Scooterotica

sean brady scooters wrote:

Ginch wrote:Hi Sean & Dan,

I've only recently seen this thread. The crank looks great and the open path from the inlet is impressive.
A german friend however says that it's pretty much impossible to statically balance this kind of crank. He's done a fair few and says he still has one similar to yours that didn't work due to lack of balance. I'd love to prove him wrong... can you please give your view on this?

If I was to buy one, what is the best base crank for you to start with?

seriously though ,i would be interested to know why he had probs ,and why he thinks its impossible ?
there are two ways basically to balance something ,you can either add weight like on a car wheel (lead weights ) hence increasing the overall weight or remove weight like the drillings on a flywheel ..hence achieving balance at a reduced weight ...and without giving too many trade secrets away i prefer the latter ...if metal is removed concentrically and uniformly balance is surely maintained
?...just like a 1500 gram flywheel can be just as balanced as a 3000 gram one
the trick is to obviously increase the flow rate (remove the obstructions ) whilst maintaining a balanced crank ..its not rocket science !

I don't know why he had such trouble... he sent me a comparison chart that measured static balance as percentages which I didn't entirely get.
Anyway I guess you can't really balance them as you go because you don't know what weight piston the buyer is going to put on there.

Are you able to fit a longer rod at the same time? And how would that, and the lack of a big chunk of crank web affect power - I mean as far as the larger crankcase volume is concerned? I run a 221 Malossi Sport (currently rotary valve), what difference would I expect with this crank?

Cartmel, thanks for the users perspective, very helpful! Just wondering why you started with a crank that had already been worked instead of the base crank?

Is the dyno you're talking about in the dyno section? Or in the Vespa dyno part? I can't see anything recent.

so what power are you getting now and what are you hoping to achieve ?....

sean brady scooters wrote:so what power are you getting now and what are you hoping to achieve ?....

I have no idea what power I'm getting at the moment to be honest. What I'm hoping to achieve is more power and probably more revs. At a recent track weekend on a 550 metre straight I was maxing out at 121km/h and 8600rpm according to the gps app and the sip speedo. That's with my crappy Scootrs pipe... looking at an RZ right hander as a next step. But for day-to-day riding I'm using a sip road.
The main reason I ask is that 1) the rotary valve is scored - I've repaired it with epoxy 2 or 3 times and while it doesn't appear to give any trouble eventually the epoxy is gone by the next time I open it up. And 2) I want to try/change to a PHBH or PWK carb. Touring type riding is mainly what I do.

Ginch wrote:

sean brady scooters wrote:so what power are you getting now and what are you hoping to achieve ?....

I have no idea what power I'm getting at the moment to be honest. What I'm hoping to achieve is more power and probably more revs. At a recent track weekend on a 550 metre straight I was maxing out at 121km/h and 8600rpm according to the gps app and the sip speedo. That's with my crappy Scootrs pipe... looking at an RZ right hander as a next step. But for day-to-day riding I'm using a sip road.
The main reason I ask is that 1) the rotary valve is scored - I've repaired it with epoxy 2 or 3 times and while it doesn't appear to give any trouble eventually the epoxy is gone by the next time I open it up. And 2) I want to try/change to a PHBH or PWK carb. Touring type riding is mainly what I do.

This crank is a bit extensive for what you are hoping to achieve. If I were you I'd simply go online to SIP and get a 60mm 'bell' shaped reed crank with 110mm rod, a Malossi reed valve and manifold kit, with a 30mm Dellorto PHBH. Port the inlet on the casing to match the new manifold and that's it, job done.

Simple, and effective.

Just to add to the clutch / flywheel weight thing, I checked mine, clutch weighs 1.3kg assembled, 4 plate carbon plates. Flywheel is 1.6kg - I don't know what the H4 weighs.

I also had a standard one lying about which had been lightened to 2.7kg

Mazzuchelli recommend 1.6 or less with their cranks - no explanation given as to why.

drunkmunkey6969 wrote:

Ginch wrote:

sean brady scooters wrote:so what power are you getting now and what are you hoping to achieve ?....

I have no idea what power I'm getting at the moment to be honest. What I'm hoping to achieve is more power and probably more revs. At a recent track weekend on a 550 metre straight I was maxing out at 121km/h and 8600rpm according to the gps app and the sip speedo. That's with my crappy Scootrs pipe... looking at an RZ right hander as a next step. But for day-to-day riding I'm using a sip road.
The main reason I ask is that 1) the rotary valve is scored - I've repaired it with epoxy 2 or 3 times and while it doesn't appear to give any trouble eventually the epoxy is gone by the next time I open it up. And 2) I want to try/change to a PHBH or PWK carb. Touring type riding is mainly what I do.

This crank is a bit extensive for what you are hoping to achieve. If I were you I'd simply go online to SIP and get a 60mm 'bell' shaped reed crank with 110mm rod, a Malossi reed valve and manifold kit, with a 30mm Dellorto PHBH. Port the inlet on the casing to match the new manifold and that's it, job done.

Simple, and effective.

Thanks for the advice.

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