race,full circle

[jake]

what is the difference between a race crank and a full circle crank

[ozzy]

they're for different kinds of engine. you can see the physical differences.

the full circle is for a reed valve engine; it fills up the crankcase with crank to improve crankcase compression.

the non full circle race crank is for use with engines still using rotary valve inlet. It would probably differ from a standard crank by having a polished conrod, the surfaces around the crank web will probably be flowed to aid gas flow, and the part of the crank that seals against the crankcase will probably be modified to extended the inlet timing.

[jake]

thanks mate,what about the worb5 race crank on sip,no 46090000 says for reed is this full circle?

[ozzy]

yeah thats a special lip, basically its more gas flowing on a race crank for when you don't need rotary valve anymore. this is for reed motors that breath through an opened up 'standard' inlet, using somthing like the polini reed kit, not motors like m1l/falc/parma where the reed comes in the side of the barrel. the first obstruction the gases really meet is the crank, and as with reed you don't need the sealing of the rotary valve anymore, its machined round and smooth, compare the pics of this and the race crank,

[jake]

thanks very much mate,so for parma i def need full circle,any ideas on ign,hp4 or variotronic

[ozzy]

yeah definitely full circle with the parma. some people winge about hp4's as the magnets aren't that strong and the lights arn't that bright.. i've used one and i liked it, its sooo light, 1000g, that the bike feels really revy. lighter = less torque used accelerateing the flywhel and more torque used accelerating you. i'm not sure how light the vespatronic flywheel is, 1600g springs to mind, some people have mentioned that they have similar lighting issues.. i just noticed the parma variable ignition comes with a choice of 1000g or 1600g flywheels?? in theory variable igniton is a very good thing, it allows more advance at low RPM to burn better when the scavenging is less efficient/optimal, but safer/less advance at higher revs when the exhaust and everything is in harmony and your motors scavenging more effieciently... so it should allow more low end power but safety from detonation in the high revs... as for how effective the new vespa kits are i've to see comparison dynos? they seem to be used by all the italian sprint guru's so they can't be that bad.. ramble ramble... ;D

[darkryder]

I have the HP4 and its very light and revy but the're issues with lighting, and in my case (PK50XL) ignition cuttouts at mid-high revs with the lights on... long story. As a suggestion lightten your original flywheel on a lathe at a machine shop, this is about half the price of the HP4 and mutch better quality, maybe you wont finish up with a 1000g flywheel but 1200g or so.

This is just from personal experience, results may vary ;D ;D

[ozzy]

i've got a lightened pk fly, beedspeed did it (cheap!) they have taken loads of meat off it but it only down to about 1600g, bit of a disapointment, but as aston says, at least i've still got proper power for my lights.
also, something that never get mentioned in discussions about flywheels; the distribution of weight is important, loosing weight out at the edges of the flywheel is worth more gains than loosing wieght at the center... hold onto the axle of somthing the size of a large skateboard wheel that weighs 1kg and rotate it.. it'll be easier to accelerate than trying to do the same to say a mountain bike wheel of the same weight.. i'm not sure exactly how this relates to the scooter flywheels on the market, but i reckon the hp4 with plastic fins has less weight around the circumference than a lightened pk.... another alternative would be to machine the fins completely off a pk and stick an hp4 plastic fan on it, best of both worlds??? or just splash out and get the parma 1kg

[jake]

thanks lads,looks like the parma then.

[ozzy]

before you burn your cash wait until others have chipped in i'd feel bad if it was crap ;D i can't remember if adspeed bought the parma ignition, or the vespatronic?? and like i said, you see the orange flywheel of the vespatronic on loads of the very very fast italian sprinters... so if its good enough for them

[jonnysnatchsniffer]

im not sure its the magnets strength that comes into play much or you would have trouble starting from warm, its the thickness of the windings on the stator and how many times thier wound round the stator, rewind with fatter wire and you get more power in wattage for your lights, but it will come at a cost of hp as when you put on your lights there will be a strain on the flywheel/stator because of load, for example a motor running at 20 amps at full cuurent load will pull 20 amps but if you lock the motor up it could pull up to 100 amps now its the same with a scooter, as motors and alternators are pretty much the same, ive put 55watt bulbs in a scoot before and it struggled to keep ticking over, also not good for yr main bearings, but enough shite from me just keep it light and fuck it if ya cant see much at night, sellotape a pushbike light on the headset ;D


what a twat this is the wrong thread i was supposed to post this in the flywheel one doh