I will soon be getting a 400ex as a back up quad for racing. I will put elka shocks on it. And i plan on doing some engine mods I think I'm going to limit myself at 1500$ on the engine performance. I definately need a pipe and filter, What other mods are the best for my money.
440 High comp kit?
Quicksilver Carb?
ect..

 

I have had a few motors built for my 400ex. If you are wanting a backup bike and wanting some reliability, you need a 416 not a 440.
You need to keep the compression under 12-1. The smaller bore piston will rev better than the 440. I ran a 13-1 compression 440 all last season and blew it up every 2 months. I put everything off the top end(Curtis Sparks race cam, LRD ported head, heavy valve springs, hardened rockers,) on an 11-1 compression 416. It runs just as good but lacks a little off the bottom but it revs better, it is actually faster if you just drag race it. It is definately more reliable and also a cheaper motor to build.
As far as a pipe I would run either a Curtis Sparks or LRD. The LRD is actually made better and will last longer, it is also chrome, they run about the same though.
The FCR carb that everyone thinks is so great doesn't help enough to spend all that money, I have one and it is on the shelf with the stock carb on my bike.
The main things you need is a good cam and ported head. of course the pipe too. I hope I helped.

 

Hey,

I know a guy that just got a 440 and he said it was awsome I would go with that. Good choice on the Elka's they are cool.

 

well... sorry to offend you barlett, but the guy said he was buildinga 400 for a backup bike. The 416 runs cooler than the 440, it is cheaper to build and your right you won't know the difference between the two, so why would you spend the extra money to make the motor less reliable, and not run any better. I personally have both these motors in my garage right now. I am running the 416.
As far as my engine builder maybe you can tell Mr. Lehman of Lrd performance what he should do different. The truth is when you get 50 horsepower out of an air cooled motor made to put out 30 hp something is going to give. The motor problems consisted of throwing the stock rod through the case, splitting the sleeve, and then tearing up a Carillo rod. 3 time, every 2 months= 6 month season, get it.
I am simply stating spending the extra money on the 440 isn't worth the problems unless you are racing every weekend, which is what I was doing last year, now it is my back up bike and I still Get ythe same holeshots I used to get. The only difference is I can't lug the corners in 3rd. Also building an engine is not ALL about displacement, and the big boys, who are the big boys, the big boys don't run 400ex's do they?
I was just trying to help this guy out. I am not trying to sell anything, I have personally raced these things, I'll be at London, KY if anyone wants to see my bike or anything. sorry if I upset anyone.
Merrill Crose #12

 

Thanks man. I defineately want to run a reliable engine. And as for the big guys. I think i read someware they used a 416 kit for some baja race, I recall harold goodman and wes miller road it.

 

Does lrd make a 416 kit? Who shoul i go with? and what should the first things i get be? cam porting. obviously a pipe and filter first but what after that. and yes reliability should still be good. Thanks again

 

I wasn't trying to say they are faster than a 440 because they are not, truth is you get more bottom end from a 440 and more top from a 416, but you dont lose the bottom end power you think you would. I used to feel the same way. I spent $2500 building a 13-1 compression 440 with LRD, after the corrilla rod went out, I put an 11-1 416 piston and cylinder on it with all the other parts the same. I was really surprised with how well it ran. It does rev quicker, not so much just anyone would notice, but I noticed. I geared the front sprocket down from a 16 tooth to 15 tooth and I can ride it the same in the corners and still lauch in 2nd. I wouldn't believe it either, but I rode them both ways. If I was still racing it instead of the yzf I would run the 13-1 440 for motocross, but I would risk motor damage.
I would have a local dealer bore your cylinder and by a JE piston 11-1 .080 overbore. I would by a sparks race cam, heavy springs
and have the rockers hard faced. I think TC racing is actually the cheapest to have your head ported. Pipe LRD or Sparks X-6. Stock carb will work fine. This set up will be reliable and plenty fast. This is the setup of my 400 ex and I still get holeshots in the A class at local motocross events. good luck.