bore question

[Dumontexrider]

Im thinking about boring my ex to .120 over and i need to know if it uses the stock sleeve or not.

[Rico]

It uses the stock sleeve. I'd suggest an .080 over rather than .120.

[Dumontexrider]

why .080 instead of .120?

[Dumontexrider]

im also looking into getting a 440 kit instead but i have another question, whats the difference between 11:1 compression and 12:5:1? I got a 11:1 when i got .080 on my old 300 because i heard its better for your engine

[sportraxkid]

12:5:1 gives your more horsepower but is harder on the rod and head studs. You will need a hardend rod and bigger head studs if you go that route. I would recommend the 440 kit with the 11.1 ;) plus if you get a 11.1 you can run 92 octane so you can get it at any gas station. I didnt want to pay 8 dollars a gallon.

[MarkyNark]

Originally posted by Dumontexrider
im also looking into getting a 440 kit instead but i have another question, whats the difference between 11:1 compression and 12:5:1? I got a 11:1 when i got .080 on my old 300 because i heard its better for your engine

Dumont,

The higher the compression, the more horsepower you generate. There are only two (and only two) side effects. 1) The need for higher octane fuel to prevent pre-ignition, and 2) higher compression pistons are heavier - which makes the motor rev slower.

For dune riding, which is all I do by the way, 12:1 is very good. Its a good balance between rev quickness and horsepower. You can increase the rev quickness by also lightening the flywheel. You also need to be aware that if you run a 12:1 piston, you will need 110 octane fuel (race gas). Race gas is everywhere if you look, and its not that much more, about $1.50 per gallon, just a little more than premium gas. You can spend more for some types of race gas which are very expensive, like VP U4 - at about $5 per gallon.

As far as the Rod and head studs, I believe that if you have someone bore the cylinder correctly, you will not need a new rod for a 440 kit. If the bore not done correctly, and is off-center, it's incredibly hard on the stock rod. You will NOT need new head studs. If they are torqued correctly by a good mechanic that knows how much they need to be torqued by, you wont need new studs. Ive been running the stock studs and stock rod for a years worth of duning and dune drags - nearly every weekend - and I have had no problems.

A lot of shops will instill fear in you and will ask you to buy a new rod and new studs - Its more money for them, so thats why they say that. If they say you need them, run away and find someone that can bore a hole that center.

If you go with a 440, please get a decent cam and correct parts like valve springs and shortened valve guides like the cam manufacturer recommends.

Far too often idiots, which call themselves mechanics, dont even read or understand why they are needed. Web is very open and good about its recommendations without bias -

Further, to make your 440 work right, consider a decent carb and a full pipe.

There are several choices of good full pipes depending on your application. For duning, and the noise restrictions which are in place for many dune area, the LTE is simply the quietest performance pipe for the EX there is. Its high flow design with two mufflers makes it perfect for duners.

The FCR 39 is ok, but works with the 440. I've had that one. I recently purchased the Edelbrock 38 and I like it best.

[beerock]

most mechanics who know the 400ex motor reccomend new cylinder studs because of the fact that the stock cyl studs are pressed in and pull out. I wouldnt run from a mechanic who says that. I would actually notice that about the mechanic and it would show me he knows what hes doing. Although the studs are not needed unless you go with a high compression piston. yes it does cost alot mor ebecause you need the studs threaded for the casings. I feel if i owned a 400ex and did a low comp 440 I would get the studs because i would be revving it out alot and over time i feel the studs would pull out. Thats just how i ride though, if you dont keep it WOT all the time then you should be fine.

my .02cents

[MarkyNark]

You can get new cylinder studs if you want, in my opinion, after racing for a year with a 13:1 piston, - yes, at 13:1 piston! on the stock studs, they are simply not needed.

Beerock, this is no dis, just my opinion. A lot of guys get them and pay no attention to the other items such as shortend valve guides and stiffer valve springs which are way more important.

If it makes a rider feel better, then they should get them. but in the end they will make no difference longevity of your motor. They are not hugely expensive, and are simply charity to the mechanic that puts them in. There are alot of other ways to feel better!

If it wasnt, there would be no way that I could run a 13:1 piston for a year full of racing - I mean my cylinder should have shot off by now! HAHAHAHA! :eek2:

[beerock]

the head isnt the problem its the CYLINDER studs thats the problem.(unless you just got the word confused?)

But hey i understand its no diss im happy its workin for your motor. From what ive seen and heard at the honda dealer the cylinder studs do pull out with 440 kits. It could "possibly" be that the machined holes were slightly smaller(maybe the bit on the cnc needed to be changed?) who knows, im glad its workin for ya.

on another note, If i had a 440 ex i would do the valves, springs, cams etc as well as the threaded cyl studs;)

so it may work for some and not for others all i know is i would do them from what ive heard.