difference between stroker and 440

[400EXracer74]

whats the difference between a stroker kit and a big bore kit. Whats the power difference?, whats the cost difference?, which is better in your opinion. whats the difference on the installation. also how does either compare to the yfz? I have a honda 400 ex and am looking into makign the engine a lot more powerful. and i have the money to do it right.

[TM426]

With a stroker the connecting rod has to be changed and the cases have to be split and machined. With a stoker you get more displacement which = more power and the sleeve is bored out. There is alot more cost in doing a stroker compared to just a big bore. As far as a power I have never riden a stroked 400. I know the power numbers are close to a piped 450.

[BLEEDRED]

I don't know much about it but I can tell you that a stroker kit moves the rod farther out on the crank and involves splitting your cases. A stroker would be much more costly than just boring/sleeving the top end. Good luck!

[BLEEDRED]

With a stroker the connecting rod has to be changed and the cases have to be split and machined. With a stoker you get more displacement which = more power and the sleeve is bored out. There is alot more cost in doing a stroker compared to just a big bore. As far as a power I have never riden a stroked 400. I know the power numbers are close to a piped 450.

Darn, you beat me to it...we must have posted at the same time...:rolleyes:

[400EXracer74]

which gives more power and reliability. i have heard bad things about 440s but i havent really heard anythign about stroker kits

[TM426]

I think personally the 440 is more reliable (less motor work). A stoker is a 440 (depending on what kit) plus the machining. So either way you are getting the sleeve bored. If you get the 440 I would suggest larger head studs.

[BLEEDRED]

My 440 rocked out until the head studs started pulling out, I thought. As it truns out is was the three 8MM head cover bolts on the cam chain side that were stripped which was causing oil to blow out the head gasket. So it's torn apart right now to be made right with FDO heavy duty head studs and inserts for the 8MM head cover bolts. Jeff and Extreme Tec-ATV in Ohio is taking care of me.

Other than that this thing has been reliable and I did all the work myself. I can say that it tends to run hot in the summer. So if you are planning on riding in the heat of summer or do a lot of dune riding you might look into a oversized oil tank...

[400EXracer74]

ill just learn from your mistake and put in larger stronger bolts the firts time.

[promisc]

From my understanding... (correct me if im wrong)

As equal cc, a stroker deliver more torque, a big bore deliver more power. With a longer displacement, a stroker will apply a bigger force on the crank (like using a longer wrench to torque a nut) but it will not rev as quick as the big bore. Thats why we say that the 450R is more torquy and the YFZ rev more quickly. They dont have the same displacement. So use a stroker for slow and difficult ride like wood, hill/dune climbing and big bore for fast tracks, racing...


For the cost, a stroker mod is definitely more expensive.

[ghak99]

You might do a search and find the information your are looking for.

I prefer a combination of both motors, but big bores are cheap and easy. The power output between the two is a little different. As a general rule of thumb, a stroker will put out more torque lower in the rpm range and rev slower than a big bore motor. A big bore motor will rev faster and higher.

I find a stroked motor more suitable to my riding style, useable power that comes on strong everywhere in the rpm range.

[400nate]

i know this tread was last posted in march...but just thought i would put my input in...i have been running a 440 stroker kit now for 2 yrs.....i didnt machine anything inside the case.....also running 11:1 comp...never had any of my studs pull...i'm still running the stock rod...not a single problem at all....except a cam bearing failure..wich i cout while fixing a leaking valve cover gasket.......in my opinion..the stroker kit 416 +4mm stoker revs fast and powerfull......i have yet to find a set of tires that can stay hooked to the ground in 5th gear...so in my opionin the 440 stroker is way better than the 440 big bore..cuz the piston is lighter and provides way more torque....i got my kit from powroll still very happy..friendly people...they answer any questions...

[bwamos]

Originally posted by 400EXracer74
which gives more power and reliability. i have heard bad things about 440s but i havent really heard anythign about stroker kits

A big bore is a little more reliable, much cheaper, and will rev faster.

A stroker will give you more torque and low end power, but will be little slower revving and little less reliable. Less reliable (moreso higher wear) because the stroke on the crankshaft is increased so when the crank is at it's farthest left or right points it has a larger angle pushing the piston up against the sleeve harder.

Most people avoid strokers. They are expensive (because you have to replace the crankshaft) and less reliable. But you do get a lot of power out of the Big Bore / Stroker combo. So they are used in some race applications.

A stock 400ex has a 70mm stroke.
As well a stock 450r has a 64.8mm stroke.

They are both right in the bottom of middle ground as far as standard 4-stroke engine strokes go. Stroking either of these shouldnt really be much of an issue.

The Rubicon is even running a 75mm stroke.

Edit: bah got sucked into a 2 month old thread.. lol.

[400nate]

i dunno..i still dont agree about reliablility.......everytime i read a post about 440 kit...people are complaining about pulling studs...

also with the stroker your not thinning out the aluminum to make room for the big sleeve....wich could possibly weaken it.....but still i think it would all come down to prefrence...

for me i like strokers...lol...when it comes time to do the kfx400 i will drop a stroker kit in it...

so i guess its either monster torue...or maybe alittle fast rev...i rather take the torque over rev any day..cuz a stroker will be in the next gear pulling away while the bigbore is trying to rev out to get the power it needs for the next gear....

like when i drag race...i go 1st rev maybe halfway then to 2nd for about 15 feet then right to 3rd and let it rev..and finish out the gears...this meathod keeps the front down and still pull hard...