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View Full Version : Lightening flywheels? Advice please?


Muzz67
29th January 2007, 20:25
Newbie poster here. Standard flywheel rotor on my XR 500 is 2.250kg, and I am currently using a 250 one which weighs 2.050kg. The .2kg makes a considerable difference, and I am interested in lightening one further. Perhaps another .2kg?? Anyone tried this?? or any other suggestions appreciated too. Cheers!
DEATH_INC.
29th January 2007, 20:33
Tricky, they don't rev too much so prolly ok to machine it....What about a 200 flywheel and pickups etc? will they work?
Another option if she's an off roader is loose the balance shaft (if it's got one). We did this on my brothers old XT250 and it made a huge difference, but the old girl definately vibrated heaps more......usta put ya feet to sleep if you did a long road trip.....
Muzz67
29th January 2007, 20:55
200 totally different system, sadly. Balance shafts essential in the 500's. Have ridden a 250 without shafts and did not like it at all!
Brian d marge
30th January 2007, 01:08
Newbie poster here. Standard flywheel rotor on my XR 500 is 2.250kg, and I am currently using a 250 one which weighs 2.050kg. The .2kg makes a considerable difference, and I am interested in lightening one further. Perhaps another .2kg?? Anyone tried this?? or any other suggestions appreciated too. Cheers!

thats pretty heavy BUT its there for a reason, flywheels store Energy the heavier it is the slower it will accelerate, and decelerate ..ie change energy states

it wont increase /decrease power ,,etc ... Soooo the question is what riding do you do ...if its trail and enduro ,, heavy is good .. ( try feathering a light 2 stroke through a tricky section ,,with a light flywheel and it will/can switch off like a light

the reverse is also true

Stephen

I made my own flywheel for the cr and didnt go heavy but taller ,, as its the radius of mass , ie the point where the flywheel effectively carrys its wieght ,,so a light but large dia, can be the same /better than a small heavy one
Muzz67
30th January 2007, 06:03
a set of road wheels for Motard too, so almost all of its use is in the middle to upper end of the rev range. The 250 rotor has made if spin up quicker and it still pulls like a schoolboy right off idle speed, so I thought even less would be even better. I guess there is a point where too much off would be a bad thing though. Cheers!
Brian d marge
30th January 2007, 13:13
The energy in the fly wheel is also used to keep the piston moving through the part of the cycle when there is no combustion input ,

The power will remain the same ,,ie pull like a school boy BUT there will be no energy in the flywheel so it could stall easier.

So long and short, yes you can go light ,,,, the only things that could happen will be it will be a Bitch to start and vibrate like a goodun(the lighter you go )

Stephen
NordieBoy
30th January 2007, 18:18
Ask Shane how much he got machined off my 250 one.
Brian d marge
31st January 2007, 02:08
How much shane???

Stephen
NordieBoy
31st January 2007, 08:13
How much shane???

Ummm...
Just enough to make a brother.





With some left over for a beer gut.
Muzz67
31st January 2007, 19:25
Has he fitted it to your current XR or is it for the new engine? Wondering if I could borrow it!?
NordieBoy
31st January 2007, 21:03
He skimmed down the one on the bike.
We had another to try but it was off a 12V version.
Like you said - Much better pickup and engine braking but not too much loss of traction on the big hills.
Muzz67
8th March 2007, 19:05
Here ya go Fran, Ruapuna.
https://secure.sportzfotoz.co.nz/popimage.php?imageid=6078
NordieBoy
8th March 2007, 19:10
They even let you on the track?

Apart from the leathers that dosn't even look like an old bike :D


And from the photography point of view, they could have waited half a second and got a decent pan shot :D
Muzz67
8th March 2007, 19:29
Yeah, the scrutineers had a good laugh at the leathers!!They're pbobably older than me, and all I got now is grey hair.
The old XR did bloody well, scraping footpegs most corners. Easy to outbrake big road bikes, or ride around the outside of them. Got absolutely wasted on the looong front straight though!
https://secure.sportzfotoz.co.nz/popimage.php?imageid=6169

Heres Phil on CRF
https://secure.sportzfotoz.co.nz/popimage.php?imageid=6169
NordieBoy
8th March 2007, 21:43
The CRF looks just like your bike :D
Muzz67
9th March 2007, 06:04
Aw crap. Should really learn how to cut'n'paste properly.
This aint Phil either.
https://secure.sportzfotoz.co.nz/popimage.php?imageid=6358
idleidolidyll
9th March 2007, 06:53
not the flywheel per se but i machined 1kg off the clutch assy and drive pinion on my old 2001 900ss Ducati.

That was a revelation, unleashed the beast. Being a 90 degree Vee it didn't seem to make any difference to torque/inertia