fast500#12 Posted October 7, 2005 Report Share Posted October 7, 2005 i'm just currious why people say that boring you cylinders isn't going to do any thing for you. a larger combustion chamber more fuel = more power. the ounce or or so that the larger pistons (depending on the size you go to) add should be more than off set by the increase in power. a long rod stroker will add just about as much extra mass rotating as say a .020 bore. granted the stoker will build more torque than a bore due to a longer time the piston is pushed by the explosion of the fuel charge. have people forgotten the old saying no replacement for displacement. maybe it just me but i don't see how putting longer rods on your cranks and a spacer under you cylinder is doing any thing more than keeping your stroke the same length because you haven't moved the pin on the crank further away from center of rotation on the crank shaft and lifted your combustion chamber 4 milimeters higher.to truely make it a stoker you need to move the pins further away from the center line of the crank shaft its self thus giving you more distance traveled up and down. once again i don't know it all and i don't know if the stroker cranks are made that way, ( i've never had one to compare to a stock crank), i am not an engine builder i am just curious about how stuff works. feel free to set me straight. Quote Link to comment Share on other sites More sharing options...
RNBRAD Posted October 7, 2005 Report Share Posted October 7, 2005 i don't see how putting longer rods on your cranks and a spacer under you cylinder is doing any thing more than keeping your stroke the same length Sure you will gain power with an overbore. Dyno #'s have shown it's minimal unless you significanly increase your bore size and or stroke. As for cranks, you may be confusing long rod cranks and stroker cranks, I'm not sure, anyway here's the breakdown. A 4mm stroker with long rods is stock stroke (54)mm + 4mm then adding 115 mm rods. The stroker comes from the big end pin is placed 2mm further out, giving a total added stroke of 4mm, 2mm up and 2mm down. Standard rods are 110mm and long rods are 115mm (wrist pin located 5mm higher) and you have to use 795 series pistons to compensate for the added 5mm pin height. Long rods are used to increase leverage and reduce side load on pistons. You can have a 4mm stroker with standard rods (110mm) or long rods (115mm) you can use wiseco 513s or factory yamaha pistons with the standard rods. Spacer plate compensates for the added stroke or you can do dome or head mods (stock cylinders) to compensate as well. Quote Link to comment Share on other sites More sharing options...
hittintrees srh Posted October 7, 2005 Report Share Posted October 7, 2005 no replacement for displacement. Rock On! Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted October 7, 2005 Report Share Posted October 7, 2005 yea, i forgot all the fast drag bikes are stock cylinders bored 80 over... going big bore is not going to give you power that stroking will...if it did, people would not spend thousands of dollars to build stroker motors... Quote Link to comment Share on other sites More sharing options...
Cotton eyed Joe Posted October 7, 2005 Report Share Posted October 7, 2005 Because Horsepower is a derivitave of RPM and Torque. Horsepower is the rate at which torque can be applied. To get torque, the best way is to lengthen your "torque lever arm". Even ever so slight, it adds up due to the relationship between RPM and Torque. The piston does have further to travel, so the RPMs aren't going to be there as easy but the added torque BUILDS more horsepower at the same RPM. Basically Horsepower isn't a tangible thing, but more like the result of an equation. Making your piston bigger will result in a bigger explosion, and "more" power, but the leverage against the crank will be the same. No advantage over the crank except what you can produce in an explosion rather than just lengthening that lever. And it does increase displacement. B x pi x H = Displacement. H is your stroke. B is the bore and pi is 3.1415972. Quote Link to comment Share on other sites More sharing options...
endofitall9 Posted October 7, 2005 Report Share Posted October 7, 2005 Im not sure if anyone else seen this "i'm just currious why people say that boring you cylinders isn't going to do any thing for you. a larger combustion chamber more fuel = more power" Wrong a bigger combustion chamber equals less power. Why do you think people run 18cc domes and shave thier stock head that is to lower the combustion chamber therefore making more power . The smaller area the fuel has to explode the greater the explosion is going to be and vice versa, The bore really doesnt matter that much you might see a fraction of a gain on a dyno but nothing serious. Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted October 7, 2005 Report Share Posted October 7, 2005 Im not sure if anyone else seen this "i'm just currious why people say that boring you cylinders isn't going to do any thing for you. a larger combustion chamber more fuel = more power" Wrong a bigger combustion chamber equals less power. Why do you think people run 18cc domes and shave thier stock head that is to lower the combustion chamber therefore making more power . The smaller area the fuel has to explode the greater the explosion is going to be and vice versa, The bore really doesnt matter that much you might see a fraction of a gain on a dyno but nothing serious. 423913[/snapback] Not going to pretend I know anything but I don't think this is compleatly right, people changes the domes which increases the compression which changes teh point at which fuel combusts. If you go to too high of a compression I believe it can actualy slow you down. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted October 7, 2005 Report Share Posted October 7, 2005 Not going to pretend I know anything but I don't think this is compleatly right, people changes the domes which increases the compression which changes teh point at which fuel combusts. If you go to too high of a compression I believe it can actualy slow you down. 423986[/snapback] too high of compression will not let the motor rev as freely... Quote Link to comment Share on other sites More sharing options...
rocketboy Posted October 7, 2005 Report Share Posted October 7, 2005 Not going to pretend I know anything but I don't think this is compleatly right, people changes the domes which increases the compression which changes teh point at which fuel combusts. If you go to too high of a compression I believe it can actualy slow you down. 423986[/snapback] thats somewhat true ,very high compression can kill rpm , spark,peak power .the squish bands clearance, width, and angle are as important as the final cc of the dome Quote Link to comment Share on other sites More sharing options...
chris642 Posted October 7, 2005 Report Share Posted October 7, 2005 bore really doesnt matter that much you might see a fraction of a gain on a dyno but nothing serious. 423913[/snapback] i think you will see a bigger gain with a boost bottle im sure he meant that a higher compression within a reasonable ammount is better, which is true. i wouldnt want anything over 200 PSI on a banshee, im sure you can but that seems a little to high for me. luckily on a banshee, no matter how high you go, it will still be cake to kick it over. anyone want to try to kick over a 240PSI RM250?? that was a pain in the ass, now at 200 PSI, it still is a pain, but managable!! Quote Link to comment Share on other sites More sharing options...
fast87 Posted October 7, 2005 Report Share Posted October 7, 2005 i don't believe it has been mentioned yet but boring your cylinders strictly to get more power is hogwash, lets say you take your nice clean cylinders on a stock bore, and max them out at .100" over stock, 50 hours later you break a ring, it scratches up the right cylinder just a little, enough so it will not run reliably, and also enough that it NEEDS to be bored .010" over, there is no room...O SHIT what do you do now?? resleeve the cylinders or buy a new/used set of jugs...all for that extra 1.4712390HP you just gained from the pointless .100" overbore...buy a new set of spark plugs, clean your air filter and dial in the jetting, there's your extra 2-3HP right there...live and learn i guess, go ahead and max out your cylinders, just please don't make pointless threads about "resleeving your cylinders at home in 3 easy steps" because there is no such thing, always bore the minimum amount each time, just enough to make it round and all the scratches are gone(yes, crosshatch is a GOOD thing) ~Mark~ Quote Link to comment Share on other sites More sharing options...
endofitall9 Posted October 7, 2005 Report Share Posted October 7, 2005 pk so your saying that making the CC smaller doesnt raise compression and allow for stronger explosions? If that is is then why is it when you put smaller domes in your head the compression goes up. I've been studying this crap going to school for it no trying to be a hot shot just trying to state the fact. Also you have to run higher octane with a smaller dome because of the compression. Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted October 8, 2005 Report Share Posted October 8, 2005 (edited) pk so your saying that making the CC smaller doesnt raise compression and allow for stronger explosions? If that is is then why is it when you put smaller domes in your head the compression goes up. I've been studying this crap going to school for it no trying to be a hot shot just trying to state the fact. Also you have to run higher octane with a smaller dome because of the compression. 424009[/snapback] Point is you can bore the cylinders and change the head to compensate for any compression lost with the boring... It's not that it does not make the bike have more HP it's that it is WAY better to increase the HP of your bike in other ways... A new sleve and Porting job gets expensive to maintain....Better off going with aftermarket cylinders... It was all about displacement and weight of the bike then we would be seeing raptors wining drag racing... Edited October 8, 2005 by Justintoxicated Quote Link to comment Share on other sites More sharing options...
hamuel Posted October 8, 2005 Report Share Posted October 8, 2005 a larger combustion chamber = more fuel = more powe this statement is so true. a banshee with .70 overbore with 120 psi and a banshee with stock bore at 120 psi for one is something yah can't compare each other 2. for the simple fact yamaha has suck sucky castings of those jugs it's not funny!. but if the cases were exactly the same the .70bore bike would product a little more power not to much but a little Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted October 8, 2005 Report Share Posted October 8, 2005 i don't believe it has been mentioned yet but boring your cylinders strictly to get more power is hogwash, lets say you take your nice clean cylinders on a stock bore, and max them out at .100" over stock, 50 hours later you break a ring, it scratches up the right cylinder just a little, enough so it will not run reliably, and also enough that it NEEDS to be bored .010" over, there is no room...O SHIT what do you do now?? resleeve the cylinders or buy a new/used set of jugs...all for that extra 1.4712390HP you just gained from the pointless .100" overbore...buy a new set of spark plugs, clean your air filter and dial in the jetting, there's your extra 2-3HP right there...live and learn i guess, go ahead and max out your cylinders, just please don't make pointless threads about "resleeving your cylinders at home in 3 easy steps" because there is no such thing, always bore the minimum amount each time, just enough to make it round and all the scratches are gone(yes, crosshatch is a GOOD thing) ~Mark~ 424002[/snapback] word up! Quote Link to comment Share on other sites More sharing options...
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