registered user

banshee hub appears to be the same essential design as every other 2t engine on the planet. ive never had a problem with them bolts going loose with 7ftlbs and no loctite on other engines. the problem with doing them hand tight is most people cant gauge torq very well by hand and thats how them bolts get stripped out.

increasing the stroke doesnt necesarrily meen you would raise the cylinder, like a stock stroke engine with 4mil crank for example. although i suppose you could use a spacer. but as the stroke increases, at some point, ideally you would want to increase the rod length. the longer rod would position the cylinder higher, assuming you were keeping deck heights and wristpin locations the same. ya alot of crankcase compression theories out there im sure. seems like back in the day the hot thing to do was try and force the mixture into the cylinder. now i think ideas have shifted towards letting the pipe do more of the work pulling it in there is nothing posted about honda vs yamaha or kart vs atv. it was stroke vs bore last i checked. i dont know how else to explain this besides a oversimplified pic. since there is no exact cc comparison between the cp cylinders, we will use the closest match possible, which still should help you make sense of it. if we compare the 68x68 cub (494cc) vs 72x58 dm (472cc), hypothetically we set the timing on both engines to 130* and width of 20% of bore diamter. you would end up with something like the pic. if you took the time to do the math in a real scenario you would see the black port (68x68 cub) is larger in area.

if there was a 10mil 64bore cylinder it would be interesting to see what happened if you put a 14mil crank in it with fairly long rod

what are you talking about. are you referencing the straight up and turn style of trans ports or something else ?

we not comparing honda vs yamaha. the manufacturer is irrelevant. we are comparing short stroke big bore to smaller bore longer stroke. how can the engine rev and make power if its running out of breath because the transfer area is smaller ? i only mentioned the 72stroke x 66 bore because thats pretty impressive to hit that kind of rpm. i believe its partly (maybe mostly) because its longer stroke in relation to the piston and no i never cc banshee trans volume. maybe someone else has. be interesting to see what it is

this may help explain better what i was saying. these are my beliefs. everyone is entitled to think otherwise. like i was saying about keeping the cylinder high. if you have a cylinder of say 250cc, how much mixture volume can you pack in there ? perhaps allitle less than 250cc, maybe even more than 250cc. i guess it depends on how well the engine was designed and its state of tune. now remember crankcase volume is usually many times larger than cylinder volume so only a partial amount of the case volume will make it to the cylinder each cycle. so if we have a real good running engine and can fill the cylinder with say 300cc volume then we want it as close as possible to the cylinder because it only has a very short time to make it there. if we try to get the 300cc of volume in the transfer tunell area, that would make for a short ride to the cylinder and a better chance that all of it will make it. 100cc transfer tunells doesnt do much good because then it will just try to pull any more mixture that it needs from other areas that are farther away, which takes more time and time isnt on your side. not to mention if this volume is located in the tunells it doesnt have to go through piston windows or around corners or other obstacles etc. so this is one reason why i like longer strokes and long rod. it lifts the cylinder and increases the trans volume. heres some photos of a old honda cylinder. its not right down to the nats ass but it will give us a close approximation what these tunells hold for volume. 500cc cylinder volume but the tunells only hold about 150cc x 2 which eqauls 300cc for all 4 tunells. i didnt factor in the boost port but i think that port is far less important and its steep upward angle doesnt flow nearly as much volume as the side transfers. so i have a 500cc engine with only 300cc of volume readily available in the tunells. maybe this engine wouldnt benefit from more trans volume, i really dont know. it is a large engine and its port design is far from ideal. but on a smaller better designed engine, if you only had 1/2 to 2/3 of your cylinder volume sitting in the tunells, i think you might be cutting yourself short. so flame on if you want but it makes sense to me. theres something else to point out about the longer stroke stuff. i like picking the brain of kart guys. one dude has a cr250 with upper mid 60hp (67hp was the dyno i seen) on race gas and its power peak around 11k rpm. this is 72 stroke engine. some of that rpm can be attributed to the pipe and probly the custom design ign curve, head design etc etc but i think alot of its rpm is because the undersqaure engine has more port surface area which has alot to do with where the engine runs out of breath and cant make any more power. not knocking anybody but some people say the short stroke stuff can rev, well all the short stroke stuff ive seen around here drops off before 11k, sometimes well before 11k.

calvin made these cylinders to make you guys happy and keep this sport going. if he were to make a engine from the ground up it would be different im quit sure of that

everyone says 100hp from stokestroek and bore cylinders. dyno section has 7mil dm at only 120hp ?? 220cc more only gets you 20hp ? lame. because huge piston short stroke aint worth a fuk. if you cant see it oh well. sorry of the rant but i dont understand some of you guys and if your thinking clearly

lets compare 78x58 to 71x70 both same 554cc . i know theres no such engine by why not. makes more sense than one thats redicously over sqaure

lets think about all this for a minute. you should be striving for the most port surface area you can. large piston with short stroke does not lend it self well to that, not as well as a long stroke. large piston generally is heavier and surely is more prone to deto because its dome is hotter from the increased surface area not being able to transfer heat as well to the walls and water jackets. combustion flame will have farther to travel with large piston diameter. other stuff nobody ever thinks about with the short stroke is how much lower on the cases does that put the cylinder. it matters because it can shorten your transfer tunnels and reduce their volume. neither are a good thing really.

this how i do it

might go look at a stock banshee next week. not real familar with atv's. is there a vin somewhere on the frame so i can be sure its the year he says it is ? is a number on the engine that supposed to match the frame vin ?

drill that sumbitch out. maybe some gold is in there

some times its a compromise between not grinding a area as large as you think it needs to be in order to preserve the structual intergity. whether the sleeve will crack and cause problems is hard to say as your the only one with a birds eye view

i hear ya on the tunells. it is what it is. something you may consider on these cylinders or future ones if you do another set, is keeping a fairly high upwards angle as they enter the cylinder. this will decrease the angle in the upper portion of the tunell where it turns and heads to the cylinder. trying to go into the cylinder flat with a straight up tunel design puts a sharp turn in your tunell. pointing the transfers up will lessen the angle of the turn. i forget the intended purpose of your engine ? or maybe you never mentioned it. anyways on the stuff i do i dont normally get concearned with the intake being to large. really you want to put in as much mixture mass as possible. if you increase mass transport 15% and lose 14% velocity your still gaining. some people over look the reed block as well. on some engines the reed block can be modified quit a bit to work better. on the engines ive dealt with the stock reed block windows seem to be too small and the petals are restricted in how high they lift. ive modified a couple different oem blocks and they work well. you may not be using oem reed blocks but i thought i would mention it anyways since alot of people think oem stuff is junk and throw it in the trash. alot of times it is junk but often times it can be modified to work pretty well

this is a neat little bugger with a exh valve. never rode one but i bet it goes like a raped ape. ktm 85cc

i think exh valves are a great idea but with so many design variations some will be more affective than others. if your powerband is from 7-9k rpm and the engine never operates outside that window like some drag racers for example, i dont see any reason to complicate things with a exh valve. for everyone else i think a valve can be a valuable addition. anybody thats tinkered with non exh valved engines will probly tell you its difficult if not impossible to get the engine to run exceptionally well across the board without a way to vary the size of its exh port.

straight up and turn is basically what it is and i cant think of a worse way to make a transfer tunel. however this is unavoidable when you have a inline twin or multiple inline cylinders so close together, but theres really not much other choice in that situation. rotating one of the cylinder forward 45* or 90* would get rid of any limitations on cylinder design but im not sure such a engine would be good in a off road chassis, which is what these machines were origianlly intended for in yamahas eyes. calvin has done a good job on his cylinders, considering the engine design he had to work with. i think he put alot of effort into making the most out of a less than ideal situation

im not a fan of a tall narrow window as it doesnt support good power. 70% width or there abouts seems to work well and doesnt require a huge arc on the roof or large corner radius. ya some people will probly brag how they made the window much wider but then you need large roof arc and big corner radius (which isnt good for power either) to keep the piston and rings from eating themself in short order, so youve really gained nothing by doing this. if you want or need to make the exh area bigger than approx 70%, cutting in aux ports should be the next logical step. then you can maintain a nice window shape on your main port that doesnt chew up the piston and youll gain the extra area needed via your auxillaries lowering the exh floor isnt something i do mostly because the exh gas needs to be gone or mostly gone before the transfers are uncovered , so what does enlarging the lower portion of the exh accomplish ? if your exh isnt long gone by the time the piston gets near the bottom of the stroke, youll have some serious problems with it trying to push back into the transfers and crankcase resulting in a poor running engine. lowering the window also creates more volume in the tuenll as well, which may weaken the pressure fluctuation. if you had a bicycle pump and tried airing up a tire, i dont think you would make much progress with a large hose as you would spent quit a bit of time pumping up the hose rather than the tire. i believe this to be a similar situation with a large exh tunell

window makes more of a difference than the tunell ? im not sure i could agree with that . without a well shaped tunell , the window meens almost nothing as far as im concearned. i believe this to be even more important with transfer ports. anybody thats been around 2t enngines over the decades has seen transfer ports and all the ports in general evolve over time. alot more science behind it than what people think i would dare guess most 250's back in the day would be lucky to see 35-40hp. all the modern ones are 45-50. theyre more power today because of a few reasons and superior tunell shapes is one of em

sweet. used cylinders are cheap enough you can get another set if you go past the point of no return but ive learned its best to make smaller more logical modifications rather than just grinding the fuck out of everything and hoping it works. plus youll learn more along the way

i think alot of stuff people do (my self included) looks good on paper but doesnt do much in actuality. like messaging off that floor lip. piston is only at bdc for a very brief moment, remainder of the stroke the piston is above the floor and creating a ledge of its own. doubtful it would matter if you messaged off the floor lip or not

ive seen a few that go in flat and turn down. i never cut the flat part back in. this drawing doesnt appear to go in flat either

structiions r fer dummi3s

do you guys think a better performing pipe is still down the road alittle ways ? maybe cpi,shear, led, sniper etc just havent figured it out yet. i have hard time believing the available pipes are good as its gonna get