416cc build

[sprayedgt]

Starting to put together a list of what I need to do a 416 build on my '08 400EX. Since it's getting to be winter it'll be down for a while and I figure now is the time to do a project like this. I know a ton of you guys have done this, and I wanted input from the experts so I get it done right the first time. I'm looking for a big power gain here. I'm going to have the head ported, add a good cam, and of course an over bore. What all is needed so I can have everything ready to go? What piston/cam combo an compression is the best for a 416 build? Is it worth the money to port/polish the head? I mostly do aggresive trail riding with an occasional high speed lap or 2 around the oval and MX track. Thanks everyone.

[dariusld]

Since yours is a 2008, you don't have to go 416 to get the advantages of a 416, just any hi-comression piston will do. Maybe a stock bore or a 405(whatever it is).

[sprayedgt]

So I could use the stock bore but just get a 11:1 piston? Would I need a re hone of the cylinder or what? I have about 300 miles on it.

[dariusld]

Originally posted by sprayedgt
So I could use the stock bore but just get a 11:1 piston? Would I need a re hone of the cylinder or what? I have about 300 miles on it.

Yes, you can do stock bore11:1 as long as your cylinder is OK. But they say you need to hone it. You should save the overbore for when you need it.

[sprayedgt]

OK cool. That'll save some time and expense. So getting the head ported/polished, stage 2 cam and a 450R carb should be a very nice gain? Enough to keep up with the 450's?

[dariusld]

Originally posted by sprayedgt
OK cool. That'll save some time and expense. So getting the head ported/polished, stage 2 cam and a 450R carb should be a very nice gain? Enough to keep up with the 450's?

That is a nice combo. I had all that except the carb, then added it later. Everyone hypes the carb, but I'm not impressed with it. Some will also disagree with this, but I have a rev box also, and I think it compliments the revvy cam and heavy breathing and they are pretty cheap.


Sparks says not to run the key with this combo.

"Just not high compression or big bore pistons."

[Brauap]

Originally posted by dariusld
That is a nice combo. I had all that except the carb, then added it later. Everyone hypes the carb, but I'm not impressed with it. Some will also disagree with this, but I have a rev box also, and I think it compliments the revvy cam and heavy breathing and they are pretty cheap.


Sparks says not to run the key with this combo.

"Just not high compression or big bore pistons."

They consider 12.1 + high compression.. so I don't really know..

[sprayedgt]

Going to send the head off to Trinity Racing in CA for the stage IV port/polish job. He said they gaurantee 5hp just replacing the head, but will be about 8-10 with the stage 2 cam, 450 carb and 11:1 comp. I'm doing dyno runs before and after just to see where I stand.