426 13:1 compression?

[Ryan02400ex]

I had my 400ex bored to a 426 about a year ago and I put a J.E. 11:1 piston in it, and replaced the gaskets and valve seals etc. It smoked blue like a two stroke before that and used oil like gas. I think my valve seals are starting to go again because its starting to smoke a tiny bit. So how reliable would a 13:1 426 be if I decided to throw a different piston in there too?

[Ryan02400ex]

Also thinking about putting a stage 3 hotcam in.

[ish416]

These engines run way too hot for 13:1 unless you have access to race fuel or something like 100LL. Also, at 13:1 you couldn't mix the gas to save money. The minimal power gain of 13:1 over something like 11:1 is simply not worth the added headache. I know this for a fact.

A stage 3 Hotcam focus' the power for the upper rpm range. In my opinion this defeats the purpose of owning a 400EX. A stage 2 Hotcam is about the best overall cam you can get. Great power everywhere with a bit more on top. Also, you would need to port the head and put on an 04-05 450R carb or step up to an FCR to get anything out of that cam.

[CJM]

Too much compression, if you dont have the heavy duty studs you will need them. Your also going to need to use 100 octane or better all the time. I wouldnt do it. HC3 is not worth it either, unless all you do is drag race a HC2 is a better overall cam.

You want 13:1 sell your 400 and buy a 450 and run race gas all the time.

[Ryan02400ex]

Alright thanks for the input guys

[2001400exrida]

The reason the stage 2 will be a better cam is because with the stage 3 is specifically designed for the hot rods big bore stroker kit. If you're planning on running a stroker kit, I wouldn't hesitate with the stage 3.

Just curious if any of the previous posters have run a stage 3 cam? I have never put one in my machine but i've ridden an MX 400ex that had the stage 3 and I don't care what you say, they aren't dogs through the lower RPM's. The stage 3 is made to improve the higher rev power, but they don't sacrafice much in the other RPM's.

Lots of times people will just give their opinions based on what they read, but if you go out and talk to some guys with built 400ex's, quite often you will learn the opposite of what you might read on the forums. The stage 3 is not a drag only cam, it's a good cam that improves higher rev power without sacraficing too much lower power.

[chronicsmoke]

I had my 400ex bored to a 426 about a year ago and I put a J.E. 11:1 piston in it, and replaced the gaskets and valve seals etc. It smoked blue like a two stroke before that and used oil like gas. I think my valve seals are starting to go again because its starting to smoke a tiny bit. So how reliable would a 13:1 426 be if I decided to throw a different piston in there too?

I agree with ish and CJM, at that point (full race fuel, HD studs, ect) you'd be better off with a stock is 450r on plain-jane 91 octane pump gas.

I'm runningm a 450r but also have a 426ex with a magnum stage 2 cam, 450r carb, full pipe and it's not a slouch at all. Keeping in mind I lose to stock-ish yfz450s with this setup down the straights and in a drag. Out of corners it's an animal though.

I'd get a 450r carb and add that your setup. If you are taking the head off to look at the valves maybe have a cheap rec. port job done to the head while you're in there, there is some power to be had there as well.

Have fun with it, if you're trying to whoop up on 450s, save your money and buy a 450. If you just want a strong reliable trail warrior, keep it on pump gas and put your money towards a carb and St.2 hot cam. Those two mods will put the biggest smile on your face! You're barely using that 426s potential if you still have the stock cam in there

[ish416]

The reason the stage 2 will be a better cam is because with the stage 3 is specifically designed for the hot rods big bore stroker kit. If you're planning on running a stroker kit, I wouldn't hesitate with the stage 3.

Just curious if any of the previous posters have run a stage 3 cam? I have never put one in my machine but i've ridden an MX 400ex that had the stage 3 and I don't care what you say, they aren't dogs through the lower RPM's. The stage 3 is made to improve the higher rev power, but they don't sacrafice much in the other RPM's.

Lots of times people will just give their opinions based on what they read, but if you go out and talk to some guys with built 400ex's, quite often you will learn the opposite of what you might read on the forums. The stage 3 is not a drag only cam, it's a good cam that improves higher rev power without sacraficing too much lower power.

I have ridden many 400EX's and a few that were strokers and some with the stg 3 hotcam. If you like riding your EX between 7,500 - 10,100+ RPM (with aftermarket CDI) then go ahead and get a stage 3 hotcam. I personally prefer to use the mid range of my EX vs nearly floating the valves to go fast.

The Stg 3 hotcam doesn't kill the low end but there is a noticeable loss versus a stock to stg 2 hotcam. Also, the higher RPMs aren't much better than the stg 2, it just carries that power a little farther out in the RPM range, assuming you have the top end mods to support it.

[2001400exrida]

The 400ex's that i see ruling the flat track series in my area, i know that 2 of them (one guy i know personally) run the stage 3 cams and they get more power on top and hardly lose any on bottom. If you're machine is setup properly for the stage 3 cam you can certainly benefit. Now for trails and what not, sure a stage 2 is going to have all the useable power that you might need, but it will start to drop off when you get past 7k rpm's, whereas with the stage 3 you're power is still gaining at that rpm.

it's all preference, but to say the stage 3 is only a drag cam is not true.

[atvrider13]

I went from a stage 2 hc to a stage 3. Didnt notice much difference maybe a lil more on top, but im running a 41mm fcr. That carb really made mine rip.

[Ryan02400ex]

Alright thanks guys, I think I will just put a stage 2 in. Should I do anything new with the valves while I'm in there?