520 conversion - loose front sprocket?

[kevin_stevens]

Just finished installing a Driven 520 conversion kit on my 2001 S3. Steel sprockets, 18/45T. Everything went very smoothly - incredibly smoothly considering what I've had to go through to change sprockets/chain on other bikes. Until the end, of course!

The front sprocket, being a 520 instead of the OEM 530, is of course narrower. It's enough narrower that the countershaft nut bottoms on its thread before taking up all the slack. It is torqued properly and the tabs fitted, but the sprocket still has around 1/32" play in which it is "floating" on the countershaft.

Is this normal for a 520 kit? I've had Ducatis with floating sprockets before, but the stock one on the S3 was clamped. I'd think that this was a common issue on 520 conversions for all bikes, and if it was necessary Driven would have shouldered the front sprocket, or included a washer/spacer that would have allowed a tight clamp.

I will call Sprocket Center and/or Driven in the morning, but wanted to get a read from the forum. Tx for any info!

KeS

[chopped knuckles]

Why did you change to a 520 chain , what is the advantage.???
As for the loose sprocket , it should be tight.the nut is not designed to stop on the thread, and the sprocket will fret on the splines if left loose. fit another spacer/washer under the nut against the sprocket.

[blastap]

you will need to find a hardened spacer to afix your sprocket correctly

[kevin_stevens]

Originally Posted by chopped knuckles

Why did you change to a 520 chain , what is the advantage.???
As for the loose sprocket , it should be tight.the nut is not designed to stop on the thread, and the sprocket will fret on the splines if left loose. fit another spacer/washer under the nut against the sprocket.

520 conversions have two benefits and one disadvantage. The primary benefit is a reduction in rotational inertia; the same effect you get in lightening everything from the flywheel to the clutch to the wheels. The secondary benefit is a minor reduction in unsprung weight; the chain and rear sprocket are considered "semi-sprung".

The disadvantage is that the chain and sprockets are not as strong. This can be mitigated by choosing a chain brand/model that is stronger for its size than OEM; though typically you can expect somewhat poorer chain/sprocket life.

It's most commonly a racing conversion, and the only reason I did it on the S3 is that a friend with one reported some significant improvements (and I needed a new chain/sprockets anyway).

I'll source a washer tomorrow - they're actually called something different when they are of that large a diameter, it escapes me at the moment. It's quite odd that Driven didn't handle it, though.

KeS

[wavrdr]

I used a large washer...I did have to enlarge the opening to fit the shaft though...

FWIW, I lost nearly 6 pounds of rotational mass when swapping to a 520 kit, and most of it was in the chain itself. I'm running a Driven front 18t, a Vortex rear 45t, and a DID 520 ZVM2....The bike is an animal now in conjuction with my other mods....

Good luck!

[chopped knuckles]

Originally Posted by wavrdr

I used a large washer...I did have to enlarge the opening to fit the shaft though...

FWIW, I lost nearly 6 pounds of rotational mass when swapping to a 520 kit, and most of it was in the chain itself. I'm running a Driven front 18t, a Vortex rear 45t, and a DID 520 ZVM2....The bike is an animal now in conjuction with my other mods....

Good luck!

Do you mean that thr 2 new sprockets and chain way 6 pounds less than the old ones ?

[Tripped1]

Originally Posted by chopped knuckles

Do you mean that thr 2 new sprockets and chain way 6 pounds less than the old ones ?

Very possible.

The Steel Sprockets are heavy as are the original DID O-rings the bikes came equiped with. I lost 3 lbs going from the stock DID O-ring chain to an XS series RK x-ring, and I stayed with the 530.

At one point I was standing there with a chain in each hand gong..."man, there is a difference here".

[chopped knuckles]

Originally Posted by Tripped1

Very possible.

The Steel Sprockets are heavy as are the original DID O-rings the bikes came equiped with. I lost 3 lbs going from the stock DID O-ring chain to an XS series RK x-ring, and I stayed with the 530.

At one point I was standing there with a chain in each hand gong..."man, there is a difference here".

I find that hard to believe as I just weighed my old original chain and it weighed in at 5 lbs so to loose 3 lbs I would need a 2 lb chain which sounds like a push bike chain.A Trials bike chain has no O-rings therefore the pins are shorter , saving weight and the plates are thiner 1.5mm instead of 1.8mm also saving weight.But I think I will leave the Trials chain on the Trials bike.The O-rings also create more friction and therfore drag, a reason why the dont use them on the Trials bikes.In this country if you change from original in your drive train then you require an engineers report or else it is not legal, which doesnt seem to matter untill someone gets hurt !Litigation.

[wavrdr]

I just went to look for the values that I had written down during the swap process, but was unsuccessful...

IIRC the chain weighed approx 3 lbs less and the sprockets combined were around 2.5 lbs less with the rear sprocket weighing only 14ozs total weight!

It may have only been in the 5lb range but it was substancial, and mostly in the chain as the 520 links are 6mm wide each as opposed to 9mm wide per link on the 530..

[kevin_stevens]

So, for those who care, a 1 1/4" ID by 1 7/8" OD machine bushing in 14 gauge will fit over the countershaft just about perfectly. It's just a hair big in ID, but you can snug the nut up and center it visually and it's just fine. Not like that whole assembly is very well balanced with those big nut tabs hanging out there, anyway.

No discernable difference in noise or vibration from the 20 miles or so I put on with the sprocket floating, but I feel better having everything nice and snug.

Tx all!

KeS