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Eddieb
5th February 2004, 16:06
Anybody done it?

Does it really make such a difference to how fast the motor spins up, how does it effect performance, what does it cost, etc, etc.

duckman
5th February 2004, 16:21
Anybody done it?

Does it really make such a difference to how fast the motor spins up, how does it effect performance, what does it cost, etc, etc.
Never done it myself, but as I understand it, with a lighter flywheel theres less weight to spin and so it revs up quicker.

Much the same argument as replacing stock wheels with lighter ones... I think it's called "unsprung weight".

Give it time and someone with some technical knowledge will reply. :D

Big Dog
5th February 2004, 16:21
Anybody done it?

Does it really make such a difference to how fast the motor spins up, how does it effect performance, what does it cost, etc, etc.

Yes, most factory setups are done with constant speed in mind. The objective is to smooth out the acceleration curve.

The whole ides is to give you less need to adjust your throttle position to maintain a speed.

The upshot is your bike will accelerate better but will require quicker reactions to such things as bumps and hills.

You will find more wear on chain and sprockets (and your neck) but draggers do it because it can shave 2 seconds off a 1/4 mile. Expect it to be one of the cheapest performance mods (depending on model some are harder to get at / some already have custom parts available), but expect the costs of maintenance to go up. Had it done to a car. No change to hp but it halved the time to get up to 100kph. Sparks needed cleaning/changing more often (as the amount of fuel being burnt changes faster than the supply of fuel can), and my tranny suddenly felt "looser".

For how I was driving it was good but it rendered my car incappable of safe towing as it lurched too much. :eek5:

Big Dog
5th February 2004, 16:28
Much the same argument as replacing stock wheels with lighter ones... I think it's called "unsprung weight". :D

I may be wrong but I'm pretty sure your referring to mass displacement. Unsprung weight refers to weight that is below the shock absorbers and the suspension set up itself.
It refers to weight that if you pushed down on it whilst it was stationary on the ground would not move.

Mass displacement refers to the amount of mass your motor needs to move before any power is applied to the ground. Ie pistons, transmission, flywheel, crank, chain, cush, back wheel, rear brake, tyre, clutch etc.

duckman
5th February 2004, 16:31
I may be wrong but I'm pretty sure your referring to mass displacement. Unsprung weight refers to weight that is below the shock absorbers and the suspension set up itself.
It refers to weight that if you pushed down on it whilst it was stationary on the ground would not move.

Mass displacement refers to the amount of mass your motor needs to move before any power is applied to the ground. Ie pistons, transmission, flywheel, crank, chain, cush, back wheel, rear brake, tyre, clutch etc.

Oh shuddup, i was just starting to sound intelligent!! :sly: (not likely)

Thanks Big Dog - I learn stuff everyday from this site. :rockon:

Big Dog
5th February 2004, 16:58
Oh shuddup, i was just starting to sound intelligent!! :sly: (not likely)

Thanks Big Dog - I learn stuff everyday from this site. :rockon:
Wait...... wait...... someone is bound to shoot me down if we wait long enough. :Pokey: :eyepoke: :kick: :bleh:

Kwaka-Kid
5th February 2004, 17:44
from what im told... im loosing flywheel completely on the racebike which on a 53hp 400 gives me another 2.5hp, and helps the bike rev faster, but looses a bit of torque and smoothness... i figure that i already have slightly more torque then others being on a V4 not inline4, and that has helped my racing as its easier (more broad power curve) but as i get better/more experienced i can deal with a smaller but higher bang of power sort of thing, i dunno, plus im bored and just wanna do muck around free-mods to the bike! :D -personally dont know if its worth bothering to lighten, just take it off all together, its All or nothing my friend!

wkid_one
5th February 2004, 20:16
Now coming from my big boy racers days - I had a lightened race flywheel in my VR4 EVo and it makes a huge difference to how quickly the engine spins up - but be warned it can equally affect to ability of the vehicle to pull up hill......

Also - it can weaken the flywheel to the point whereby you need to replace it more often....and can lead to more money having to be spent on other items of the clutch assembly and drive train.

If you think about the whole drive train as a balancing act - if you add or remove certain elements to it - this can create or remove stress from other items within the system. For example - cars with improved clutches etc often shit the selector fork as this is the next weakest link.

I also had a triple plate clutch etc etc etc. About $12k invested in the drive train.

Just something to bear in mind is that upgrading one part - often means upgrading another

The exhaust is another common one.....manus spec the mapping to run off a set airflow in and out....change the airfilter and you need to do your jets or or or or or.

Flywheel changes are great - but only consider if you are looking to do the whole drive train......otherwise the changes can be more detrimental than beneficial.

wkid_one
5th February 2004, 20:20
I may be wrong but I'm pretty sure your referring to mass displacement. Unsprung weight refers to weight that is below the shock absorbers and the suspension set up itself.
It refers to weight that if you pushed down on it whilst it was stationary on the ground would not move.

Mass displacement refers to the amount of mass your motor needs to move before any power is applied to the ground. Ie pistons, transmission, flywheel, crank, chain, cush, back wheel, rear brake, tyre, clutch etc.
You are right - unsprung weight is everything that is not suspended by the bikes suspension.

The flywheel is actually referring to the principal of inertia - the lighter something is the less energy is needed to get it moving. Therefore if you expend the same energy moving something lighter - it will move quicker.

wkid_one
5th February 2004, 20:25
Much the same argument as replacing stock wheels with lighter ones... I think it's called "unsprung weight". This has alot to do with gyroscopic forces also - and the weight something has when spinning.....the less weight the less gyroscopic force - there the easier it is to alter direction.

Pilots artificial horizons work with a 'gyroscope' - which is essentially a spinning disk spinning within a freely moving frame - this will always stay in its original orientation, therefore regardless of what way the plane moves - the gyroscope (artificial horizon) will remain in the same place.

A bikes wheel is the same - once spinning - it takes a lot more force to make it change direction as it doesn't want to change - and this increases as the speed of the spinning increases. Which is why is it easier to change direction the slower a bike is going. If you therefore reduce the unsprung weight - you in turn reduce the mass of the gyroscope - which in turn means you can change direction easier.

wkid_one
5th February 2004, 20:27
Please disregard my 'physics' as I have just come back from dinner and am slightly inebriated.

Racey Rider
5th February 2004, 21:03
Removed: No longer relavent

duke
6th February 2004, 06:43
I lightened the flywheel and removed the alternator on my racing Pantah last year. It's made it easier to keep on the redline and I've not noticed much loss of momentum at low revs. I've only used the bike on the track and think it was a worthwhile performance mod. The flywheel mod might be worth considering for the road if you don't need to do much stopping/starting and you red-line a lot
regards
duke

merv
6th February 2004, 08:49
:D -personally dont know if its worth bothering to lighten, just take it off all together, its All or nothing my friend!

I doubt you'll be able to do that as it more than likely actually makes up the alternator on your bike i.e. the magnet thingy spinning round the coil thingies and it will have the ignition timing sensor and stuff like that on it too. You'd have to be prepared to replace some of that stuff with some race kit gear instead, can't just take it off and throw it away. Duke talks of taking off the alternator and if you did that the bike would have to be set up to run off battery alone.

Also it is unlikely that no matter how light your flywheel that it will allow the engine to generate more peak power - as has been mentioned by others it would allow the engine to pick up quicker i.e. the power and torque will remain the same, the inertia they have to overcome is what is less, but once you're up to peak power revs and it aint accelerating much more it can't magically produce more power from somewhere. However, if you can remove the alternator you will recover the power required to drive it - not sure that would be 2.5hp though. Otherwise change has to be made to make better action inside where it happens i.e. boost the action in the combustion chambers - higher compression, better beathing, better carburetion, cam profiles, exhaust system or whatever.

I wouldn't be surprised that there aren't too many useful grams that can be shaved from your flywheel to make it go any better. The V4 should have inherently less inertia in the first place - shorter crankshaft less bearing friction and mass etc, but hey no harm trying but seek advice (probably internet search for engine mods) and don't just go for the doctor first off.

Kwaka-Kid
6th February 2004, 09:50
for sure merv, and yeah not so good on a street bike, but im cutting my whole loom right down and running a total loss system. Well the guy who told me i trust has he has a fully worked RVF400 that has had shitloads done to it back in Wales, and was put on the dyno and apparently alone, that loosing the flywheel (and alt etc) gave a 2.5HP increase, apparently the biggest engine mod you can do for free. -i trust the guy, and his bike just f***s off when we line up to nail a straight :(

gpercivl
6th February 2004, 11:12
Lightening up the flywheel does improve the peak horsepower output of the motor and allows it to gain rpm more quickly but at the cost of losing a little mid-range.

My F2 bike runs Yamaha race kit ignitor and pickup which has very little mass compared to the alternator pick up it replaced...it also originally had the starter motor gear removed off the other end of the crank. The motor was very peaky and in an effort to get some mid-range back we put the starter gear back on...this lost 1 to 2 hp on the dyno, but did improve the mid-range.

A lot depends on your riding style...Dave Cole who originally raced the bike use to keep it spinning at max revs everywhere, whereas us more mortal plebs prefer to have the revs a little lower coming out of corners so the mid range is of benefit especially on NZ race tracks having relatively slow corners and short straights between.

Motu
7th February 2004, 07:15
If you are using an inertia dyno,which is what most bike dynos are - then yes you will see a HP increase...if you put it on a brake dyno,eddy current or the combos that are around,then no,you won't see a HP increase.An inertia dyno,or incar computer dyno measures acceleration and computes HP from that,if your bike accelerates better then it deems it has more HP,this makes you happy,but in reality no HP has been gained.

Racey Rider
8th February 2004, 17:32
Side issue:
I having trouble getting the flywheel off my KR150.
I have taken both engine covers off, and placed sockets on both sides, but only the nut on the cogg (Clutch side), wants to undo.
Any tips?
Flywheel nut isn't reverse thread is it?

Racey

Big Dog
9th February 2004, 16:30
Side issue:
I having trouble getting the flywheel off my KR150.
I have taken both engine covers off, and placed sockets on both sides, but only the nut on the cogg (Clutch side), wants to undo.
Any tips?
Flywheel nut isn't reverse thread is it?

Racey

That would be locktite on yeah? I suggest application of a hammer to the end of the bolt to break the locktite. :sweatdrop

merv
9th February 2004, 18:52
Have you got an impact driver and a socket that fits it?

Racey Rider
18th February 2004, 20:58
Still having trouble getting this flywheel nut off.
Have been attacting it with impact driver and socket but it won't undo!
I am thinking of getting a butane torch to heat it up before trying again.
Will the heat transfer ruin any seals or anything along the crankshaft?

Dave
19th February 2004, 13:44
Yes- that would wreck the seals. Have a look at the exposed end of the thread and see if its left hand-it may be.Assuming that its not, Then put the bike in gear and get someone to stand on the rear brake. Get a power bar or large ratchet and pipe and undo it.Once you have the nut undone- you still may need a special puller to get the flywheel off,Most of these are on a taper and need a puller to remove.
Maybe a local bike shop would lend you one if you ask.

speedpro
20th February 2004, 21:41
I've removed a flywheel, actually the alternator rotor, from a race bike and the differance was great. The motor revved a lot faster, up and down. One big benefit which noone seems to have mentioned was that when piling into a corner and snapping down a few gears, because of the reduced inertia the tendancy to lock the rear wheel was reduced a lot. This is due to the ability of the motor to rev quickly to match the new gear and if the rider doesn't quite get it right then the reduced inertia has a reduced effect. It doesn't actually give you any more power except what the generator might use, say <300W, but as mentioned it may indicate a bit more on an inertia dyno.

I may be wrong but I just do not see how arranging cylinders into a "V" configuration or an inline configuration can alter an engine's power characteristics if everything else is the same. The probably lighter crank and fewer bearings could affect response but the power/torque produced at any revs should be the same if the cylinders, valves, cams, etc are the same.

Kwaka-Kid
20th February 2004, 22:26
yeah speed you do sound right... but its just what everyone seems to say! and yes they mention shorter crank etc, umm, yeah well i will hit some of these people up on this. but even in WSBK years ago when the RC45 was in, they were only aloud 750cc V4's, yet 1000cc inlines wasnt it? maybe im wrong there too actually, hehe who knows, all i know is people say the V4's make more torque then the inlines :S

Kickaha
21st February 2004, 07:07
I may be wrong but I just do not see how arranging cylinders into a "V" configuration or an inline configuration can alter an engine's power characteristics if everything else is the same. The probably lighter crank and fewer bearings could affect response but the power/torque produced at any revs should be the same if the cylinders, valves, cams, etc are the same.

Had this same argument on another website,if all those things are the same,there really shouldn't be any difference in the power delivery.


We lightened the flywheel on one of my bikes with the same results as speedpro and bikes that coud previously out accelerate me were no longer able to,at the moment we have a crank in being lightened and we are ditching the flywheel all together and just building a trigger wheel for the ignition.

DEATH_INC.
21st February 2004, 07:16
yeah speed you do sound right... but its just what everyone seems to say! and yes they mention shorter crank etc, umm, yeah well i will hit some of these people up on this. but even in WSBK years ago when the RC45 was in, they were only aloud 750cc V4's, yet 1000cc inlines wasnt it? maybe im wrong there too actually, hehe who knows, all i know is people say the V4's make more torque then the inlines :S
Na,it was 750 fours (of any config) or 1000 twins.....
Lightening the flywheel will work great.Have a look at smaller capacity bikes similar to yours,you may find something smaller/lighter that will fit straight on without mods......I've done this on my Turbo.
The flywheel weight argument has been around for ages,In nascar for example some guys use real light one's,favouring the quicker response,and others use a heavy wheel,helping smooth power and maintain momentum.Same with drag racing,sometimes with a less powerful engine a bit of flywheel weight will give you a better launch,helping to stop the engine bogging when you drop the clutch.

DEATH_INC.
21st February 2004, 07:37
I may be wrong but I just do not see how arranging cylinders into a "V" configuration or an inline configuration can alter an engine's power characteristics if everything else is the same. The probably lighter crank and fewer bearings could affect response but the power/torque produced at any revs should be the same if the cylinders, valves, cams, etc are the same.
The main reason is because it alters the timing between the power pulses.A few of the manufacturers have played around with this.Yamaha's TRX850 for example (a parallel twin) uses a 270deg (I think)crank spacing to trick it into thinking it's a 90deg v-twin.Same with the RSV aprillia,a 60deg v-twin that thinks it's a 90deg v-twin because of the crank configuration(that's why they don't sound like a Hardley).Honda too experimented with the VFR400,changing it from a 180deg crank to a 360deg crank which as anyone who has ridden the nc24 and nc30 will tell you altered the power characteristics heaps.
And a few of you old guys :whistle: will remember the old f5000 days when they played around with flat plane cranks in the V8's to get a little more power.....

Motu
21st February 2004, 09:06
Anyone who heard the Guzzi V8 last year would of been disapointed because it didn't sound like a ''real'' V8,that was the 180 or flat plane crank,it's the 90deg crank that has the yank tank sound.

The V twin staggered firing impulses giving traction has been known to the American flattrackers for a long time - the off beat impulses and a declining torque curve give great control in low traction situations,with so much power on tap with superbikes etc it has become the hot set up.My 45 deg Honda engine had a single pin crank for dirt track but a staggered 90 crank for street use - one sounded like a Harley,the other like a Ducati.

wkid_one
21st February 2004, 10:08
Same principal goes for the Duke big bang motor in Gp as opposed to the traditional firing of the multis. It is all about trying to find different ways of doing the same thing better (like sex I suppose).

Like the rotary engine for the Lambo that the Kiwi designed. Just about trying to overcome the natural physics of a combustion engine to make it more efficient.

Kickaha
21st February 2004, 13:19
The main reason is because it alters the timing between the power pulses

Well that could be done with any engine,doesn't have to be a V motor,its all to do with the crank phasing and firing order.

As an example a friend of mine with a TZ250 superkart running a 89 reverse cylinder engine has a 180 degree firing order and is quite a peaky motor,as an experiment he rephased the crank to a 90 degree firing order like the later V twin,changed ignition etc and then ran it,completely different sound and power delivery was then more like the V twin and a lot more driveable.

speedpro
21st February 2004, 20:31
he rephased the crank to a 90 degree firing order like the later V twin,changed ignition etc and then ran it,completely different sound and power delivery was then more like the V twin and a lot more driveable.
If the BMEP stays the same for each cylinder I still can't see how having them arranged differently could affect the measured power. I think the relevant bit is that the ignition was changed. This could have significant effects on the power curve

Racey Rider
22nd February 2004, 18:49
... Have a look at the exposed end of the thread and see if its left hand-it may be.Assuming that its not, Then put the bike in gear and get someone to stand on the rear brake. Get a power bar or large ratchet and pipe and undo it.Once you have the nut undone- you still may need a special puller to get the flywheel off,Most of these are on a taper and need a puller to remove.

WHAT A SOD this nut is!!! :angry2:

Yes the exposed end shows it's a normal thread. Have tryed both ways anyway.
Impact driver won't move it. So then I tried your idea. Ended up with a piece of wood through the mag wheel and onto the swing arm. No way that wheel was going to move. Then engaged first gear and got the socket/rachet onto the nut. Once the wheel was holding presure against it, I could turn the rachet 180 degrees before needing the bit of pipe added. Once the pipe was on, it keeped turning another 180 or more degrees, adding more presser on everything the more I pressed. I knew the wheel wouldn't move, so something had to give! I was in fear of breaking gearbox cogs, when something gave.
First I thought the nut has come loose, but no. The clutch must have slipped.
Happened a second time, so I gave up!
I do have 2 sets of pullers, so once I get this flippen nut off i should be right.
Guess I'll just have to use the heat treatment, and replace seals and,,,, the whole motor if need be!!

Any other ideas?? :spudwhat:

I wanted to get this flywheel off before removing the motor from the bike for repair. :confused2

Racey.

speedpro
22nd February 2004, 19:55
Buy a rattle gun. Even a little one from somewhere like Partmaster should take it off no problem. You will need a special puller to get the rotor off. They are available in a lot of bike shops and made by Buznatti or something like that. They're only $20 odd so pay for themselves in no time. If you look at the rotor and the nut holding it on you should find a large diameter fine pitch thread on the inside of the rotor where the nut is, the tool screws into that and presses on the crank once you get the nut off. These large threads can be left or right handed and come in a few different sizes but the shop should know what size you need.

If you don't want to fork out for the rattle gun you can take the head and barrell off and put a screwdriver handle between the flywheels so that when you try and turn the nut the big end of the rod gets jammed against the screwdriver handle which will be jammed against the crankcase. I've done this lots, I'm a bucket racer, and have never caused any damage.

Racey Rider
25th February 2004, 19:20
:banana: :banana: :banana:

It's OFF!!

Gotta get me one of those rattle guns!

Found a friend of a friend with one. Took him all of 2 seconds to get that flywheel nut off. :banana: :2thumbsup :banana:
So, flywheels off, motors out, can't wait till the weekend to get the barrel off and into the next stage of problems to solve. (What was that ticking noise in the motor?).

Thanks to all who offered suggestion!

More questions next week for sure!

:rockon:
Racey

Dave
26th February 2004, 12:25
How embarrasing for you. The method i described is what i have used for years to take off bolts that are too tight for a rattle gun.
You must not have had any weetbix this week.

DEATH_INC.
29th February 2004, 08:31
Well that could be done with any engine,doesn't have to be a V motor,its all to do with the crank phasing and firing order
Yeah,like a TRX850.....