I need to know what cam piston size and what pipe works best with the 416 kit. I know this is all guessing game but at least I can get some input. Thats what this forum is for anyway. I like the hp2 DG system and the BIG GUN all the rest are way to expensive for the gain you get. Also jetting for the OK area for these mods and I already have K&N but will be removing air box lid. not much mudding for me that is what the polaris is for.hehe

 

The compression ratio you use will largely affect your cam choice, as well as the exhaust system.

The big gun is known for killing top end, not a good choice for a wild cam. DG is notorious for making less than par products.

I run the 87mm piston @ 10.8:1 with an XR400 cam, ported head, and stock exhaust. This setup works well, the bike is a sleeper, although not as fast in a drag race as a more heavily modded bike, it's throttle response is much improved over stock and has more overrev. For less than the price of a complete exhaust, I got substantially more performance than simply bolting on a pipe would provide, without the noise.

 

Do not get either of those pipes. I have a big gun and when you build you engine, they are really restrictive and cannot flow. I would suggest keeping your stock headers and getting a yoshi, or DMC slip on, you will have more power that way, I am ordering a different pipe because my big gun is restricting my power, I will probably get a White bros. pro meg or a DMC.
Now I would go with a Web cam 450/451 grind or a mx grind cam and either 10:8:1 or 11:1 compression. I have heard with the 11:1 you have to run half pump and half race, but when I get my 11:1 426 piston, I will run 92 octane with some octane boost.

 

Get the DMC pipe. With all my mods, I can outrun piped Banshees

 

My 400 is a 416 with a JE piston 12:1 compression. This is for motocross though. For trail riding/recreational whatever, I would run 11:1. You can run 92 octane with an 11:1 I know that for a fact. For the pipe I have a Curtis Sparks X-4 which BY FAR flows way more than any other pipe I've ever seen. Just idling it stirs up dust when the air hits the ground. It sounds great too.

 

What mods do you have, and recommend.

 

I have a Ross lightened 11:1 piston(stock bore size)XR400 head gasket for a total of around 11.25:1 compression, Web-Cam 450/451 grind cam, DMC full exhaust, K@N filter without the entire airbox, W.B rev box, and a Lectron carb that hasn't impressed me yet. I safely run 92 octane gas, but throw in some octane booster into each tankful just to be safe.

 

If you are going with the 416cc kit because of the size limit in the 400cc class limit, it has been changed to 440cc for the coming year. A 440cc kit will be legal next year.

 

GABE:

I bet if you put a Curtis Sparks on your bike, you'd have sick power gains!