HP4 Flywheel

Hi All, I am considering an hp4 flywheel for my malossi kitted 210 and wondered if anyone had fitted one?
If so does it really make a big difference to acceleration/top speed?
I have heard they can cause clutch problems and more vibration did anyone find this?

  Thanks Mark.;D

do you still get the clutch problems with a cosa clutch that have been stated ie exploding

No (At least I did not put any clutch problems down to the flywheel…what would they be?)
No (but louder) (Norrie Kerr…guy who wrote Vespa tuning book reckons lighter flywheels are better for bearings and general wear&tear on the crank)
The only downside: The magnets are weaker than standard though…I’m running all AC and my lights ar quite a lot dimmer…not much better than a 6volt system in fact
Some say they are not as good at cooling as the fins are smaller.

Try a PK125 flywheel modified for a Px200. No lighting problems, lighter than std but heavier than HP4. Whats more its Piaggio.
Bought one from SIP, no problems with it.

quick question, when you band your clutchs do you worry about balancing them or do you bodge them and hope their balanced??? ozzy

Thanks for taking the time to reply.
The HP4 certainly sounds impressive performance wise but I am not sure if I am willing to take the clutch hassles it may bring as I use the scooter for rallies and so need to rely on it.
With the scorpion pipe the power dosent kick in 4th[T5] till 70+mph and I thought the HP4 may help it to bridge the 3rd to 4th gap, may just try another route.

 Thanks again Mark.[:look:]


To my thinking you should consider it. I invested in mine to overcome the 3rd/4th gap problem,and it has helped considerably.

You’re running a (presumably matched) 210 and expansion pipe and really should get a reinforced clutch anyhow for rally work as much as any other use (that = uprated springs and a welded ring on the basket)…the basket expands at high rpm and as you will be revving the tits off it in 3rd to get lift-off in 4th you’ll need it as much as ever. That will cover the ‚revving higher‘ potential problem.
As for more strain on the clutch plates…I don’t see that myself…less dead weight on the end of the crank means an easier life for the clutch when changing (ie easier and quicker match to engine speed). More rpm means more power spread through the clutch…sure but it is progressive so doe not cause excessive wear. If you end up generating so much power that you have clutch slip well that is the least of your worries, most people spend a good few hundred (if not thousand) quid getting to that stage: Just buy a cosa clutch (4 plate) and you are sorted .
But do get stronger sprngs (Malossi are good) and a band welded on the basket then you can ride without the worry of your clutch exploding.

if you use a good welder he will put roughly the same size tig welds all round and with the band being the same width all round any slight variation in weight around the basket is so negligible it aint worth a worry.big blobby mig welds however are a different thing and will need grinding down so they dont foul the casings the tolerance is that close

i run a 210 px with standard setup(carb/autolube etc) which sits nicely at 65 at 5500rpm and it revs out at 8000rpm.fitted a hp4 flywheel it wheelies in first three gears and now revs out at 9000rpm,using a 138 main jet.it f***in rocks hp4’s are the dogs nuts,YOU MUST USE REINFORCED CLUTCH PLATES,PRINGS AND BASKET or the clutch will find every inch of your gearbox to hide in.bear in mind the weight of the flywheel eases the acc/deceloration forces of the engine,with the hp4 its the clutch that does this so it can shear the tab washer and snap yer crank off so treat them with respect