the XR cam. I don't have enough for it right know and already have the engine tore apart. Will I have to rejet, and what size jets? How reliable are the JE kits?

When ordering the kit from marcums,,you'll get the piston and all gaskets. The cylinder will be bored .080 and I have to recommend the cam while your doin it,,,upping the cylinder size will help but you'll get more power with the cam. I had to rejet but only had to go up one size on my main jet,,,that's all..reliable I think so...:D I'm tellin ya go borrow the money or something to get the cam with this,,,well worth it.

[Holty]

i just answered all these questions for you in your last post just a couple days ago.
why are you posting basically the same thing again?


http://forums.exriders.com/showthread.php?s=&threadid=7631