Stroking the 400ex

[nakomis0]

What all is involved in stroking a 400ex motor?

Is it a Longer rod.
longer cam chain.
different crank?

What else do you need?

Could I just stroke my 440, and make it a 473?

What the pros/ and cons of this. (lose lowend, reliabilty, ect)

Feel free to take your time with your answers, cause I really would like to know the facts and all thats involved. Tnx.

[nakomis0]

I did some quick searching and it looks like most guys with 440's are using a 74mm stroke. That would make it a 460.

460, 473, whatever :)

[250xman]

the only thing with stroking is that you lose some of your top end. if you think about it it all makes sense. it makes the crank longer so it gears it down some. so if you do stroke it i would recomend putting a smaller rear sprocket on.

[ChadEXer]

Dont hold me to this but Ive heard that stroked gives you more power than the bore, so basically a 465(a 93mm piston I think) wont give you as much power as a 460,472 whatever stroked. Not sure but seems like I heard that.
Tom is stroking mine 6mm which is 76mm with a 92mm piston makes it a 505.

[nakomis0]

Anyone have a guess on how much extra Hp a 74 or 76mm stroke might give?

[Wheelie]

Chances are, with a stroker crankshaft, either a shorter than stock rod would be used (not necessarily a good thing), or a modified piston with the wrist pin moved up.

The cam chain isn't affected. IMO I would go with the 4mm stroker for maximum reliability and less of a chance of the cases needing machine work.

PROS--More power and the ability to accept a more aggressive cam than a stock stroked engine.

CONS--RPM range will move down slightly, lose some reliability, cost.

Just a wild guess---10%--15% power gain, and substantial torque gains.

Later,
Jeremiah

[440exnacsracer]

im lookin for a stroke kit for my 440. i do know this though. stroke adds more hp than big bore. think about it, it gets more leverage on the crankshaft. it also is better to be lugged in lower rpms than stock. if you get a large stroke rod and crankshaft put on, it is less reliable at high rpms because of the stress, but the substantial hp gain at the low end can make it a killer mx and cross country machine. i would leave the stock rev limiter on if i got a long stroke rod too... increase reliability.

[Chris400extreme]

i just got my 500ex kit back from m Dunlap so i will tell you guys about it later this week if everything goes right. you are supposed to be able to get monster gains out of this moter or the tc 505. i am going to be on race gas for a couple of months then probably swtich to alcohol later on. i am hoping to catch a match race with my sleeper bike against a new Z400 and then tell him it is all stock. HEHEHEHE. post some results later in the week

I have riden a 463, 473, and 460. If you already have a 440 kit that rules out the 463. All have great usable power. These kits are excellent for woods they provide enough power throughout all rpm's that you very seldomly have to down shift. The 460 is 4mm stroke and the 473 is a 6mm stroke. I know that For Dirt Only who does all of my work uses a stock length rod and a custom JE piston with the wist pin moved. The first thing you will notice with these motors is that they do not rev very fast at all. The 460 does rev a little faster. I know people who run both of these motors in the GNCC's and have had no problem with reliability. The number one expense in haveing it done is basicly splitting the case. I am not positive on these prices but they are close: 350 split case 300 stroke crank 175 new rod 195 new piston and rings. Stroker kits do take some time to be installed so if it something you want done by a certain time you should jump on it right away. If yoiu want to give Mike @ FDO a call he can give you more info and better pricing he builds alot of big bore and stroker motors (740)967-1078