Our latest spec reed-valve crankshaft - (Malossi 221cc)

[shamrockexpress]

Horses for courses............................lesson learnt
Good luck.

[sean brady scooters]

Everybody is making bigger cranks and bigger casings to house the bigger cranks like Jap style cranks with fat webs with more surface area on the pinsto stop twisting..........................
So good luck Dan if you can make them smaller and work all the same CERTAINLY REVOLUTIONARY.

if you take another carefull look at the pictures you will notice that the crank pin has been welded up also

[sean brady scooters]

Out of interest.. what's the advantage to a lighter crank?

tbh ,is not the actual weight difference on these that counts ,its the inceased flow over the intake side web area that makes the difference .
I only mentioned the weight difference to dan in order to show how much metal has been removed by comparing the weight of this one to a std crank .all modified crankshafts are gonna be lighter than a std one ,wether for reed or rotary ..but as you prob know weight removed from an area so close to the crank axis has little effect as compared to weight removed from further out as on flywheels
the bell shaped cranks are probably of a similar weight to this one if not lighter ,but the bell webs still obstruct the 360 intake at certain crank angles .
i should perhaps have said that these slightly lighter cranks give the benefit of not needing to purchase special light flywheels ,as a std leccy start flywheel is just about perfect .

[Micky Tapp]

Dan, apart from being easier to carry in your jacket pockets while doing the big shop around Asda, I can see less weight for the engine to waste spinning the crank= more horses left to push the scoot through the fog, but what about low revs? What happens to tick over, do you have to rev its nuts off while at the lights outside the local plod shop, hence attracting the attention of our old mates the anti fun monitors?
How did you develop such a crank, was it difficult to estimate how far to go when taking mass off the crank? It's not like you had a skip full of them, so when you f'ed one up you could just get another and grind slightly less off next time.

[sean brady scooters]

As mentioned earlier ,these cranks are roughly the same weight as the "bell cranks " now available which work well and do NOT affect tick over speeds at all or require mega revs to set off as you ask .
Our cranks are made this way to improve flow ,hence improving overall efficiency ..if anything they actually do improve torque and low down grunt .
Again ,do not fixate just on the weight of a particular crankshaft as its the whole weight of the crank train assembly that needs to be taken into consideration ..crank/clutch and especially the flywheel .
For this reason ,I would only recomend the use of a standard electric start flwheel with these ,usually with only the ring gear removed if E/s is not required .
flywheels that are too light do affect the smooth running at low revs ,and can cause other problems ...it was a common thing a while ago to use the hp4 light flywheel but because these were too light at approx 1200 grams they put extra stress on the clutches that were trying to absorb the engine pulses so destroying the clutch plate tongues and the bell slots ..cush drives took a good beating also .
As for how these have been developed ,well simply "slowly but surely" and over a number of years by doing a little more each time finding only improvements and no detriments ..the more I improved the flow over the restrictive intake web the better the engines responded .

[Micky Tapp]

Thanks for the explanation Sean

[ducksta]

Do you have a ball park figure to mod a standard crank to this spec

[OzOAP]

One thing I do, maybe waste of time, I'm sure I'll be told, is to weigh the crank web and clutch assembly, then weight the other web with flywheel, then lighten the flyweel to achieve same weight.
The T5 flywheel on my TS is at 1645g doing this calculation.

[sean brady scooters]

One thing I do, maybe waste of time, I'm sure I'll be told, is to weigh the crank web and clutch assembly, then weight the other web with flywheel, then lighten the flyweel to achieve same weight.
The T5 flywheel on my TS is at 1645g doing this calculation.

ok thats interesting as I have never yet known anyone to do that ,is there a particular reason why you do it ..balance the weight of flywheel side of crank to clutch side of crank i mean ?
only asking because this would not be possible on say a small frame vespa or lambretta when all you have mounted is a drive sprocket instead of a heavy clutch !,unless you would be happy with a 500 gramm flywheel lol

your flywheel weight/mass sounds about ideal btw however you arrived at it and obviously suits you and your riding style ,but I choose flywheel weights in a different way tbh ..mostly based on experience considering the state of tune and on the intended use by the customer .lighter riders who ride only one up and fast keeping the motor on the boil can get away with lighter flywheels whilst those that prefer a touring style often twos up with luggage etc require a heavier flywheel to ensure smooth low speed operation and cruiseability at lower revs .
but here are two things i know for sure ...the old type PE/PX flywheels are too heavy at 3 kilo,s and that on a PX/PE the hp4 type @ 1.2 kilo,s too light in most cases

[sean brady scooters]

Do you have a ball park figure to mod a standard crank to this spec

yes mate ,approx £140ish ,..P200 cranks are cheaper to do than t5 ones though cos of the thinner webs /more metal to remove on the t5 cranks ..
extras are tig welding to the pin if required and return Pand P costs .