I want to get an 11:1 piston, a cam and heavy valve springs.
Do I need to get it bored to put a new piston in?
What brands of these things do you recomend?
I don't have the $1,000+ to get a big bore kit.
And I want to know if this way is any cheaper.

Thanks for your help.

 

No, you don't have to get it bored. The piston will just slide right on in. A bore is only $35-$50 so I would recommend going .80 over, which would make it a 416. If you get the right cam you wouldn't need different springs, I would check out GT Thunders cam I have heard good things about it. You could either get a Wiseco piston or a JE piston. I have heard JE is better, but I think the highest you could get the JE in is 10:8:1 compression. I hope I helped you out.

 

I forgot, what is the stock piston compression ratio for the 400EX?

 

Stock compression is 9.1:1

 

I think that you can can just drop in the 11:1 piston in and you do not need to go to 80 over from stock. Why waste all of you overbores if you are trying to say money. Know the next time that you have to bore you will have to sleeve the cyclinder. Also, when you overbore the shop will charge extra going past the next bore because of the time it takes to go over.
I would just brop in the high comprusion piston and a mild cam if you are on a low budget.

 

JE makes pistons for 400's up to 13:1, now thats a squeeze!!!

 

If your on a budget, i'd say go for an 11:1 drop-in piston. I can't see gaining very much more power just by boring out the cylinder a little over stock. High compression is where your going to gain your power. I put in a lightened Ross Racing piston(C.T. Racing), and a Web-Cam 450/451 drop in cam along with my DMC pipe and K@N filter without airbox lid. My 400ex is considerably faster now. Try it.

 

You can also use an XR400 head gasket to gain another quarter of a point of compression. I did this when i put in my piston. So my final compression ratio is around 11.25:1. I run on pump premium still with no problems at all.

 

thanks for all the replies
Now where do I find these parts? Magazines, web sites or at my friendly local Honda dealer?

 

try recreationunlimited.com they sell a wiseco piston(10 or 11/1) with gaskets for $99.99 with free shipping over $100. i think i also got my white bros. cam from them for around $160.