Ducati Monster Forum

I have been contemplating installing a Nichols Flywheel on the bike this winter.  Loosing almost 3.5lbs of rotational mass seems quite appealing but what are the advantages/disadvantages of doing this?  Here is what I know so far:

Pros:
Less rotational mass
Much faster rpm gain
Much stronger engine braking

Cons:
Less forgiving with throttle inputs - you must be smooth

Any additions/opinions  are appreciated.

KNG
S2R800

if i remember right the rotational mass of the flywheel also affect the 'flickability' of the bike. less mass, less willing to stay upright so easier to throw into a lean. but wouldn't that affect the bike wanted to stand back up as well?

less engine braking. [thumbsup] less mass for the rear wheel to spin.

The gyroscopic force of the rotating mass resists changes to it's axis. Once overcome the mass assumes a new axis. Both sides of a "flick" (up and down) are affected by the rotating mass.

Actually, more engine braking.  The engine spins up faster.  But it also spins down faster when you let off the throttle b/c less rotating mass.  When the engine spins down more quickly, there is more engine braking.  You might be refering to wheel hop.  There is less wheel hop from a hard downshift because the engine will spin up quicker to match the wheel speed.  It actls like a poor man's slipper clutch.

Con:  possible stalling at low rpm. 

I installed one and a week later went back to stock.

The first problem I had was the bike became a lot easier to stall. I had to learn to give it extra revs when taking off or the engine would just putt out. Secondly, it increased vibration. I know this for sure because when I went top speed down the freeway the numbers on my speedo would be blurring to me, something I'd never seen before. And finally I really didn't feel it brought much of any benefit at all. I'm sure if I was a higher end rider it would, or if I rode on a track, but I'm not that. Mostly do city stuff so ease of use and comfort are more important than outright performance. And it's not like I need more performance. I still got a long way to go to catch up to the limits of what this bike can do.

Anyway, for what it's worth that's my experience.

I'm interested in this mod myself... any other opinions/reviews?

I have the DP one on my S4R, it certainly spins up quicker and I have not noticed any low speed problems. However most of my riding is done at speed on back roads little or no 'traffic'.
If you use your monster for 'sport' riding then a light weight flywheel might be beneficial, if your riding involves a large amount of city commuting then stay with the stock item.

Ahh! that makes sense! Thanks for clearing that up

Is that really so?
The mass that is forced to accelerate or decelerate is less, therefore the breaking is less w a lighter fwheel. W a heavy one you clearly feel more
weight has to be altered, especially in city traffic in 2nd-3rd gear were a lighter fw is surely smoother.
The engine surely revs faster up & down, BUT, is that really more engine breaking? ???

I don`t know the facts about this, just referring what it feels like to me.

Yeah, it is so.

When you say "mass that is forced to accelerate or decelerate is less..." it sounds like you have it kind of backwards on the decel side of things.  When you cut the throttle, it's the mass, or rather the inertia of that mass that controls the deceleration. 

The important thing to remember is if you cut the throttle, the engine wants to go slow but the inertia of the bike (flywheel in this case) forces it to keep going at a higher rate (For example, cut the throttle in neutral, it goes to idle speed.)  So the engine fights the bikes inertia, slowly slowing the bike down to the speed the engine wants to be at.

So, if you use a lighter flywheel, there is less inertia for the engine to fight.  It's easier for the engine to get to the revs it wants to be at i.e. it happens faster.  More engine braking.

I guess it depends on how you define engine braking. Since the engine spools up faster when you're on the throttle, some people view that as "less engine braking." Conversely, since the engine spools down faster when you're off the throttle, some people view that as "more engine braking." I prefer to view it as the latter, because I tend associate the term "braking" when you're OFF the throttle and slowing down.

As for my opinion, I have an 800 motor and I welcome the improved throttle response. If I had a more powerful motor (S4R), I would probably leave it alone. With a lighter one, you definitely have to be smoother when getting on and off throttle (I immediately noticed that the first time I lane split after installing the lighter flywheel).

Also, the Nichols flywheel is MUCH lighter than the stocker. I went with an MPL unit, it's a good compromise between the heavy stocker and the superlight Nichols.

Ya think?!?  Hehehe...

Had one in my M750i.e. CR and it was too light for the mass of the crankshaft and my *personal* tastes.  When I rode over a bump, the weight of my body shifting about caused an almost inperceptable change in the throttle.  Well, the engine responded to it and the bike lurched forward and needed to be kept in check.  So, for me, my tastes and my bike...  (translation: YMMV) the solution was a stock flywheel with some mass cut off of the perimeter.  $20 on Ebay for the flywheel, and another $25 at the machine shop to chuck it up and turn it down.  Result?!?  Perfect for me, and my bike!

There's an easy solution for low rpm stalling.  Avoid low rpm.  At all costs.  [evil]

Yeah, there's that...   ;D

Is there another option for low rpm stalling?

bump up the idle a bit and/or get your bike re-mapped.

I ran a Nichols 9 oz. on my 04-S4R.  I didn't notice much difference really. Yea, it revved fast, but it revved fast stock.

Idle may have to be turned up some though as someone else said earlier.

I've wondered if it's worth it on a S4RS/T. I've heard the s4rs/t cranks are heavier than on a 999 to begin with.

LA

I have the Nichols on my 04 s4r. Did it with an engine build so I can't tell you the difference alone but I never stall low speed.

lighter flywheel will give you more hp, less torque.  Generally they help you on the higher end, and hurt you in the lower end.  It will rev up quicker, the lighter flywheel results more engine braking

My personal experience with them:   I like only for one reason... If you find that the flicking of the throttle (or gas pedal with a car) for rev matching is not quite quick enough, then I like them... otherwise I find them not worth the money.   just my $0.02

Wait.... What?  Really?

I always suspected a LF would let you deliver more HP to the wheel (obviously no difference at the crank), but less torque?  How?

How?

sorry... at the wheel when talking about hp and torque.. not at the crank.

How hard is it to install?


edit* http://www.nicholsmfg.com/flywheel-inst.html
found instructions :)

thanks me!

Less engine breaking for the record, I've ridden with one for quite awhile now... I have an M620 w/ adjustable throttle lever which prevents me from stalling it...

Quicker rev-up happens

Same HP and Torque I believe, lol..

More flickability with less gyro force in the turns ;)

Because rear wheel dynos measure the rate of acceleration of the drum to measure horsepower.

If the engine and wheel accelerate faster it translates to more hp at the wheel.

Light wheels will increase the reading at the rear wheel also.

I had the stocker on my 620 milled down to about a pound and a half and I love the effect.  It's been discussed before that this mod really has a more noticeable effect on smaller displacement engines.  More flickable, quicker throttle response, and easier rev matching.  As for engine breaking, I think that the argument in this thread is based on the actual definition versus the perceived effect.  In any occasion... I like it better with the lightened flywheel. 

One of the downsides is that less weight in the flywheel will accentuate any inherrent vibratons or pulses that the engine may have.  Inconsistencies that the heavier flywheel would have otherwise compensated for.  The thing is... it's not the lightened flywheel that causes more vibes.  The idea is that if you experience more vibes after the lightened flywheel install, you should go after the actual problem that is causing the vibes.  Low RPM stalling is so easy to fix if it occurs that I didn't really even want to mention it.

Next to gearing changes and openieng the airbox, I think this is one of the best mods that can be done to a small displacement engine.

Best mod I have done to my bike (M1000).  Engine is more responsive.  Easier for smooth down shifting and lifts the front wheel easier!  Engine feels more powerful.  It stalls easier when cold but thats about it.  I had to have my idle speed slightly increased (back to 1,100 RPM) when I installed the flywheel.

But not at the crank, correct?

The crank is before the flywheel, so no affect to actual HP, just how it gets put down on the ground (the useful kind of HP)

Correct...

but you ain't riding a crankshaft bro. ;)

The increase is real world...

not sales hype.

Not having fiddled with my engine extensively (yet), could anyone recommend which parts of the stock flywheel to mill?  That sounds like a fairly cheap winter project to me  ;D

One more opinion on this over opinionated topic.    Think of the flywheel or any mass that has momentum (rotating or linear) like a bucket that holds energy, call it potential energy.   A lighter flywheel spinning at the same speed has less capacity for potential energy,  for this reason it spins up faster (accelerates) because it take less energy to accelerate it. Therefore for a given energy input (motor Hp) more energy is available from the motor to accelerate the bike faster.   The thing to remember here is a flywheel only resist acceleration and deceleration,  once its rotational velocity is constant mass does not matter for anything other than its gyroscopic effects.
 
If engine breaking is done through down shifting  the bike decelerates as the momentum is dissipated through the engine as friction (heat) PLUS is re-stored as potential energy within the engine's rotating mass as it accelerates due to energy transfer from the bike momentum into the engine's rotating momentum.    A more massive flywheel will add to engine's rotating mass causing it to resist acceleration even more.  This will lead to increased engine breaking but only as long as the engine is actually accelerating from braking.  He Man's first hypothesis.  But once it reaches a constant velocity during engine breaking the mass of the flywheel acts to decrease engine breaking because the additional stored energy must be dissipated through friction in the engine, Spidey's hypothesis .  In the end the mass of the flywheel within the range we are talking about has little effect on engine breaking because these factors tend to cancel each  other out.

 [thumbsup]
Bravo Ducnial! A very composed expose` of the dynamics involved with mass and energy. I tip my hat to your erudition on the subject matter. [clap] [clap] [clap]

You're assuming a downshift.  And you're basically saying the same thing I did.  A lightened flywheel will reduce wheel hop (or call it engine braking if you want) because it more easily matches the revs of the engine.  In practical terms, if you downshift, the bike won't slow down as fast (again, call it engine braking if you like), but the revs will skyrocket.  Thus, as I said, it acts like a poor man's slipper.  But if you just roll off the throttle without downshifting (real engine braking), the lightened flywheel is more responsive.  It will allow the engine to slow down faster.  In practical terms, the bike will slow down faster.

So, what do we know about lightened flywheels?  In practical terms, that is. 

1)  You can bang a downshift with less fear of locking up the rear.  The bike will slow less than bike with a stock flywheel until the engine catches up with the wheel speed.  Then it will slow down faster than a bike with a stock flywheel.

2)  If you roll off the throttle with a bike with a lightened flywheel, it will slow down faster than a bike without a lightened flywheel.

They don't cancel each other out.  In (1), you have two separate things happening at different times.  In (2), there is only one thing happening.

Spidey gets an A+ [thumbsup]

Spidey,

We are both saying the same thing.    If restating it a differtent way helps others [and me] understand the physics of this topic,  that's OK.     You are right I was assuming only down shifting vs rolling off the throttle.  However we'll just have to agree-to-disagree on the issue of total breaking effect of  light vs heavy flywheels.   As you said, a stock flywheel will slow less than a light one during engine spin-up from a down shift  and slow more than a light flywheel as the engine catches up and breaks the bike from friction. If you treat these two phases together as total engine breaking  then there is no difference between light vs stock. E.g. comparing a light flywheel to a heavier one will flip-flop these relationships netting identical braking.  [assuming the contribution to braking from each of these two phases are the same, which they are not.]  I agree a light flywheel will reduce wheel hop, that's good, but probably wont make much of a difference total engine breaking within the range of weight we are talking about.

My Brain Hurts..  [bang]

boobies

My uncle, who's a farmer, pulls a plow with an tractor that's too small for the # of spades on the plow and the amount of clay in the soil.  He had too many instances where the tractor would bog down in certain areas of the field.  His fix was to place a HEAVIER flywheel on the tractor.  It definitely takes longer to get the tractor's rpms up to speed but once he's there the tractor pulls like a uh well a bigger tractor.  He ended up doing the same mod to one of his trucks he uses primarily for pulling a gooseneck trailer.

Of course he's trying to accomplish something different but its interesting to see that in some applications heavier better than lighter.