Whats the deal with lightening and balancing flywheels?
We don't seem too hear much about it here, but on US websites, it seems thats the first mod a lot of them intend to make, going on about the engine spinning up quicker.
From memory on here yes they help the engine spin up quicker (pro) how much I don't know, but the con is that at low revs/tickover etc the bike becomes hard to ride, needs a good handful when moving off etc
There are probably quite a few other pro's and con's and no doubt they'll be more replies and a hugely indepth one from Nelly/Shazaam!
Lighter flywheel lets the revs build and die off more quickly. It will also probably mean you will need to raise the tickover otherwise it will stall. Does improve acceleration, both from a start and for overtaking.
The American sites do go on about idling and stalling issues, but there are others who say that this is purely down to a poor state of tune. As for me...I haven't got a clue!
Mines got a lightened flywheel as standard...and yes it can be a little lumpy at tickover due to reduced mass (and in my case lumpy cams!) and until it has been running for perhaps 10 mins it can stop on you when at tickover. Often catches me out at the first few junctions from my house! But once up to temp its fine.
Difficult to tell how quicly it spins up as it was fitted when I bought it...but it certainly does feel very free reving.
As for the comments about poor state of tune...I think it depends on the bike...if fitted to a Bip or S model then I think it should be able to run fine...with the R or SP(S) models, due to their higher engine specs (compression etc), they may become a little more vulnerable to the engine stopping etc when ticking over.
Forgot about that side of things Monty, as you've got a lighter flywheel there's less inertia so revs rise quickly and die quickly, so great acceleration and more engine braking
If you have an (999) S, don't bother, it already runs a lighter flywheel as stock. Not as light as some people run, but never the less its a few hundred quid for marginal gain on that particular model assuming street use is intended.
When my 999s was being fettled by Sigma Performance we discussed fitting a lightened flywheel when the motor was in bits and decided it was more beneficial to spend the money on something else. The weight saving on the flywheel was only a few grams. The wallet lightening however was considerably more!!
my Baby R had one fitted when the kit was put on and it certainly does pick up and drop very quickly. However tickover had to be set at 1800 rpm to get it to tick over-not a problem but quite difficalt to get off the line as JPM says. Butch
31-May-2005, 17:56 
Monty
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