03crawldaddy Posted April 25, 2012 Report Share Posted April 25, 2012 I have been around motors and building them for awhile. I have mainly built high performance 4 strokes and just your average rebore, rering 2 strokes, all sorts of car and truck motors and diesels. I got a banshee in pieces a little while back in a trade for some steering stuff and this will be my first high performance two stroke build. The main reason I am posting is I see a lot of you guys talk about psi as a guide for running high octane fuel. I was always taught that your compression ratio was your biggest indicator of the need for fuel, along with head design and squish. I would believe it could be different on two strokes because of your exhaust ports and other things just like cams on four strokes. But I was wondering if some of the more experienced guys could explain it more. I see alot of posts sayin "if your at 155psi you need race fuel". Please explain to me more, and please don't bash me too much cause I'm a new guy. I've been reading this site for a while and just signed up. Quote Link to comment Share on other sites More sharing options...
Phelps Posted April 25, 2012 Report Share Posted April 25, 2012 all sorts of factors determines octane needed to prevent pre detonation. compression, timing, pipes, etc. but for the most part anything over 150 usually need higher than 91 octane. stock motor with off the shelf domes, standard mid range pipes with no added timing will usually do fine on 91 even with 150lbs i have done it, but doesn't mean it will work for everyone. you mentioned high hp bike. i don't know what your idea of high hp is, but i would suggest talking to a builder about your end goal power wise and let them guide you to what you will need. some builders have certain setups down so well it is generic. x base gasket, x domes, x timing etc. short story is no one says compression ratio because in the car world the piston can determine the end psi. for the most part banshee pistons are all the same dome profile and compression ratio. hope this helps Quote Link to comment Share on other sites More sharing options...
fuller1986 Posted April 25, 2012 Report Share Posted April 25, 2012 call brandon at wildcard racing he will help you make the right decision, my mistake was not calling him early enough in my build but either way he got me straightened out and has a ton of knowledge on banshee motor's his number is on the forum sponsor page Quote Link to comment Share on other sites More sharing options...
03crawldaddy Posted April 26, 2012 Author Report Share Posted April 26, 2012 Thanks guys. I appreciate the info. I got a long way to go on this bike. The motor was trashed when I got it. The kid rebuilt and it was .100 over on stock cylinders. He had a lot of detonation. Rode it one time after the rebuild, busted a piston, slung the rod thru the whole top case and ripped the bottom up pretty good. He gave me a set of cases with it, but the lower has some chain whack. I was just gonna put it together all stock, but don't think I'll be very happy with that. So I'm having a hard time deciding what I wanna build. I wanna be able to out run all my buddy's 450's and the one kids 800 can am. I haven't bought much cause I'm not sure what I wanna do for my end result. We ride mostly wide up places not much tight technical woods. I need it to be pretty reliable too, not wanting to have to run race fuel. Is there anyone close to me? I'm in southwest Florida. The only place I've found is tony doukas racing, but no one really talks about him on here. He's only about 20 minutes from me. Quote Link to comment Share on other sites More sharing options...
maskmanLS6 Posted April 26, 2012 Report Share Posted April 26, 2012 Thanks guys. I appreciate the info. I got a long way to go on this bike. The motor was trashed when I got it. The kid rebuilt and it was .100 over on stock cylinders. He had a lot of detonation. Rode it one time after the rebuild, busted a piston, slung the rod thru the whole top case and ripped the bottom up pretty good. He gave me a set of cases with it, but the lower has some chain whack. I was just gonna put it together all stock, but don't think I'll be very happy with that. So I'm having a hard time deciding what I wanna build. I wanna be able to out run all my buddy's 450's and the one kids 800 can am. I haven't bought much cause I'm not sure what I wanna do for my end result. We ride mostly wide up places not much tight technical woods. I need it to be pretty reliable too, not wanting to have to run race fuel. Is there anyone close to me? I'm in southwest Florida. The only place I've found is tony doukas racing, but no one really talks about him on here. He's only about 20 minutes from me. you will need some port work and better intake , fuel delivery ,and exhaust to keep you running up front, especially if theres a big bore can am to compete with. research several options before you start spending money because there is tons of stuff out there for a banshee build. i just built a 60 hp trail machine and was amazed with the amount of after market parts and machining available for banshees. Ill be glad to give you any advice and knowledge i have to help out with your build. Im not a pro but after building mine i have some trial and error advice to pass on. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted April 26, 2012 Report Share Posted April 26, 2012 I have been around motors and building them for awhile. I have mainly built high performance 4 strokes and just your average rebore, rering 2 strokes, all sorts of car and truck motors and diesels. I got a banshee in pieces a little while back in a trade for some steering stuff and this will be my first high performance two stroke build. The main reason I am posting is I see a lot of you guys talk about psi as a guide for running high octane fuel. I was always taught that your compression ratio was your biggest indicator of the need for fuel, along with head design and squish. I would believe it could be different on two strokes because of your exhaust ports and other things just like cams on four strokes. But I was wondering if some of the more experienced guys could explain it more. I see alot of posts sayin "if your at 155psi you need race fuel". Please explain to me more, and please don't bash me too much cause I'm a new guy. I've been reading this site for a while and just signed up. You are very correct in that cranking compression does not determine octane requirements. Port layout, squish and dome design are some of the things that determine octane needs. The head on my bike is setup specifically for 91 octane at ~130psi compression. If i were to get into the 140psi range (say by running a thinner base gasket) i would be looking at needing higher octane fuel because the head was cut specifically for my combination and porting. Quote Link to comment Share on other sites More sharing options...
03crawldaddy Posted April 26, 2012 Author Report Share Posted April 26, 2012 Thanks couplex, that's what I was thinking also. And ls6, can you give me some info on your setup? I was thinking of a 60-70 hp build. I'm almost positive I'm gonna do a 4 mm crank, I had a friend of mine who had a new stock stroke crank send me one, but maybe I'll just save it for another build. I'm having a hard time deciding on a stock cylinder 4 mill port (not sure what kinda porting to get for my riding, thinking a dune?) a serval, or (don't slam me, an Athena 4 mill kit). The thing I like about the Athena is it comes with pretty much everything I'm gonna need minus crank from one place. I'm not gonna buy one off eBay. My buddy in Tennessee who messes with these bikes recommended wicked performance. I talked to them and they clean up all the ports and some other things for the same price. It comes with a better head with domes they can cut, wisecos, and all that stuff.. The guy I talked to seemed pretty straight up. If I go another route I'm pretty much starting from scratch. Any way I go after I make up my mind about that, I'm gonna use my stock carbs for now, advance the timing, can't decide on reeds, probably v force since that's what we always ran in our dirtbikes, k&n pods, dmc alien pipes for now, see how they run cause I've never seen them on a banshee before, I don't like them I was thinking of some cpi's. What do you guys think about that? I know y'all are gonna have a big no for the Athena, but I've honestly heard 50/50 mixed feelings about it. Monty Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted April 26, 2012 Report Share Posted April 26, 2012 I've heard of Tony Doukas. I heard he makes jet skis fly and builds custom parts for certain things. But that was a while ago. Go 4 mil ported stockers. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted April 26, 2012 Report Share Posted April 26, 2012 If you check out the FAST website or call Jeff he can tell you that he has a few different setups that come as complete kits. Some come with crank and some don't....but it's not hard for him to turn around and pick up a crank on his shelf for it haha. Also there are different things to think about like fuels.....you said you wanted to stay on pump.....which is gonna limit you as of the power/build. The serval cylinders supposedly have incredible low end along with hard running top end power and have been able to make 80hp while still on pump fuels. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted April 26, 2012 Report Share Posted April 26, 2012 I'll get flamed for it, butt fuck it . Seeing you're close to TDR, go talk to them. Been on their web site and they have a lot for banshees. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted April 26, 2012 Report Share Posted April 26, 2012 Couplex, I'm glad to see you post what you did. I've been trying forever to get the 15yr old punks of this site, to try and understand that what their compression gauge says they have for cranking psi, means zero in determining octane needed for the particular engine. Compression ratio, efficiency of the pipes, timing, squish clearance and head design, are some of the more important factors to use. Perfect example, my Husky 346xp chainsaw has 185 cranking psi and runs fine with 91 octane. Remember they have jackshit for a tuned exhaust, so there is no "supercharging" effect of the cylinder, conservative timing, small carb bore, low exhaust port, lower compression ratio, etc, so low octane is fine. Now my banshee has a 14.8:1 comp ratio and only pulls 150ish on a gauge, from higher exhaust port, but pump gas won't work for my moto. Never go off of a comp gauge ro determine the octane you need!! This is the reason for probably 60% of the blow ups posted on here. Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted April 26, 2012 Report Share Posted April 26, 2012 If you wanted to ride trails with 450's, can am 800, run pump gas & still be able to lead the pack at will. I would do a 4mil 421 serval. As stated above they suppose to make 80HP out the box on pump gas with the right set-up. JMHO 1 Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted April 26, 2012 Report Share Posted April 26, 2012 (edited) Just wondering if this link will help a few people out with how to find out what there compression ratio is: http://www.csgnetwork.com/compcalc.html here is a video on how to calculate two stroke engine compression ratio: Edited April 26, 2012 by 252wheelieking Quote Link to comment Share on other sites More sharing options...
03crawldaddy Posted April 27, 2012 Author Report Share Posted April 27, 2012 Thanks everyone. Pretty good video. The can am and the 450r are dead nuts from start to finish. I figured the 450 would leave the hole a lil slower and the then come back on top end but not the case. They switch bikes and everything, same results. I guess I'll build it, see how it runs and go from there. Debating on the serval still, how is top end on them? Should I just go ahead and put bigger carbs on too? I gotta get to work on this thing, I'm getting tired of riding my all original 85 350x my dad bought new and the 06 Vinson 500. The Vinson is down with peeled nikasil and is waiting on a sleeve and piston. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted April 27, 2012 Report Share Posted April 27, 2012 a ported stock stroke or 4mil stock cylinder will take care of them. my stock stroke has no problem out running them. spending some time setting everything up to work together works wonders. knowing what your setup wants is key. no 2 are the same. little things like crisp jetting, gearing and knowing when to re-gear if changing riding surfaces and even tires make a bike that is fun to ride. Quote Link to comment Share on other sites More sharing options...
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