Stroker vs. Bore

[redexrider4290]

I was looking at 470 kits for my 04 450R and i have found 470 bore kits and 470 stroker kits the stroker kits have been cheaper but i was wandering what the differences are.

The stroker kit says it uses the stock piston and I understand it increases displacement by lengthening the stroke but how do the 2 differ in power and performance.

how do the 2 motors differ in how much power they produce and where the power is, how fast they rev, how high, just everything what are the differences

thanks

[trailwart]

i dont know what kind of power your looking for but my buddy had a 480 kit in his 04 and a ported head and bored carb and i would hand him his ***, didnt matter who was on his quad i still beat it. it wasnt what he expected and now he is planning on going bigger to a 500 sumthin stroker big bore. another buddy has an 06 thats ported and its a better performer than the 480 was. just do your research to make sure your gonna get what you expect.

this what i was on


http://i203.photobucket.com/albums/aa217/trailwart/100_1391.jpg

[deathman53]

basically, NOT ALL THE TIME. A stroker makes more mid-top end, while a big bore makes more torque. Of course the cam, carb, air intake and pipe have an effect on this too. That really is a question for the person whom is selling you the bore/stroker kit. Keep in mind a stroker kit involved rebuilding the bottom end and buying a stroker crank or having yours modified. A big bore usually involves buy a bigger cylinder or having yours put a new sleave in.

[kawiefan]

if your looking for more bottom end grunt a stroker will produce more low end as well a hi comp piston. also a more back pressure will make more low end.

[gojk]

Originally posted by deathman53
basically, NOT ALL THE TIME. A stroker makes more mid-top end, while a big bore makes more torque. Of course the cam, carb, air intake and pipe have an effect on this too. That really is a question for the person whom is selling you the bore/stroker kit. Keep in mind a stroker kit involved rebuilding the bottom end and buying a stroker crank or having yours modified. A big bore usually involves buy a bigger cylinder or having yours put a new sleave in.

This isn't true. A stroker will give you better low end because the piston has more leverage on the crank making it easier to spin the crank. The bigger bore creates more vacuum letting the cylinder ingest more fuel and air which in turn creates more power all around.

[pro-rider46]

Originally posted by gojk
This isn't true. A stroker will give you better low end because the piston has more leverage on the crank making it easier to spin the crank. The bigger bore creates more vacuum letting the cylinder ingest more fuel and air which in turn creates more power all around.

yeah i aggre, hotrods makes a preetty nice strocker, its a +3 which is calculated to a 470. and if you plan on boring you stock cylinder is cost more than most people think. you have to get it replated (cause the 450r cylinders are nikasil plated) or you can get a sleeve put in. which is also exspensive.

[250X_project]

As far as HP, a stroker will give you more ponies compared to the same cc increase that a bigger bore size would give you.

Also, the longer the stroke the slower the engine may rev. Yet with such a short stroke to begin with a 450 should do just fine. Also lightening the flywheel can counteract this effect is necessary.

Personally, I would go with both! :D

[250rmike]

also you amy want to pay attention to how big you can bore the cylinder and still be reliable without the sleeve cracking and some big bore cylinders will require having the cases machined to fit. if it were me i would send you motor out or find someone who has done atv motors specifically the 450 motor and have them split the cases and put a stroker crank in/ more reliable in my opinion but the decision is yours and yours alone to make. also try calling some engine builders and see what they recomend

[wilkin250r]

Wow, I'm really surprised. There is a LOT of misinformation and garbage floating around this thread.

There are LOTS of different factors to power delivery, so keep that in mind. Camshaft and porting are the biggest factors in power delivery, but let's assume all those things are equal.

As a general rule, a stroker will give you more low-end grunt. The longer stroke will increase torque, but it also doesn't rev out as well. This would usually benefit riders in tight terrain like woods, trails, and XC racing. It requires a complete bottom-end rebuild, which is often expensive.

A big-bore will often rev out better than a stroker of the same size. You still get an increase in torque and power, because of the larger displacement, but you end up with better top-end performance. The are almost always cheaper (I'm not sure why you found the opposite) because the only involve the top-end. Also, many garage mechanics and tinkerers have the ability to do a top end and install a big-bore, but don't have the ability to rebuild a bottom end. This can further reduce costs by doing the labor yourself.

Now, like I said, there are many factors involved. With the correct porting and camshaft, you can get a stroker to rev out really well, it's all part of the entire build. But this knowledge should give you some basic guidelines to making an educated decision.

[redexrider4290]

so the stroker will give me more low end and the bore will giver me more mid-top

which will be more reliable?

will the stroker rev slower than stock?

thanks for all the input i apreciate it

[250rmike]

a stroker will rev slower than stock because of the longer length the piston has to travel now will you notice it on a atv prolly not much.

[redexrider4290]

i didn't mentin this but i have a duncan fatboy4 full exhaust and a k&n w/ airbox lid removed and rejeted carb

will this effect how my engine performs with a stroker. or a bore?

so i am still unclear on how exactly my bike will perform with each?

If i get a stroker will my bike rev slower? because to me that sounds like i will go slower not faster?

thank you guys for the input i have been counting on this site for years now and i have yet to be mis-guided THANKS

[nicker71]

redexrider Im in the same boat as you. I was planning on replacing my stock crank on my yfz this winter. I saw that hotrods offers and new +3mm stroker crank and it was only $100 more than the WR I was going to put in. I race XC and the extra torque would be nice. There are a coulple people building their quads with the new +3mm on another site. Im waiting to see their dyno numbers and what they think about the setup. I could allways add a big bore to the crank for more power but I dont think all that will be needed.

The bigger question for me is will the stroker crank be more reliable than the big bore??

very nice 330R trailwart!!!

[250rmike]

a storker will and should be more reliable if built correctly. there is less ring cylinder contact which equals less heat. also depending on how big you are boring the cylinder if you go with just a bore job there may not be enough of the eall left to successfully disipate the heat another problem is if you bore it all the way out then you will be replacing the cylinder/sleeve next time you have to do a rebuild try searching for more info. im not sure how everything is on your guys bikes as i have never owned one or tore them down

[redexrider4290]

but will a stroker increase power? i mean if i put the stroker in i won't be geting anything less than stock right? wouldn't it just be improving?

[250rmike]

yes your power will increase