cool head dillemma

[PA_Banshee]

My friend has a dillemma with his banshee and asked me to try to figure it out for him. His 2000 Banshee has vito's power piston's, reed spacers, a 4 degree timing change, 320 mains, and FMF Fatty Pipes with PowerCore 2 mufflers. We just installed a Pro Design Cool Head on friday with 18cc domes. He was told that it would be fine to still use 93 octane with it.

First off the compression change dramatically changed his power curve. It used to be all top end with no mercy, but now it's more mid-range power. He's not all that upset with the power change due to the great cooling it provides but we think it needs higher octane fuel due to all the mods. There is a lil pinging coming from it now that was much quieter before.

The main problem is do we just try to put 115 octane race fuel in it or try an octane booster additive instead so we don't overdo it???

Has anyone here used the Cool Head with smaller domes? If so what were your results? After riding my banshee and his around for a few hours we could feel an obvious difference between the cooling of his and mine. Mine has a stock head that has only been polished and you could barely touch it because it was that hot. His was lukewarm and you could leave your hand on it all day.

[Banshee]

I'm not exactly sure what octane you use but when you use a smaller dome you should be using higher octane. I don't think an 18cc Dome whould need 115 but mayber 105. I would post this question to Scott of Soreracing there is a section in our preferred vendor section. He would probably have an answer for you.


Thanks

[PA_Banshee]

Thanks, we use 93 octane right now but the only other gas we can get is that 115. I'll send scott a message, but if I don't hear anything before the weekend we'll try an octane booster that claims somewhere over 100.

Thanks again for all the great help, I appreaciate it.

[Banshee]

Yeah I think some where in the 100 octane is best. I would think you would want a 16cc dome to run 115. Do you have someone around that sells VP fuels they have all kinds of Octane and you can order it by the drum. I think to run pump fuel you would be running a 20 cc dome.

[Hillclimber361]

My bike knocks on 93 octane gas because of the head being milled down. I usually use i believe it's VP additive octane booster, it's red stuff, it says it should raise the level by up to 20 points if you want. But you can use a little bit to only raise the level a little bit. It has mixing directions on it, it's real simple and works.

[TZ375]

We run TZ750s and RZ350s here and in Australia and there are some issues that remain the same.

First off, porting and pipes change the EFFECTIVE compression ratio at different points in your power curve.

Second, you have to get the squish clearnace right before you do almost anything else. if say your base gasket is too thick or the barrels are taller than spec ( or at the upper limit) then your squish band may be too wide. A tall squish band tends to increase the probability of detonation, so it pays to get it right. there are posts all over the internet on what "right' is, so speak to your favorite tuner.

Increased compression improves the bottom and mid range but tends to hurt the top end because of increased pumping losses. The trick is to find a compression ratio that works best for your type of riding. You may want to try a couple of different inserts to get to what works best for you.

Also keep in mind that different head shapes work at different parts of the RPM curve. Narrow squish works at the top end and broad ones for lower down, so feel free to experiment with different domes and see what works for you. Ignore all the hype and what other people do. We all ride differently and what works best for your riding style is the way to go - not what someone else uses.

Race bikes aren't quite the same as quads. We run long straightaways so we can't take as much compression as you guys, so we lose out a little of that mid range. We also can't use as much ignition advance at the top end, so we use ignition boxes that run more advance down low and less as the revs go up. Dyna do a programable CDI box for Banshees. WOLF probably do one as well. Now we're talking bigger dollars, so get the basic set up right first.

On TZ's historicaly stock bikes set up very carefully run faster and longer than all the trick ported high comp, super doodad machines. Make usre that what you have is working perfectly with the right jetting and compression and iginition advance. jetting two or three sizes off costs more HP than most accesories. Timing is the same. get it right.

A worn chain will cost you 1 to 4 hp at the rear wheels and may wear out sprockets or leave you stranded.

VP and Sunoco both do a range of fuels. We use VP C12 for most motors if we can get it. We also do a mix of Sunoco 100 unleaded and their 115 Octane, but my preference is to not mix anything other than oil and fuel and for that I use an Accu-Mix jug, available at www.accu-products.com

Avoid octane boosters like the plague. they are hard to mix accurately, add nothing in the way of power and really are just an expensive form of paint stripper.

Checkout any of the replacement dome guys for estimated compression pressure and the fuel you'll need, but try C12. If you are feeling rich, get a drum of the latest VP race gas MR8 or ultimate and feel the extra half a horsepower.

Check fuel:air ratio by readig the plugs or better still pull the heads and check. Unleaded leaves carbon and is impossible to read unless you are an expert. It also needs hotter plugs to burn off the soft carbon film.

So with race gas you should see a light gray or brown (depends on oil) and be prepared to go harder (colder) on plugs - say B9EVX in platinum or b10 if the plug shows signs of overheating. You can also use B9EGV or B10, but try to stay away from regular plugs with 1.3mm electrodes.

Life is a learning experience - feel free to experiment - you never know what you will learn - and keep reading too.

[Hillclimber361]

First off, what the hell is a Tz that you are bragging so much about, and are you a professional mechanic or something??? Also, i wouldn't diss on additive octane boosters, the knock stops, and it runs right, seems like it does the job, does it not?

[370banshee]

hey hillclimber every person is entitled to their own opinion. i think a tz750 is a 750 triple 2 stroke motorcycle. am i right TZ. and every banshee guy knows what a rz350 is thats the 2 wheeled street version of everybodies favorite quad the BANSHEE.

[TZ375]

Sorry that a different perspective upsets you.

I mentioned the TZ to let you know that I don't run quads, but that I was offering some advice that applies to all racing two strokes. The TZ is the water cooled production race motorcycle. I wasn't bragging about them - I was just letting you know that they are different in some ways.

As for what the heck is a TZ? Well, the first TZ came out in 1972 and was similar to the RD350 road bike of the time. Over the years Yamaha have produced them in 125, 250,350 and 750 versions. The 750 was a 4 cylinder with 66.4mm bore, 54mm stroke, 34mm Mikunis on reed blocks and made about 140hp. The current TZ250 weighs about 250 pounds and makes almost 100hp at the rear wheel.

The RZ, as your more tolerant and open minded buddy, 370 Banshee, mentioned is the motorcycle version of the Banshee with the same motor but with powervalves as stock.

What else would you like to know?

In answer to the other question I don't work as a mechanic, but I am an engineer and I have been crew chief and mechanic for a couple of motorcycle road racers with Aprilia AF1, RSR125, RS250, Honda RS125, RS250 and Yamaha RD350,RD400, RZ350, TZ125, TZ250 & TZ350. Hope that helps. I try to be open minded and to keep up with two stroke technology in all areas. Banshee parts often work on our RZ's for example.

If you want to use an octane booster go right ahead, but please share with us the scientific results of your tests. The reports I have read all say the same thing - no improvement in performance.

Sure if you are stuck in some small town and can't get good gas, then go ahead and mix some in as a get you home trick, but it is not the smartest way to protect your motor. The closer you take a motor to the edge of detonation, the more imortant it is to be consistent with fuel. Street gas varies considerably and summer blends are particularly bad.

If you run a high compression output, high compression motor, do not wreck it on cheap gas and octane booster. test it with different gas and see what it needs and if it needs race gas, then spend the money and schlep the gas drum around - it's cheaper than meltdown.

But, hey, it's your motor, you do what you want to do.

[Hillclimber361]

Im just wondering, if you say that octane booster does not work, i should say, no improvement in power. How much power does say race fuel add. At hillclimbs, a lot of guys try to run race gas on high compression engines, and we spank them on reg. 93 octane and booster to stop the knock. Sorry about not knowing what the 750 was, actually a friend of mine is building a drag quad with a Kaw. 750 H2 motor on it, but i never heard of the Tz or Rz for the matter, but i never got in to quads at all.