Banshee engine in streetbike-build suggestions

[ALewis182]

hello all,

I'm in the planning stages of a project involving a banshee engine and an older ex250 ninja rolling chassis and I need advice on the engine buildup. after cruising through ads and asking some friends I decided I should just ask some banshee riders what they like and who they reccomend and go from there

 

so the project is a fairly straightforward engine swap and I'm not new to this subject so I'm not gonna ask "how hard is it" questions or anything like that. what I need is advice on engine build. my thoughts are something like this: big bore, port work, aluminum head, and custom pipes. ideally straight 93 octane, but I'm not afraid to spike it with octane booster if need be. this is an around-town cruiser not a long haul bike. the bottom line here is that it has to be reliable. totally reliable.

 

I once rode a banshee with a GT-thunder prepped 73hp engine. it was otherwise unmodified and impossible to keep hooked up, and was rather pipey. hit hard, revved out, bogged on gearshifts. not a fun quad to ride for more than 30 seconds or so. what I want is a similar amount of total power but without such a rediculous hit. mid-and-up with just enough off the bottom to get rolling.

 

so who is known for reliable hi-output big bores? please leave names and numbers and I'll start making phone calls, and any of your reccomendations are greatly appreciated.

 

thanks a bunch

Adam Lewis

[1000dollabill]

in my experience with both street bikes and quads (owned a sv650s and currently own a gsxr1000 and banshee). I believe a built banshee motor would be way overpowering that chassis. but if you're gonna do it, i'd say 2into1 carb and a 2into1 pipe to get that sucker rolling. better make sure you get that motor balanced in that chassis. Also i'd invest in a nice steering dampner cause tank slappers are gonna be it's best friend when that suckers on and off the pipe with that rake.

[ALewis182]

my experience with streetbikes is limited to my 1987 ex500-not a great handling or powerful bike, and the testrides on a few 600's that came through the shop. I'm better with dirtbikes.

 

I'm left sorta scratching my head with the part about tank slappers-I dont want to build an inherently flawed bike and end up dead because of it. I guess I'll go dig out my "design of motorcycle chassis" books and see what they have to say. why do you think it'll do that? excessive weight transfer on/off the pipe?

 

I had assumed that good handling bike+power-weight=better bike but I've been wrong before...

 

also what are the effects of 2-into-1 parts on the twin cylinder? the sound of the single exhaust is...different and I dont particularly care for it, but I may do it if its beneficial.

 

thanks for your help,

Adam Lewis

[1000dollabill]

yup you are right on with the weight transfer. that combined with the rake on a modern sportbike and you could be asking for trouble. the 2-1 parts will give you more bottom end power, where the banshe usually lacks. but in the dirt a little roost will fix that.

 

if i were gonna do a similar project i'd do it with a "standard" motorcycle, not a rocket. those ninjas are pure junk anyway, atleast until you hit the six hundred class.

 

another thing to think about is where the center of gravityfor the powertrain relates to the sprocket position on your chassis. it's a different story with the opposite hybrid (streetbike engine in a quad.)

 

I'd be real cautious with your build, cause when something goes snap, crackle, pop, pavement at 70mph feels like pavement.

[banshee332]

if you do it see if you can find a rz tranny. It will drop right into a set of banshee cases, that way you will have a higher gear ratio.

[ALewis182]

alright, I read up on things a bit. all the following comes from "motorcycle design and technology" by Gaetano Cocco (an engineer at Aprilia) copyright 2004

 

"phenomena that generate wobble: Front wheel shimmy is usually generated by external stressors such as, for example, a small pothole or any other type of uneveness in the road surface which "pushes" against the tire, including lateral pressures. Wheel imbalance and eccentricities due to tire or rim deformation, repeated, obviously with the same frequency that the wheel rotates, can also provoke dynamic imbalance that generates wobble"

 

"Main Parameters that influence wobble: "

 

"Trail:Motorcycles with high rake angle and trail will certainly be stable up to high speeds, but when headshake phnomenon occurs it will be decidedly violent and thus difficult to control"

 

"Front end inertia around the steering axis...front tire...lateral flexibility of the fork..."

 

"A steering damper is very effective for damping wobble movements..."

 

so swapping engines dosnt really change any of those. in a straight line, the bike should essentially act like it did with its previous engine. I guess I'm still not seeing how the swap will increase the liklihood of headshake.

 

how do the high power sportbikes deal with this sort of thing? just steering dampers? the power curve of a two stroke is similar to that of a turbocharged engine, so how do the turbo 'busa guys deal with it?

 

I guess I'll just keep reading.

thanks,

Adam Lewis