i was woundering about bore x stroke which is more important when buying a quad


these are the two models i was woundering about, which one would be better?

2008
honda recon 250 2x4 suzuki ozark 250 2x4
bore x stroke bore x stoke
68.5 x 62.2 mm 66 x 72 mm

 

It would depend what you're looking for. Torque or horsepower. Without going into too much detail, the common theory is that an engine with a larger stroke than bore (under square) will favor low end torque, and an engine with a larger bore than stroke (over square) will favor upper end horsepower. That is if everything else, but the the bore and stroke, were identical. Engine designers have ways to tune and tweak things so it is rarely a level playing field.

 

Id look at other factors, neither of those machines are powerfull enough, or have the potential where you should even think about the bore + stroke.

Not saying they are bad, they are great reliable machines that will probably do anything you want.

Ride em both, see which handles better, and rides better, thats the most important.

 

http://en.wikipedia.org/wiki/Stroke_ratio


The Honda is a little bit oversquare, and the Suzuki is a bit undersquare....but neither so much that it is going to make a huge difference. The ultrafast sport quads with very light engines (like the 450's) are all very oversquare. Utilities on the other hand, need low end torque so they tend to be undersquare. Maybe the Honda will be a little more sporty, and the Suzuki a little more utility like (????).

I have onwed the Honda, and it is as near perfect as a small 2wd utility can get!!! Do however, avoid the ES shifting option....

 

Hello,
before choosing anything, first you have to define what you want to do. Since these two engines do not look like being much different, many other factors come into play. Let me explain.

As Rkangel777 pointed, the longer stroke engine would favor torque and the other one HP. Since you did not provide other important details like con. rod length which brings me to "n" ratio (rod to stroke ratio), intake runners and cams, we only assume the engine builders of these 2 engines made choices in regard with bore and stroke....

With bigger bore, you can fit bigger valves so better airflow... its easier and faster to fill a wide and short cylinder than a tall narrow one so the short stroke should be better for high rev so a good guess is that this engine as more cam (longer valve opening periode and maybe, more lift) than the other one. It's intake runner(s) shoud be shorter and wider to promote high(er) RPM. Gear ratio of the transmission would be a bit shorter I guess.

On the other side, "stroker" engine promote torque by giving more leverage on the crank for the con. rod and tend to yeld more torque. We can guess that the cam of this engine gives more power in the mids. Intake runner should be a bit longer and narrower. Transmission gear ratio are guessed to be longer to accomodate the somewhat "torquier" engine.

Now on to "n" ratio. the rod to stroke ratio is a determining factor in engine durabitlity. In general, if all other parameters are the same, the lower the n ratio, the more "shaky" the engine is. Plus, the lower the n ratio is, the more stess the rod/piston assembly will make on the cylinder wall so cylinder will wear "faster".

Before I forget, you might be interested in generally accepted "maximum safe RPM" which is 4000 feet per minutes of piston travel (well... among car engine builders at least). Other factors come into play here like bobweight and components strenght but stick with 4000ft/min anyway on a stock non all-out racing engine and durability will not be affected, generally... [img]i/expressions/face-icon-small-smile.gif[/img] By knowing this, the stroker motor probably has a lower max RPM...

this is only "a grain of sand on a florida beach" in regard to how much complex engine building is and some other people on the forum will probably want to point out other facts but I think you get a good picture now.

Now with needs and driving style.
Can only talk for me so lets say both engine are not too peaky (power only in a narrow RPM band) and provide much enough power to get the job done, I would take the stroker because I like to get a good kit on tap from the start while other might want the engine that keeps pulling more and more and more while going higher in the rev (like -> difference between 400ex and 250r guys). But in the case both engines are "insuficient" at scarring me than I would take the higher revving engine and play with sprokets to get more acceleration.

Now, you will have to try both quads to see which you prefer not only based on engine alone but also regarding handling, jumping carateristics and the not to be forgotten "easy or not to fix" and reliability. You might also want to check aftermarket parts before buying if you plan modifying it...

Hope it helps

 

...probably more info than a guy picking an entry level 250 needs!

 

<div class="FTQUOTE"><begin quote>Originally posted by: reconranger

...probably more info than a guy picking an entry level 250 needs!</end quote></div>



ya think? just mebbe? yeah. me too. [img]i/expressions/face-icon-small-happy.gif[/img]

Just for perspective a BB is 4.5 mm diameter. 2.5 mm is less than 1/10 of an inch. I wouldn't think 1/10" difference in bore diameter would make much difference. If it was 50x80mm vs. 80x50mm it would make a difference but they're both close to square. And they're just 250s so if one has more torque or whatever it's not going to much difference is it?

 

<div class="FTQUOTE"><begin quote>Originally posted by: jumbofrank

<div class="FTQUOTE"><begin quote>Originally posted by: reconranger



...probably more info than a guy picking an entry level 250 needs!</end quote></div>







ya think? just mebbe? yeah. me too. [img][/img]



Just for perspective a BB is 4.5 mm diameter. 2.5 mm is less than 1/10 of an inch. I wouldn't think 1/10" difference in bore diameter would make much difference. If it was 50x80mm vs. 80x50mm it would make a difference but they're both close to square. And they're just 250s so if one has more torque or whatever it's not going to much difference is it?</end quote></div>

Like you say, wont make much difference with so minimal differences... Its not like comparing chevy 427ci with 5.0 L BMW V10.. only well experienced drivers will see actual difference I bet.

 

dont say 250cc is entry lvl, im only on 110cc [img]i/expressions/face-icon-small-tongue.gif[/img] (working on better tho)

 

That is QUITE the difference in stroke. The bore doesn't mean much, but stroke goes a long way. It gives more leverage on the crank. And there's nearly a half inch difference between the stroke on those two. Just like a 302 and 351w, a 302 is 4inx3in and a 351w is 4inx3.5in. Lots more torque down low.

Yes, other things come into play, but the 302 is a rev king and the 351w is a torque monster.