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Hi all,

I've managed to sort a new engine for my bike from Steve P, picking it up next week hopefully into which I need to put my sprag clutch (which is pretty new). I've half thought about putting in a lightened flywheel while its stripped. Has anyone done this? Pros and cons? As I understand it, it wouldn't really provide more HP but would allow the motor to spin up quicker and hence, improve acceleration. That with my 15t front sprocket should make life interesting.

Any thoughts? Got to source one yet like.

Cheers

Paul.

No experience but:

* Would it be a bit more "lumpy" / "vibey" ?

* Would it tick over less smoothly or require a greater tic over speed?

Not sure - just speculation

.... and doesn't a heavier flywheel = more torque ?

Reducing the flywheel mass will mean the engine is more prone to stall at low revs. The engine will "spin up" and slow down more rapidly.

My experience is that the engine as standard, is a little prone to stall if pulling off on minimum throttle, something I do need to do on a regular basis because of the noise factor. The engine also spins up very very quickly anyway. If the flywheel was very reduced I think it would also put extra load on the big end and main bearings. I think the Rotax has a very little flywheel effect but then I'm used to Guzzis and BMWs.......

It will not increase or decrease the torque but less energy goes into accelerating the fly wheel so more into what is attached... .but marginal stuff unless you are talking Kilo’s not Grams. My summary is it is a worthwhile thing to do on an old Guzzi or an old boxer twin that you want to make a bit sportier but not on the Rotax.

bigun wrote:Hi all,

I've managed to sort a new engine for my bike from Steve P, picking it up next week hopefully into which I need to put my sprag clutch (which is pretty new). I've half thought about putting in a lightened flywheel while its stripped. Has anyone done this? Pros and cons? As I understand it, it wouldn't really provide more HP but would allow the motor to spin up quicker and hence, improve acceleration. That with my 15t front sprocket should make life interesting.

Any thoughts? Got to source one yet like.

Cheers

Paul.

General concensus over at AF1 where a good number of em have removed the flywheel (you'll need a special tool from Aprilia, lots of heat and a damn big strong puller as well by the way) is that it isn't worth doing. Even Amauri who races Milles hasn't bothered with his own bike.
There are a number of reports about the threads being stripped out of the flywheel because Aprilia use so much Loctite green on them (and then don't bother using any at all on the sprocket bolt or any grease on the suspension linkages eh!!) so take cars if you do it because if the threads strip your in a whole world of bother

Those who have it say the benefits are minimal , the engine revs up a bit quicker etc..but you do loose 2lbs of useless metal off the bike after all!

Its not on on my list of things to mess with though

F9

Interesting replies, thanks. Might just leave it then! Saving 2lb when I'm 6ft7ins and 20 stone of rugby player seems a little fickle!

On the puller Rich, yeah, I've seen all the horror stories too but the puller has since been replaced by a modified version alledgedly. I'm ordering the puller and the engine locking bolt from Speedaway this week (£19 for both). Would have paid double to be honest as I'm a great believer that having the right tool makes life easier. That and a lot of heat and Pierres garage and it'll be sorted!

Paul.