first banshee...few questions

[fasterblaster09]

Just bought me a 2003 banshee, only has a mild port and polish, reeds, and pipes. I was wondering what coolant I put in it, and should I do 50/50 or what?

[IcutMetl]

I suggest Engine Ice; it's already mixed for ya and it'll help keep your temperatures lower.

[wingnut548]

I agree its the only thing I'll put in mine:D

[fasterblaster09]

thanks guys...man is this thing a blast! It's an 03, +4 swingarm, mild port and polish, boyseen reeds, and cpi out of frame drag pipes. I got it for $1500, I got the whole bike, another frame (a-arms and everything), two swingarms, cool head domes, one keihin carb, two used pistons, and a bunch of misc stuff, and the cpi's (they wernt on it, it came with the fmf fattys and toomey silencers. today we put some the cpi's on it and put an adjustable timing plate to make it run right, and man is it fun! I always had a four stroke. I only raced it against a piped 450r today, but it wasn't much of a race :devil: .I will be able to test it out more this weekend at the L.A. dunes. sorry for the long post, its just awesome lol. what are other things I can do to make it faster? I want to keep it semi-reliable and don't have to worry about breaking something

[IcutMetl]

You can save lots of money by keeping your jetting tuned right; I think poor jetting leads to a lot of situations that give banshee's bad names. Other than that...yea they are a blast- go have fun!!

[fasterblaster09]

how do I know if the jetting is off? it seems to be running great, and my brother law says the same, he races/works on them.

[Hondamaster5505]

Fast and reliable? A 421cc cheetah cub that's properly tuned. 4mm stroker crank, with 68mm cheetah cub cylinders.

[fasterblaster09]

And something a little less expensive as of now lol. I was thinking cool head, or I do have one keihin carb, I think 36mm, but I dont konw if it's any good.

anyone know how pro wedges would do at the dunes? I can't seem to find any sand tires right now, and brother in law said I could use his pro wedges, I know they hook up in the dirt, but will it get me up the dunes? thanks

[2001warriorman]

Originally posted by fasterblaster09
And something a little less expensive as of now lol. I was thinking cool head, or I do have one keihin carb, I think 36mm, but I dont konw if it's any good.

anyone know how pro wedges would do at the dunes? I can't seem to find any sand tires right now, and brother in law said I could use his pro wedges, I know they hook up in the dirt, but will it get me up the dunes? thanks

Im sure theyd be better then a dirt tire. Don't use a single carb. NEVER especially with out of frames. You already got most of the stuff to make it fast you can get bigger carbs 34mm pjs are pretty common and will give you a nice increase. You can Also go to a 4 mill. Then you just need the crank long rod pistons, and a cool head with stroker domes. If you wanna save a buck you could always get a direct vitos bolt on cyliinder and get those ported and itd be even faster :devil: Theres loads of options

[Hondamaster5505]

34's are way big for just a mildly ported banshee. If it was aggressively ported or drag ported, it would be a different story.

For just a mild port job, and other bolt-ons, I would go with 28's. Maybe even 30's. If you go too big, you can drastically reduce power because you over-feed the engine.

But single carbs, there's nothing TOO wrong with them, but I believe you can get better performance out of twins. I was never a fan of single carb set ups.

[2001warriorman]

Originally posted by Hondamaster5505
34's are way big for just a mildly ported banshee. If it was aggressively ported or drag ported, it would be a different story.

For just a mild port job, and other bolt-ons, I would go with 28's. Maybe even 30's. If you go too big, you can drastically reduce power because you over-feed the engine.

But single carbs, there's nothing TOO wrong with them, but I believe you can get better performance out of twins. I was never a fan of single carb set ups.

For the mods he has he could probably get away with 34s. He'd just have to choke them up so there not feeding her to much. A single carb would just ruin the purpose of OOF pipes. If he got 34s his bike would always grow into them with every mod he got. I was only gonna have filters, ported cages, cool head, hot rods crank, advanced timing, and ported cylinders and he told me I'd be fine with 34s if I jetted them right and everything.

[fasterblaster09]

noo I don't plan on running one carb, im just saying it came with one bigger carb in the bucket of extras parts he gave me. I sure wish I knew more so I could understand what yall are talking about :o

I ended up buying some dune sliders with not too much lip on them, and kept getting smoked due to spinning. While I was there I purchased some geckos from someone there and they were a little better but not much, there was a stock banshee with stock pipes with haulers that just kept leaving me, which was pretty depressing...do yall know of a chart or diagram of some sort that shows the internals of the motor more so I could understand what yall are saying? I know a crank is what's hooked to the piston, so a longer crank gives more piston travel. that's about it

[Hondamaster5505]

Alright.

So there's the bottom end where the crank is. Unlike a 4-stroke motor, the crank is completely separate from the transmission and oil in the transmission. So the crank is in the front of the cases, sealed off. Behind that, in the mid-back of the cases, lies the transmission, which is separate from where the crank is and has oil in it.

So back to the crank. It sits in the front of the cases. There's two bearings right next to each other in the center, in between the two separate sides of the crank. And one bearing on each side of the outsides of the crank.

Both sides of the crank are separate. (Obviously)

Attached to the crank is the rod. The piston sits on the rod, through the wrist pin. The cylinder's, on the intake side, have cut outs for the air/fuel to travel in. (Ports) Instead of having valves like a 4-stroke. On the front of the engine, is another hold for the exhaust. (Exhaust ports)

As the piston moves upward, a vacuum is created beneath the piston in the enclosed volume of the crankcase. Air flows through the reed valve and carburetor to fill the vacuum created in the crankcase. For the purposes of discussion, the intake phase is completed when the piston reaches the top of the stroke (in reality, mixture continues to flow into the crankcase even when the piston is on its way back down due to the inertia of the fuel mixture, especially at high RPM):

During the down stroke, the falling piston creates a positive pressure in the crankcase which causes the reed valve to close. The mixture in the crankcase is compressed until the piston uncovers the transfer port openings, at which point the mixture flows up into the cylinder.

Mixture transfer continues until the piston once again rises high enough to shut off the transfer ports (which is where we started this discussion). Let's fast-forward about 25 degrees of crank rotation to the point where the exhaust port is covered by the piston. The trapped mixture is now compressed by the upward moving piston (at the same time that a new charge is being drawn into the crankcase down below)

Somewhat before the piston reaches the top of the stroke (approximately 30 degrees of crank rotation before top-dead-center), the sparkplug ignites the mixture. This event is timed such that the burning mixture reaches peak pressure slightly after top dead center. The expanding mixture drives the piston downward until it begins to uncover the exhaust port. The majority of the pressure in the cylinder is released within a few degrees of crank rotation after the port begins to open

Residual exhaust gases are pushed out the exhaust port by the new mixture entering the cylinder from the transfer ports.

The expansion chamber (an improperly named device) utilizes sonic energy contained in the initial sharp pulse of exhaust gas exiting the cylinder to supercharge the cylinder with fresh mixture.

The sonic compression wave resulting from this abrupt release of cylinder pressure travels down the exhaust pipe until it reaches the beginning of the divergent cone, or diffuser, of the expansion chamber. From the perspective of the sound waves reaching this junction, the diffuser appears almost like an open-ended tube in that part of the energy of the pulse is reflected back up the pipe, except with an inverted sign (a rarefaction, or vacuum pulse is returned). The angle of the walls of the cone determine the magnitude of the returned negative pressure, and the length of the cone defines the duration of the returning waves

The negative pressure assists the mixture coming up through the transfer ports, and actually draws some of the mixture out into the exhaust header. Meanwhile, the original pressure pulse is still making its way down the expansion chamber, although a considerable portion of its energy was given up in creating the negative pressure waves. The convergent section of the chamber appears like a closed-end tube to the pressure pulse, and as such causes another series of waves to be reflected back up the pipe, except these waves are the same sign as the original (a compression, or pressure wave is returned). Notice that this cone has a sharper angle than the diffuser, so that a larger proportion of energy is extracted from the already weak pressure pulse

This pulse is timed to reach the exhaust port after the transfer ports close, but before the exhaust port closes. The returning compression wave pushes the mixture drawn into the header by the negative pressure wave back into the cylinder, thus supercharging (a bigger charge than normal) the engine. The straight section of pipe between the two cones exists to ensure that the positive waves reaches the exhaust port at the correct time

Since this device uses sonic energy to achieve supercharging, it is regulated by the speed of sound in the hot exhaust gas, the dimensions of the different sections of the exhaust system, and the port durations of the engine. Because of this, it is only effective for a very narrow RPM range. This explains why two-stroke motorcycles equipped with expansion chambers have such vicious powerbands (especially in the old days before variable exhaust port timing existed). With the design illustrated here (i.e. a single divergent stage and a single convergent stage), the powerband of the engine will be akin to a 'light switch' - once the expansion chamber goes into resonance, there will be a HUGE, almost instantaneous increase in power. The powerband can be softened somewhat by reducing the angles on the cones, but this is simply due to a lower degree of supercharging. In order to get the best of both worlds (a large power increase and a wide powerband), the cones should consist of several sections, with a different angle for each section. Proper design of even a simple expansion chamber is somewhat of a black art, even though formulae exist that will get you in the ballpark (there is quite a bit more to this than simply choosing the appropriate angles and lengths based on sonic velocity - everything about the pipe comes into play, including the headpipe diameter and length, and the tailpipe ('stinger') diameter and length). Design of a multi-stage expansion chamber becomes incredibly difficult - it basically comes down to the old 'cut and try' approach in the end. This of course is not even considering whether or not the exhaust and transfer port timings and outlet areas have been optimized for expansion chamber use.

[Hondamaster5505]

By adding a longer stroke crank, it yes in fact makes the piston travel up and down farther. But you can't just throw it in there.

You need a cool head, with special cut stroker domes, as the piston will travel further upwards. It would hit the stock head and stop dead, unless you had the stock head cut for a stroker.

Also, it throws the port timing off. So you need to either buy a spacer plate, which raises the cylinders so the port timing matches again, or get your cylinders ported for the 4mil. I am not a fan of the plates as the port timing is never quite 100%. If you get it ported for the 4mm crank, the timing will be perfect and have more power.

[fasterblaster09]

thanks for the writeup, I get the general idea. I understand the first 3/4's of it. What is the "mixture"?

[Hondamaster5505]

Originally posted by fasterblaster09
thanks for the writeup, I get the general idea. I understand the first 3/4's of it. What is the "mixture"?

gas/oil/air

[fasterblaster09]

ok thanks! I noticed I have a slowww leak out of one (I think one) of the carbs on the over flow line (I dont have the hoses on them at the moment. any suggestions?

[2001warriorman]

Originally posted by fasterblaster09
ok thanks! I noticed I have a slowww leak out of one (I think one) of the carbs on the over flow line (I dont have the hoses on them at the moment. any suggestions?

Mabey your floats are sticking some tap the side of ur carb with a screw drive or something. Dont bust it but give it a good firm tapping a couple times and see if that works. Always works for me atleast