Thinking about hoppin' up the old 400 with a 440 kit from White Bros, and their big cam. They have a choice of kits, one with a 10.3:1 piston, and another with a 11:1 compression ratio. I would rather run plain old gas still, super unleaded at 92 octane o.k., and I'm wondering if the 11:1 will be too much....maybe it will ping unless I add octane booster?

Also, the local dealer states that if they do all the work, it will still be covered under my 4 year extended warranty :-), but it's almost $400 in parts including new jug sleeve, and about $400 in labor. I'm wondering if I'll see that $800 in performance gains.....??? I'm already running the White Bros "e" series pipe, and it seems to do pretty good, especially with the stock aibox lid off. With that alone I had to jet up from the stock 142 to 162.

The bottom line is that right now it will BARELY pull second gear up a dune hill known as the "China Wall" at the Yuma Buttercup dunes. I wonder if I can get it to pull 3rd?

I need all the help I can get as I'm 6'2" at 255 pounds :-(.

 

I ride mostly in the Oregon Dunes and I did the IMS 440 kit from White Bros. and the all-around cam. I can definetly tell a huge difference especially on the low end, this thing has loads of torque! It does however vibrate a bit more than my buddy's stock 400EX, I notice it a lot in the wet sand and not too much in dry soft sand. We were riding the beach in fifth gear and ended up pinning the throttles and I just pulled ahead by a bike length or so before we let off. I was surprised that I didn't gain as much on top as I would have expected, then we drag raced from a dead stop and by fifth gear I had blown his doors off because it adds so much to the low end power and acceleration. I have talked to my local shop and Arlan from LRD specialties and they both said I am not getting close to the motors full potential without a much bigger carb, like 39 or 41mm, so count on that, I am saving for one right now! Also on the WB cam if you want more top speed I suggest the track cam, but for riding everywhere and hillclimbing the all around is probably better, the track cam likes to stay revved up more. I can climb any hill in 3rd and some in 4th!
I think I wrote a book!! let me known if you have any more questions
Later, Norm

 

Thanks Norm. What compression ratio piston did you go with? I understand they have multiple choices: 10.3:1, 11:1, 12.5:1. They state that you MAY have to run alternative fuel (hop up the octane) if you go with the 11:1 or higher. I still want to run super unleaded gas though. Maybe if I HAD to I would run a little 104+ octane booster that you can get from your local automotive parts store.

 

I'm also looking into kits,I seemed to have pushed the stock set up as far as it will go.
LRD header and pipe.
Dyno jetted- Third notch, Drilled pilot from 38-42, main jet 170, And holes in the airbox.

Norm, How much did your kit cost?
Did they do any head work,Biger valves? Porting?

I seem to be leaning towards a 440 bore and stroker kit.About $3100 and includes all the little toys.Carb,Porting,valves,springs,cam,rod, piston,Yada-yada-yada.

I was told it would put me around 52-54 hp. And boat loads of tourque.

Has anybody seen a stroked 440 yet?
I wonder how long it would last,HEAT!!?

norm-Bullseye about the carb.I just can't seem to stuff any more air/fuel through that 400.

 

By the way,"Dam" That curs'ed yz400f motor.Why couldn't Honda put that third intake valve in there.Now I have to drop a extra G just to keep up.

 

Hi guys, first of all, I went with the 10.3:1 just because I didn't want the trouble of going to a distributor to buy race gas, or having to order it, or having them be closed when I need fuel, where gas stations are open all the time. Any higher than 10.3 and you will have to run higher octane race gas. I actually tried running race gas and my 440 ran worse, it felt really flat(too high an octane). My best mix so far is a 92 octane with octane booster to bring it to around 98-99 octane, cheaper and easily accessible.

trx430ex, I have a K&N filter, airbox vents, and a Big Gun exhaust with header, when I did these mods I did the same carb mods, about as much as you can do with the stock carb which is smaller than a stock Warrior carb and we have 50cc's on that bike! I didn't do any head work, just bore and cam it cost about $750.00, I kind of wish I would have done the head work but I couldn't wait any longer to ride.
After riding the dunes my buddy and I cheked the oil temperature of our bikes, his is a stock 2k 400EX. We used a meat thermometer that read to 220deg, both bikes went well past that mark, I would say 250deg or so, his temp. actually went a little farther than my 440, I guess the temp. of the 440 isn't as big of an issue as I thought. I still wish someone would make a +1.5 quart oil tank to help keep it cooler(less heat=more hp). I stayed away from a stroker kit just because I want to stay close to stock reliability and I hear my IMS kit is damn close. If you guys are serious about doing it, I would suggest getting the carb first unless your doing a whole kit because it is a bolt on mod that adds HP to the stock bike but it is in place and ready when you want to go Big Bore!

About the YZ426f, Sure is a Badass motor, to bad Yamaha can't build a decent chassis to handle the power like Big Red can!!
By the way, how do you like the LRD system? I really like that pipe but it wasn't out when I bought my Big Gun.

See ya, norm.

 

O.K. guys. Since this larger carb seems to be the key, who offers it? What is the part number, website, etc. that I can find all the info on? Will it have an accelerator pump on it like the stock carb? I wonder how much it costs :-(

 

Oh yeah, one more thing I almost forgot. I've read about a really neat sounding oil temperature dipstick that replaces your stock on on the 400EX here in the forums. I believe it's from White Brothers, and runs about $45.00. Sounds like that's the ticket if you guys are really worried about heat.

I know my stock 400EX, with a White Brothers pipe and jetted from a 142 to 162 runs with cherry-red headpipes after climbing just one monsterous wall dune hill. Of course, it's more noticeable at night when you can see the "luminous" effect of those head pipes glowing in the dark....

 

i have a 400ex and am considering jetting the way it sounds i need it. i have a high flow air filter and am about to purchase a add-on exhaust. what are you opinions on this and how do i do it.

 

The best carb for the 400EX is a 39mm Keihin FCR. Same type of carb that is on the Yamaha YZ426 dirt bike. Call LRD Performance Specialties They will tell you all about it. They sell it for $429.00, kind of spendy but I hear it is well worth it. Here's their number (503)661-6700.