Scooterotica

hendy wrote: I would guess the clutch is less significant, in this respect though. I'd guess a clutch including all it steels, plates etc weighs about half what the flywheel does and that it's about the same diameter? If that's the case, Then it has about half the inertia the flywheel does. Still very important.......

All ok, right up until someone fits a HP4 flywheel because they read an advert about more horse power. Then the clutch is heavier and becomes the flywheel........but it explodes. So the same shop sells you an 'uprated clutch'. Lol.

how does the clutch know its heavier than the flywheel does it only explode when someone told it?

lol,the clutch knows when it starts to get beaten up trying to absorb the engine pulses,this is why you often find the tongues all chewed up and the bell housing grooved ..they explode sometimes but for often a different reason, which is the revs and centrifugal forces incurred by having a clutch on the end of a crankshaft !

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?

Are Vespa cranks known for being well balanced?


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no idea about your unbalanced german friend or his probs lol,but ours do work smoothly with good results as i,m sure others can tell you and verify

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?

The crank used on this engine started out as one of these; http://www.sip-scootershop.com/en/produ ... +_45034000 - which Sean then worked his magic on - further cutting/shaping/flowing, ect - till he achieved the desired result...

And I can honestly say that I've never experienced any running issues with this engine that would relate to an imbalanced crank - it's easily as 'smooth' as any other tuned px engine that I've ridden..... but then in all fairness, when I do ride this one I'm generally too pre-occupied trying to hold onto the bars & keep front wheel in contact with the tarmac to notice much else going on...

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 !

drunkmunkey6969 wrote:

Dyno graphs to follow......

has this been posted?

Can't check at the moment as I'm sitting in Tenerife drinking beer.....but I believe so yes. I think this went in Graham's 30+Bhp Vespa.....I think it's in the separate thread for that.

Why.....did you want a crank doing Eden?


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