rpxtreme03, on 16 February 2012 - 06:35 PM, said:

So I hook my 5 horsepower briggs and stratton motor to a thousand pound flywheel does the motor have negative horsepower? Does is become a -5 horspower motor? Can you show me how this is calculated?

I think everyone realizes that this is not the case. Yet, we are all amazed that you are willing to argue that a flywheel weight reduces horsepower. I don't understand why someone would rather destroy their credibility than admit that they are wrong.

Edited by mkeeping, 17 February 2012 - 06:53 AM.

cwf340, on 15 February 2012 - 01:19 PM, said:

I just traded my 2005 RM 250; which had a z start and 10oz FWW.  However, one mod I liked that was fairly inexpensive was adding carbon fiber reeds and a moose racing torque spacer.  The thing had traction for days.  It ended up being hard to spin the rear wheel in sand.  I recently purchased a 2009 300XC and added the rekluse core exp.  I prefer the core over the z start due to clutch feel.  I actually ride it like it doesn't have an auto clutch.  The rekluse is there for times I make mistakes from fatigue.

One thing of note, I added the FWW, Rekluse and then the torque spacer/cf reeds in that order with multiple rides in between.  I suggest trying them out for yourself and seeing what you like.  Rekluse offers a 30 day money back guarantee.  I had planned to pull the fww and see how it worked, but ended up getting a good deal on the 300.

Edited by expl_eng, 17 February 2012 - 07:09 AM.

2-Strokes 4-ever, on 17 February 2012 - 02:09 AM, said:

the increased traction off the bottom of the rpm range is one big benefit i find to the auto clutch. You don't have to perfectly let the clutch out even after an hour+ into a ride/race. The auto-clutch smoothly engages the clutch for you. If you want' a hard hit, you can still have the clutch pulled in, rev the motor, and dump the clutch faster.

MELK-MAN, on 17 February 2012 - 07:15 AM, said:

I think the stigma that Rekluse autoclutches are unreliable comes from the first models.  The install on the first models was far more involved, but every model since the Pro version has been solid.  If you can change out clutch plates, you can install the Rekluse Pro with no issues.  The Rekluse feathers the clutch perfectly coming out of corners, so unless your more than a gear to high, you going to come out of the corner quickly with no issues.

mjbd, on 17 February 2012 - 07:57 AM, said:

what's interesting i find, is that most riders that started out on the z-start pro, prefers it to the exp2.0 or core. They jsut get used to the feather pull lever i guess?? My A-Open buddy that i rode with yesterday has a 2012crf450r.. he has never had an autoclutch, he rode my bike 1 time with a exp2.0 but was still talked into the z-start pro by his tuner. He likes it, and after 1 race and a couple rides is finding fewer stalls very nice.. I simply couldn't stand the featherlite lever feel, and ride mine like it doesn't have an autoclutch, and just let it do it's thing at lower rpm without thinking about it.

mkeeping, on 17 February 2012 - 06:50 AM, said:

those are exact quotes from and article where its calculated using a dyno

Dwight_Rudder, on 16 February 2012 - 11:51 PM, said:

dwight seeings how you are the only one accually asking rather than jumping on it and saying its wrong i will answer you.
but YOU WRONG! its physics. when you add a FWW your bike has to turn that extra weight decreasing the torque you put to the wheels.

you guys are not seeing what they are saying because you are so completely brainwashed by the companys selling these things. they manipulate the dyno to show that the FWW is not decreasing power, a dyno is easy to fool in this case.

now im getting really sick of waisting my time trying to explain this to you guys. none of you are actually proving anything just repeating what the FWW companys are telling you. your only argument is "nuh-uh that can't be true"...gimme a break guys

what they are saying is that a motor will show the same hp and torque with a heavy FWW once the motor is up to speed and running at a constant rpm. tthe reason for this is because the FWW is a mass. a heavier mass takes more time and energy to move it. things in motion stay in motion with out the interference of friction or other forces. once the mass(FWW) is up to speed it can maintain that speed with little to no effort. this why it shows the same hp and torque as a light FWW when the motor is run at a constant rpm.
now as i said befor. when you are under acceleration and the FWW is trying to speed up it takes more enerygy to get up to speed than a lighter one. in this case your torque is energy. the heavier fww is absorbing your torque. the dyno sheet they are showing is rpm to rpm not distance down the strip.
its just shows them as they are acceleration. the x axis is your rpms and the y axis is your hp. they are showing the motor as it accelerates wwhere the fws are still resisting the motor because they are trying to be put into more motion. once they are moving though and they are no longer trying to spped up they will show the same hp.

now read that article again and see if it makes sense to you. if not im sorry but im not waisting any more time here

Edited by rpxtreme03, 17 February 2012 - 09:10 AM.

i dont' think you understand the very article you posted.. and the fact you have yet to indicate ANY further qualifications on your professional background does cast a little doubt on your credibility. It's awesome you race "b" class, but it does prove you have not raced enough to point out into the A class, thus have less experience than the A riders that have posted in this thread even if you are faster (not saying you claimed to be, just sayin). In other words, the A riders that are posting likely have ridden MANY more bikes with various customisation under offroad racing conditions.  Also, making your case with a single article about a car on a drag strip, where traction is much more available than a skinny single tire in the dirt.. has little relevance to THIS thread.

The reason the car with the heavier fww looses the race and is showing less torque AFTER clutch engagement, is because the motor REVS SLOWER. Not because there is a loss of horsepower. In fact, there is no loss of torque! The torque value is simply "delayed" for lack of a better word, but once the rpm reaches the same level as the lighter flywheel run (red lin on your chart) hp/torque would be the same. nowhere in the article your hanging your hat on, does it say you loose HP due to the heavier fww. It simply states that under drag race conditions (where you have optimal traction with sticky tires and paved strip with rubber laid down) you the heavier flywheel car gets a jump due to the additional stored energy in the heavy flywheel, but then never regains as much acceleration as it takes longer to rev after the clutch is fully engaged. Did you see the article i posted from the Motox action mag that i posted ? "do hfww cause a loss of hp - NO".. That was just one article i quickly found doing a google search, there were many other articles stating the same thing but i found it interesting it was from a fourstroke 250 site.  did you know that gearing does not affect HP on a dyno?

Edited by MELK-MAN, 17 February 2012 - 10:11 AM.

and if i post this enough times.. im betting world 4stroke champ Doug Dubach knows a little more than even you do. .
--------------------------------------
QUESTION TWO: HOW ARE YO-YOS LIKE MOTORCYCLES?

There are many similarities between a yo-yo and a motorcycle. The weight and size of the engine's flywheel determine how easy a motorcycle is to ride. And, flywheel weight plays a role in acceleration, throttle control, suspension action, braking and cornering.
QUESTION THREE: WHAT'S A FLYWHEEL?

A flywheel is a heavy plate of steel hidden behind the ignition cover. Its purpose is to smooth out the irregular motion of the moving parts inside the engine. It acts as both a counterbalancer and a power constraint on the engine. In doing these tasks, it creates a gyroscopic reverberation that changes the way the bike handles.
QUESTION FOUR: HOW MUCH SHOULD A FLYWHEEL WEIGH?

Before a factory's engineers can choose the proper flywheel, they have to consider seven factors:

• Overall engine weight: Lighter is always better.
  
• AC current: The size of the flywheel must be large enough to house the magnets that are used to produce engine spark. But, at the same time, small enough to make room for the stator windings without creating a bulky engine case.
  
• Engine acceleration: An engine builds speed quicker with a light flywheel and slower with a heavy flywheel.
  
• Inertia: A heavier flywheel carries speed further, but is also harder to slow down than a light one.
  
• Flywheel effect: Every rotating component in the engine and chassis creates its own spinning force (clutch basket, gears, chain, wheels, and how the crank counterbalances piston weight and stroke). The manufacturer needs to pick a flywheel weight that best accommodates all the independent gyroscopic forces inside the motorcycle.
  
• Angular momentum: Believe it or not, too much flywheel weight will make a bike hard to move around or corner.
  
• Intended use: The power characteristics and riding styles used on a 60, 80, 125, 250, 300, 500 and 4stroke all require different flywheel mass.

QUESTION FIVE: DOES MY BIKE HAVE THE BEST FLYWHEEL?

Most likely, but not always. Manufacturers do make mistakes. How? Some try to make their fourstrokes snappier, quicker revving and more two-stroke like by putting on the lightest flywheel possible. This can often lead to horrendous stalling problems and explosive acceleration (especially when the riding surface is loose or slick).
QUESTION SIX: DOES A HEAVY FLYWHEEL SLOW AN ENGINE DOWN?

Yes. Weight harnesses the rate at which the engine accelerates.
QUESTION SEVEN: DOES A HEAVY FLYWHEEL COST HORSEPOWER?

No. Heavy flywheels do not cost horsepower. They only change the way the power is transferred to the ground.
QUESTION EIGHT: CAN A HEAVY FLYWHEEL MAKE A BIKE FASTER?

Yes. But only if the engine characteristics are too snappy, powerful or explosive for the rider's style or track's terrain. A bike with an engine that's too explosive will accelerate quicker with a heavier flywheel weight.
Why? Because the weight smoothes and broadens the transfer of power to the ground. The power is delivered more consistently and in more of a conservative manner. The bike is more hooked up off the line and less volatile on the course. QUESTION NINE: CAN A HEAVIER FLYWHEEL CHANGE A BIKE'S HANDLING?
You bet. Toning down the abruptness of the power delivery makes the chassis less susceptible to sudden bursts of acceleration, excess wheelspin and engine stalling. Adding flywheel weight will make a bike feel less twitchy. If the tires stay hooked up, with less bounce or spin, the bike is easier to control.
QUESTION TEN: CAN A FLYWHEEL WEIGHT KEEP MY ENGINE FROM STALLING?

Yes. Since an engine takes longer to come up to speed with a heavier flywheel weight, it also takes longer to slow it down. The stored energy of the added weight keeps the engine turning under hard braking.
QUESTION 11: DO HEAVY FLYWHEELS MAKE A BIKE HARDER TO STOP?

No. Since the engine winds down slower, the transition from full throttle to full stop is much smoother. Additionally, the rider can use the brakes on a bike with more force, since the fear of stalling the engine is reduced.
QUESTION 12: DOES IT HELP STARTS?

Yes and no. Heavier flywheel weights can make a big difference on a concrete starting pad (or hard slippery dirt). But, on short, fast, dirt starting lines (like in Supercross) a lighter flywheel helps the bike jump out of the gate quicker, which allows the rider to get his bars in front of the rider next to him.
The difference between these two concepts can be seen at professional races. Four-strokes holeshot AMA Nationals (with their longer starts and concrete pads), while two-strokes holeshot Supercrosses (with their shorter starts and dirt pads).
QUESTION 13: CAN A FLYWHEEL WEIGHT IMPROVE MY SUSPENSION?

Yes. Every time a wheel leaves the ground, engine rpm increases. The extra rev spins the rear wheel quicker, and when it hits the ground it is harder to control. The wildly gyrating rear tire bounces the bike around and works the suspension. With a flywheel weight, the rear tire can stay hooked up accelerating over choppy terrain. Over whoops, the tire stays closer to the ground and the bike reacts more smoothly to every hit.
QUESTION 14: WHAT ABOUT THE MUD?

Just like on dry dusty dirt, the slicker the mud, the easier the bike is to ride with more flywheel weight. Turning the throttle on results in a more manageable power delivery and more knob bite. The measured engine deceleration keeps the rider on the brakes much longer and harder.
QUESTION 15: HOW CAN I TELL IF I NEED MORE WEIGHT?

Most bikes work fine with the stock flywheel weight, but there are bikes that demand more flywheel weight. The classic examples are the Suzuki RM250, Kawasaki KX125, Honda CR125, KTM 250SX and Yamaha YZ450F.
Not surprisingly, many factory riders run flywheel weights on their race bikes. Why? Because they pump out as many as ten more horsepower. The flywheel weight helps tame those ponies.
QUESTION 16: WHO SELLS WEIGHTS?

Steahly, Zip-Ty, Terry and DR.D offer bolt-on flywheel weights or flywheels that have had more weight welded to them. The accessory divisions at Yamaha, KTM and Kawasaki also carry heavier replacement flywheels.

QUESTION 17: WELD ON OR BOLT ON?

It doesn't really matter. They both have pluses and minuses. A rotor that is modified with a weld-on weight can fit in tighter ignition cavities and is as reliable as a standard rotor. Weld-on weights have to be sent away to have the work done (or suffer core charges). Bolt-on weights are more affordable and seem easier to install (but it isn't always true, because some bolt-on weights require drilling).
QUESTION 18: DO BOLT-ON WEIGHTS FALL OFF?

When you bolt something on a wildly spinning crank that heats up in excess of 300 degrees, there is always a risk of something going wrong. Some bolt-on weights are only held on with two screws (others mount under the center nut and are kept from spinning with set screws). They can fall-off, but so can any other part of your bike that is held on by a bolt.
QUESTION 19: DO THEY FIT THE SAME ON EACH BIKE?

Bikes with less room under the ignition cover or with an internal or external rotor all take a different style of weight and mounting procedure. Weights for internal rotors generally bolt or weld to the exterior of the flywheel. On external rotors, the weights sometimes fit beneath the flywheel. On some machines, it's necessary to space the ignition cover outward to clear the weight.
QUESTION 20: HOW MUCH WEIGHT IS BEST FOR ME?

Most motocross riders end up running a 4 ounce or 8 ounce weight. Enduro riders typically run 8 ounce to 12 ounce weights. Most MXA test riders prefer the lightest flywheel weight that still offers the benefits of the weight.
QUESTION 21: DOES THE PLACEMENT OF THE WEIGHT MATTER?

You bet! Four ounces on the inside of the flywheel is not the same as four ounces on the outside of the flywheel. The farther the mass is located away from the axis, the greater moment of inertia. On most modern bikes, the exact position of the weight is controlled more by the limited available space than by a desire to tune the rotational mass. Only one aftermarket firm designs their weight by measuring the moment of inertia.
QUESTION 22: HOW DO THEY MEASURE INERTIA?

World Four-Stroke and Veteran Champion Doug Dubach is a fulltime test rider for Yamaha who just happens to own DR.D racing, which sells flywheel weights. When Dubach set out to design flywheel weights for DR.D Racing, he borrowed Yamaha's moment of inertia tester.
How does it work? A flywheel, with or without weight, is placed on a spinning platform. When the platform is wound up and released, an indicator counts how many times and how long the platform unwound and wound. Using a formula, the tester calibrates the exact moment of inertia of the flywheel.
A flywheel with more inertia will take longer to wind and unwind, but it will do it more times. Although the weight was picked by using the kilogram-centimeter squared (kg-cm2) measure of the moment of inertia, Dubach still advertises his weights by gram weights. A weight is still the number that is most recognized by riders.
The stock YZ45OF flywheel weighs 469 grams and has a moment of inertia of 3.6 kgcm2. Dubach offers his weld-on weight in 100, 150 or 203 grams (3.5, 5.3 & 7.2 ounces). Once welded to the stock flywheel giving a total flywheel weight of 569, 619 or 672 grams respectively-the moment of inertia is increased to 4.46 kgcm2, 5.27 kgcm2 and 5.98 kg-cm2.

Edited by MELK-MAN, 17 February 2012 - 10:15 AM.

MELK-MAN, on 17 February 2012 - 10:12 AM, said:

Great article

rpxtreme03, on 17 February 2012 - 09:09 AM, said:

Everyone responding to you realizes that a heavier weight will accelerate more slowly when being pushed by the same amount of power. I think we can all agree to that?

The disagreement was with regards to your statements that horsepower and torque are reduced by a heavier flywheel. The torque and horsepower numbers will be lower under acceleration, due to inertia, but the the net horsepower and torque numbers will be unaffected once the inertia is overcome.

If you were trying to explain to us that the numbers would be lower under acceleration you couldn't have done a worse job.

Edited by mkeeping, 17 February 2012 - 11:11 AM.

Rpxtreme...on my pw50 which do you prefer the green powerband or the red powerband

mkeeping, on 17 February 2012 - 11:10 AM, said:

that is exactly what I was saying.."under acceleration" is your real world riding nobody rides at constant rpms. You are either trying to pickup speed in a straight or slow down for a corner. Not ride around at a constant rpm.
I think idid a fine job getting my point across just nobody wanted to listen because they wanted to try proving me wrong when they were trying to prove me wrong on something totaly different than what I was saying

rpxtreme03, on 17 February 2012 - 11:50 AM, said:

hmmm.. is that your "FINAL ANSWER" on saying you didn't say heavier flywheels reduce hp? (see your direct quote i posted below from a couple pages ago, just to refresh your memory ) As someone pointed out to me in a chain thread "we all make mistakes" .. Grow up, learn, move on..

---------------------------------------------

rpxtreme03, on 15 February 2012 - 11:00 AM, said:

now in this post you do elude to the purpose of a heavier flywheel and state the rpms rise slower..but WE ALL KNOW THAT. If you could get a 250 2t race bike or 450 4t to actually HOOK UP in the dirt all the time when you give it full throttle, perhaps fewer people would use heavier fww in the woods and enduros. But ya can't. they spin, ALOT..
Just reading your posts i have serious doubts about your "thousands of motor builds" or that i "would be surprised at who i am".. but until ya post up what famous shop or rider your building for im reserving my right to that opinion..

rpxtreme03, on 13 February 2012 - 03:58 AM, said:

Edited by MELK-MAN, 17 February 2012 - 01:00 PM.

rpxtreme03, on 09 February 2012 - 12:28 PM, said:

you may have a drag racing on PAVEMENT background, but i'm giving you less and less credit for knowing much about racing dirt bikes in the DIRT. I WILL AGREE with what that article you posted contends, that under near perfect traction conditions for a car .. a heavier flywheel car may get the jump due to more energy in reserve just prior to dumping the clutch, and that the lighter flywheel car will catch and hold a lead as (all things equal) the lighter flywheel engine revs faster.. but at constant rpm, you do not loose hp or torque. FOR SOME RIDERS on motorcycles, under some conditions, the benefit of a FEW OUNCES of weight are a benefit.

holy shit dude i have said this time and time again i think the FWW are good in many casses but on the 250 4T(like what i ride) i feel they are a bad investment in most cases because you loose hp and the gains you make in traction are not (IMO) enough to compensate the hp lossed when your competeing against 250 2T as well. i'm not sure how many times i have to repeat this...that was my very original post on this thread. and since then all you have done is talked in cricles, twisting my words and taking things out of context to give you something to argue over...like i said befor YOU DO LOOSE HP WITH A FWW..you dont loose your hp at constant revs. you loose hp and torque when accel.

.. so your saying it's highly unlikely you will be putting a heavier flywheel weight or recluse auto clutch on your bike ?

I have scanned through these and I have never owned an auto-clutch, but as far as a fww goes I love them. I have an RM 250 and they have some of the lightest flywheels out there. I put a Steahly 12oz. fww on my bike and wow what a difference. The bike is like a freakin tractor, and the power is way more controllable down low. The power output is way more linear and I cant tell that it gave up anything power wise. I now truly compare its lug ability to that of my XR400, but my RM has great suspension and is light as they get. The front end is very easy to loft to clear obstacles(far easier than without fww), and the bike is a blast to ride in the woods. In fact I am even going to go down to a 47 tooth rear sprocket so I have a little more top end for open areas. Just my two cents

Let er buck if your still following this yes you will love a fww for harescrambles and I would opt for the auto clutch after you have ridden one to see what you think. You will give up no power with a fww and I wiil guarantee that you will like your results. Go with at least a 10oz. for the RM

jcat, on 17 February 2012 - 10:06 PM, said:

except for the fact that we already established that you do in fact give up power..

i still think its a good idea to run a fww i was just proving a point
the fwws are great for the woods bikes that are hard to control(mostly all two strokes and possibly some of the harder hitting 4Ts)
in many cases the little bit that you loose hp wise you will gain that back on a better control of your bike...i personly run a 250f that i dont feel the need for the fww.. i am already underpowerd compared to the 2t