High comp piston and cam?

[ChEX]

Alright, I want to know how much of a difference it is going to make. I have swapped engines in plenty of cars and stuff like that, but never any builing of engines. How hard is the install? How much is it going to run me? And what are some of the products to get?

[quadman]

for me , doing a piston and cam swap is easy just refer to your 400ex manual for directions,yes you will feel a difference and if you get a wiseco 11.1 comp piston and hotcams stage 2 it will cost a total of around 260 with shipping

[Dave400ex]

Yeah you will feel a difference with the Piston and Cam. What kind of riding do you do? There are many different Cams out there to choose from for your style.

[ChEX]

Most of my riding will be done on the dunes. I have paddles, and am going to get a silencer, k&n kit, and hopefully the piston and cam. Will I be able to run with Raptors and Banshees?

[433rd]

Originally posted by ChEX
Most of my riding will be done on the dunes. I have paddles, and am going to get a silencer, k&n kit, and hopefully the piston and cam. Will I be able to run with Raptors and Banshees?

Raptors most likely "Yes", Banshee's, a definite "No".

It takes a major pile of mods (and money) on the 'ol EX before you will be able to equil or surpass the downline speed and acceleration of the Banshee in the dunes.

The Raptor on the other hand is a much more realistic task and can be done with a few "strategic" mods to the 400EX.

[GoLikeHell]

Hi Chex,
Piston swap (11-1 standard bore) and a good cam can really wake your bike up. You might of already seen my post "just got off the Dyno" shows figures from a real Dyno Run. look at the powerband and see if that is what your looking for. I run a stage 2 hotcams and I love it, the damn thing will pull all the way to the limiter. Do not get the data mixed up with other peoples Opinions. Look at the rpms and see if that is right for you.

Good luck in trying to pickout a good cam

Mark

is ther a big performance difference from a stock bore 11:1 and a .80 (416) bore with the same cam?

[Matt Fisher]

When I bought my 400 it had a GtThunder 12.5:1 stock bore piston, GTT cam (Web 450/451), and a WBros slip-on. It was really quick, but needed race fuel.

I swapped the piston out for an 11:1 440, changed to a full-length WB exhaust, ported the head, and it "feels" like it has about the same amount of power.

I went riding last night with 2 Raptors, they certainly weren't pulling me, though we weren't drag racing either.

I'll sell the 12.5:1 piston if anyone's interested...

[ChEX]

How much does it cost to get the head ported and polished?
Rough ball park. This may be a stupid question, but what are the possibilties of me doing the porting and polishing myself?

[Matt Fisher]

Depends on how radical you want the porting to be, and how good (read: $) the porter is.

The more compression you're running and larger the displacement, the more you'll benifit from port work.

You should be looking at somewhere between $75 and $300 to have the head ported. To do it yourself you'll need bits made for aluminum, and a Dremel (though air tools are much better). I priced the bits at about $100, so spending $150 to have a local guy with lots of experience do it was a no-brainer.

If you don't know what you're doing, I'd suggest against it. Nothing wrong with learning, but I'd start with something easy, like a small block Ford/Chevy head. There are lots of books on porting, might be a good start.

The cheapest/easiest I've found to go fast was the 12.5:1 piston, Web cam, and slip-on exhaust. Only down-side is the need for race fuel.

[Dave400ex]

So your saying the stock bore 12.5:1 is just as fast as your 11:1 440?

[Matt Fisher]

I'm saying that I didn't feel any incredible difference.

A couple of important points though;
1) The race fuel/12.5:1 was fully broken in and jetted properly. My 440 isn't yet.
2) It's been about 4 months since I rode the bike, and last time it was in a more "open" area, so I was able to get on it more. There's no way I could draw a really accurate conclusion due to this.

What I am saying it that "bang for the buck", the simple combo using the 12.5:1 piston is tough to beat. Matter of fact, I'd say that for the 400EX, it can't be beat for the money/time.

That last statement ought to stir up the pot some... :devil

[Chef]

Originally posted by Matt Fisher

That last statement ought to stir up the pot some... :devil

Yep, I bet it does!

[Dave400ex]

Hmmmm. I wonder how a 12.5:1 416 Piston would be? That may be a hot setup. Will that high Compression cause any problems such as heat, starting, or reliability? I think maybe a 11.5:1 custom piston would be good.

[Matt Fisher]

Well, a 416 is 5% bigger than a 397cc motor, so figure about 5% more power- less than 2 horse. A 440 should provide you with apx. 10% more power than a similar 400. A 12.5:1 stock bore should make more power than an 11.5:1 416, IMO. If you're running race fuel, you're giving up some power for no reason.

BTW- I spoke to GTT before pulling the 12.5:1 and going to the 440. They said that I'd make a little more low-end, but there would not be any real significant power differences.

The advantage of a stock bore is the ease. Drop it in, no machine work needed. Heck, you could go from a stock 25 hp bike to a 35+ hp bike in about 4 hours, with no machine work.

Durability issue? Well, you are increasing the power by about 40%, so that ought to tell you something. Overheating? Race fuel will help keep that in check, but I'd still be seriously considering some additional cooling. Starting issues? Mine still starts great on the original 1999 battery.

[Dave400ex]

I'm not sure what to do. I may just get the 416 10.8:1 and be done with it. I know the higher Compression would be better, but I don't like the idea of going that high on what will be almost a stock motor.

[Matt Fisher]

Think of it this way-
How many people drop 440 kits and/or rev boxes in their otherwise stock 400EX's? RPM's are harder on motors than compression (to a point), and a 440 should make a little more power than the 12.5:1 stock bore (and more power equals more wear). So a stock bore 12.5:1 shouldn't be a problem.

You can decide right away if race fuel only isn't an option for you. If you're unwilling (as I was) to only run race fuel in your EX, then just forget the 12.5:1 and be happy with about 11:1.

You mentioned an almost stock motor. I wouldn't even consider running the 12.5:1 piston unless you also had a healthy aftermarket cam, vented airbox, and muffler. It would be unable to breathe.

[Drtridr18]

What do you think about Ross Pistons, was on their website a while ago, guess they are pretty light compared to others?

[Matt Fisher]

I must like them, there's a Ross in my bike now.

I'd have to preface that with saying that I don't dislike the JE's and Wiseco's. They all make good products. As I understand it, there are some off-brand cast pistons out there, those I'd avoid like a Janet Reno convention.

Honda Jim designed the JE and Ross pistons (he currently works at Ross), so there isn't any huge difference between the two. I was able to have some machine work done by Ross to lighten the piston, though I had to order 4 of them. In hindsight, I'd have skipped that machine work. I would however, use their lightweight alloy wrist pin again. It's only about $20.

The flat top of the Wiseco 89mm might seem like a disadvantage at first, but if you're decking the cylinder to reduce the squish, it might actually be a better piston to start with. This is assuming you want a pump gas friendly motor.

Oh yeah, the whole idea that a 20 gram difference in piston weight will make a huge difference in power and throttle response is silly. While it's better to have a lighter piston, it's not worth it to possess over it (like I did).

I believe that Thumper Racing
http://www.thumper-racing.net/trx400ex.html
has Wiseco pistons that have extensive machining already done to them. Might be worth looking into.

[Sick0]

I heard the connecting rod can't handle a higher compression piston like the 12.5 to1 piston.

[bmw500hp]

Originally posted by WarriorMan
I'm not sure what to do. I may just get the 416 10.8:1 and be done with it. I know the higher Compression would be better, but I don't like the idea of going that high on what will be almost a stock motor.

WM....Talk to Papaw.... he stepped-up from 11:1 and has some intersting things to say...May be the answer???

[bmw500hp]

Originally posted by Sick0
I heard the connecting rod can't handle a higher compression piston like the 12.5 to1 piston.

I heard exactly the same,,,and get a different answer every friggin time.... ????

[Sick0]

Well I'm going with 10.8 to 1. You don't have to run race gas or worry about the connecting rod. Plus you will still get a nice profromacne gain.

[Dave400ex]

Well I will be getting a TC XC Cam, and already have the TC pipe with soon to be a No-Toil filter, but the airbox is stock and staying that way. Race Gas isn't that big of an issue, but I have also heard it's not good to run 12.5:1 on a stock rod. I just want a simple motor upgrade. Piston and Cam is about all I will be getting. If I had the money, and may do it some day, I would do a 12.5:1 piston, rod, valve springs, rockers, cam, carb, and more. Also with just a 416 or 425 Piston, Cam, and a Pipe will my stock clutch be alright?

[Drtridr18]

I was thinking the 11:1 route myself, or max 12:1, but race gas on a bike I ride a lot, i'd feel kinda silly if I ran outta race gas and coulnt' ride with my friends at any time ya know?

[GoLikeHell]

Originally posted by WarriorMan
Well I will be getting a TC XC Cam, and already have the TC pipe with soon to be a No-Toil filter, but the airbox is stock and staying that way. Race Gas isn't that big of an issue, but I have also heard it's not good to run 12.5:1 on a stock rod. I just want a simple motor upgrade. Piston and Cam is about all I will be getting. If I had the money, and may do it some day, I would do a 12.5:1 piston, rod, valve springs, rockers, cam, carb, and more. Also with just a 416 or 425 Piston, Cam, and a Pipe will my stock clutch be alright?

11-1 comp on a stock bore is plenty of a power gain when you add a good cam. 425 puts the cylinder right to the max bore, so if you have any probs in the future your looking into a new sleeve.

With using a stoke bore High comp piston you save on machining the cylinder, plus you keep as much metal on the cylinders for overbores when you really need it. I just did a 11-1 425 kit and was surprised just how thin the walls really are. I wouldnt advise it only if you have a 416 and it needs a overbore.

Spend the machining money on getting your bike tuned properly on a dyno with a/f samlping. I perfect running 400Ex will smoke a poor running anything.


JMO
Mark

[4TraxRider]

what octane fuel are you running with your 12.5:1 piston? Can you run 93 octane and an octane booster instead?

[Dave400ex]

I think I will just get a JE 416 piston 10.8:1 like most of they guys on here run, but I will get the TC Cam. I may just go ahead and run 104 in it too so it will run better, and cooler.