11:1 400ex build help!

[dirtracer]

I havent found a definate answer yet. I'm building a 2000 400ex into 416 and need some pointers. I bought the bike cheap (blown up) and have a little money to put into the motor. I wanted to make it into a 416 because reliability is my main concern, but I don't want to run race gas through it. Shell's V-power 93 octane gas has been good to me in the past and I was wondering if I could run 11:1 compression on 93 without detonation or would I be better off to go with the 10:1 piston. I've heard that a 10:1 416 might as well be a stock 400. I have to replace the sleeve anyway so would it be better off to just make it back into a 10:1 400. I'm also at a loss for the cam and jetting setup. I've heard a lot of good about the 450r carb but if i go sticking too much money into this I would be better off just getting a 450r. OPEN TO ALL SUGGESTIONS. Thanks!!!!

[crownandmonster]

A 11:1 piston is actually going to get you somewhere around 10.5:1 compression with stock 400ex gaskets. I run an 11:1 with xr gaskets (supposed to make it a true 11:1) and it runs fine on 93. You shouldn't have any problems with it. 450 carb is a great idea I love mine. As far as a cam goes I went cheap and just got a hotcam. It is a good cam for the money, but they do not perform as well as something like a Webb cam would. In the next couple months I am going to be purchasing a Webb to replace my Stg. 2.

[ish416]

11:1 with XR400 gaskets should run fine on 93 unless it is seriously hot out (95+). On those days even a stock EX would start having issues with heat. If you plan on doing a high compression EX I would suggest an aftermarket oil cooler and a SPAL fan to keep it running at a decent temp.

I run Shell V-power 93 in most of my vehicles and it has proven to be a great fuel compared to other "premium gasolines".

As far as bore size, going to a stock cylinder will give you a few over bores on the stock sleeve (402, 406, 416, 426). If you plan on keeping the quad long term that decision is up to you. I noticed a major increase in torque going from a stock bore 10:1 with XR gaskets and a sparks timing key to a 12.5:1 416 with stock timing.

As far as cam selection, a stage 1 hotcam is basically the stock power with a bit more hit. A stage 2 is a little lazier off idle with more mid and top end. A stage 2 and an 11:1 416/426 have proven to be a great combo. Also the hot cams are just drop in whereas other cams require hard faced rockers. So there is something to think about on a budget.

Down to the carb. It really depends on what carb you are referring to. A great cheap upgrade is the stock 04-05 450R carb. It bolts straight up and adds about as much power as an exhaust and intake. It really does wake up the EX significantly. If you want to spend a bit more coin and the possibility of modding some things an FCR is about the best you can get.

The best bang for your dollar would be:
11:1 piston (JE or Wiseco only)
stage 2 Hotcam
04-05 450R carb with jets
A cleanup port job on the head
larger oil cooler and/or spal fan
*Almost forgot a very important part. HD Head studs for any size high compression EX.
OEM XR400R or Cometic gaskets

Those combined should net you an easy 6 - 8 hp gain over a stock EX while retaining reliability and ride-ability. With these mods you should be able to keep up with a stock 450 for less than $500 - $800 depending on where you gets parts from and who is doing the work.

If it wasn't a proven setup then 2/3 of the members here wouldn't have built one with very similar specs.

Just don't ever ask about replacing the CDI with a rev box as it is a complete waste of cash. Also, a full exhaust is not needed. Just a slip-on should be fine without it becoming a factor.

[DragonGunner]

Originally posted by crownandmonster
A 11:1 piston is actually going to get you somewhere around 10.5:1 compression with stock 400ex gaskets. I run an 11:1 with xr gaskets (supposed to make it a true 11:1) and it runs fine on 93. You shouldn't have any problems with it. 450 carb is a great idea I love mine. As far as a cam goes I went cheap and just got a hotcam. It is a good cam for the money, but they do not perform as well as something like a Webb cam would. In the next couple months I am going to be purchasing a Webb to replace my Stg. 2.

You could get a JE piston 10.8:1 an be allright on 93 as well...I had one in 416 an loved it.

If you go Webb Cam you'll want to spend the $ on hard surface rockers....the stocks are chrome coated an will wear out quick with the Webb cam....I have a Webb an I went with the Hardened rockers....Hotcam hadn't came out yet....today i would try a Hotcam an not worry about the rockers.

[DragonGunner]

ish416

Just don't ever ask about replacing the CDI with a rev box as it is a complete waste of cash.

Unless its a White Brothers CDI an your racing....fixed it for ya fellow Hoosier.

[dxcody]

11:1 on 93 pump will work fine.

stage 2 hotcam is what i would do. I know it says mid-top but with my setup i still have a boatload of torque and it pulls awesome in every gear. Its still just as snappy taking off in 1st as a basic 400, so the way i look at the stage 2 is that your not really losing any low end, your just not gaining any low end either.

i havent ran the bigger carb yet, but i heard it helps alot.

Just like ish416 said, you might as well go stock bore and 11:1 (or whatever piston style you choose)

Your power gain doesnt really come from the extra millimeters a bore gives you, its all about the piston you put in for the compression and the cam to match it. That way (like ish416 said) when that bore wears out, you can bore it to a 406, then a 416, then a 426.

GT Thunder HD head studs are great, as long as they are installed right, and they provide a little more insurance to your motor.

But if you are dead set on a 416, then in the future when you have to rebuild it you dont really have to replace the piston, just replace the rings and buy a new sleeve and have it board to match your piston, since pistons dont really go bad.

Just what i think. If i had my way mine would be a 416 instead of a 426 but it was already a 426 when i bought it.