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Post by novista on Apr 2, 2007 10:02:24 GMT
no, but that'll heat up then axle as well so i didnt think that would do any good? But that could allow you access to cut the axle, obviously your last port of call. I realised that wouldn't work, over the weekend, as the inner lip on the axle, wouldn't allow it to pass that way through. Good job to really! I'm going to shut up in future!
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Post by smallyshane on Apr 2, 2007 16:38:54 GMT
Sorry Hank.... It turns out I know even less about the inside of these things than I first thought!!! He never removed the drive shaft aparently... lots of heat though is his suggestion.. Juan, you say "more or less a bolt on" I have been reading up on these pistons and can't find much about them but from what i can gather sip recommend skimming 1mm off the barrel (not sure if top or bottom) to get the best from this piston due to the curved skirt or something.. If you could further translate this to english for me I would be gratefull... ww3.sip-scootershop.com/pages/index.php?ID=22545&EXPLODIM=px&_requested_page=%2Fpages%2Fdetails.phpSo, would doing this move the power further up the rev range? I am quite happy with the range that the scoot has at the mo and don't really want all my power up the top as I use it daily.. Or do I just go for the 1st oversize polini?! Just found a bit of spare cash that would cover whichever I decide on but now I have the dilemma of which to go for.... Cheers
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Post by Juan on Apr 5, 2007 18:10:41 GMT
Just noticed this.
Here’s the Mercedes of pistons! Practically all cylinders produced in Italy are equipped with ASSO pistons - with the same design for 25 years. It’s weakness lies in the material used for pistons and piston rings. Oliver from GRAND-SPORT has come up with a solution; high quality State of Technical Art conversion pistons in a limited edition. Picture this: racing sport pistons with 1mm piston rings sphero cast, chromed racing surface, cutouts on lower piston skirt (POLINI/MALOSSI/DR/ZIRRI) and closed piston skirt (original), including pistons pins. GRAND-SPORT pistons contain a higher Silicon ratio (>=18%) than standard pistons. For further information, view the piston and ring data file for download on the right. IMPORTANT: Increasingly higher proportions of silicon lower heat expansion rates while increasing wear and tear. Racing sport motors confronted with high thermal stress are all outfitted with high silicon ratio parts. Perfect pin spacing, optimal engine clearance make crankshaft and piston rods unnecessary. Extremely durable piston rings ensure a very wide outlet section, means higher performance 1.5-2 hp possible (see download).
Before installation, always control piston play, and if necessary, make adjustments! Unfortunately, there are a few manufacturing glitches and the usual wear and tear. Piston play should be about 7-8/100mm, measured under the piston pins, 90° towards the piston ring axle. Compression height is the distance between upper piston edge-middle piston pin. Compression height with GRAND SPORT conversion pistons for original cylinders = 29 mm. Compression height original cylinders 125cc = 36.5 mm. Compression height with GRAND SPORT conversion pistons for Polini/Dr/Malossi cylinders = 30.5 mm. Compression height Polini 130 cc = 36 mm/compression height Zirri 135 cc = 32.5/ compression height Malossi 136cc = 30.5 mm.
Pistons for original cylinders should always be outfitted with a window or cutout. Further performance potential for high end tuners here. If your MALOSSI cylinder intake is sufficiently widened, no need for a piston window, a cutout will be enough and your piston will stay stable.
SIP-TIP: for all GRAND SPORT conversion pistons the cylinder MUST be milled. The only exception is the GRAND SPORT conversion piston for MALOSSI cylinders, based on their same compression height. Generally, for optimal performance always adjust the compression/quench gap; which means the cylinder must be milled. Essential for all POLINI/MALOSSI and co. cylinders. Ideal for POLINI cylinders is the considerably more stable MALOSSI cylinder head. SIP-TIP: The POLINI has an unfortunate protrusion on its socket (overflow models will not open symmetrically to the max). Milling away the protrusion is the answer. Socket gaskets assure perfect valve timing adjustment and allows full utilization of the boost port. The housing should also be customized to the new overflow size.
Gibberish isn't it? ;DI'm not overly sure but I couldn't see that taking it from the top would make any differance so in theory that means lowering your exhaust port and making it torquier and slightly lower revving.I could well be wide of the mark here as I've never seen one in the flesh (metal?).My comment about bolt ons was about my 130,I'm fitting it to my ETS plant which'll be standard apart from a quick tidy up of the transfers.
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