Cylinder Kit - BGM or SIP GS

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ArmandTanzarian
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Mon Jan 28, 2013 10:06 am

Which of these two kits is the best basis for a HB style tune

The SIP Serie Pro

http://www.sip-scootershop.com/en/produ ... +_41470700


or the BGM

https://www.scooter-center.com/scoweb/p ... egory2=CAT
Meus Lambretta est non infractus. Is est quietus.

Spanish Fly
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Mon Jan 28, 2013 2:25 pm

For that amount of money you could have a cast iron Polini. Admittedly you would need a head to suit.

http://www.sip-scootershop.com/en/produ ... +_14000820

If you prefer a the standard configuration why not go for a used barrel, a rebore, and a better piston such as a Grand Sport?:

http://www.sip-scootershop.com/en/produ ... +_12090000

or what ever the piston is that HB supplies?

SF

gaz_powell
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Mon Jan 28, 2013 2:47 pm

if i was doing it again i would get a barrel and bore it to take a SIP GS piston 66.5/ 66.7/ 66.9 mm depending on the size of the barrel you get or a HB 68mm piston - both pistons use thinner 1.5mm rings (BGM uses the standard 2mm)

when i had mine done Harry used the brand new genuine piston i had at 66.5mm he had no issues with that but did try to get me to use one of his - but i didnt want to bore a brand new Autisa barrel from 66.5 to 68mm

I`m just about to start on a barrel (from the back of the garage) bored to 67.5mm to match a cheap thin ring piston i picked up - first impressions it appears to be decent quality - same weight a standard piaggio and good quality thin rings (might be a beedspeed one ?) - just blending and matching the ports, enlarge exhaust, increase windows in piston

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ArmandTanzarian
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Mon Jan 28, 2013 6:20 pm

I would use my own barrel and head but for reasons I can't be bothered to explain, they're no good (well - maybe the barrel is). Might go the second hand route if I can get a barrel and head for reasonable money.
Meus Lambretta est non infractus. Is est quietus.

johnny rotten
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Mon Jan 28, 2013 6:49 pm

Thought I would have to find a barrel piston and head for modification when I bought my HB 207 top end but harry supplied them as I didn't want to p/ex my standard 200 top end

turbovan
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Sat Feb 09, 2013 9:19 am

Harry's piston 68.0 and 68.5 uses wire rings ( Rik) from an old spec of cr250 honda, they are 1.2mm thick and the pistons were made to suit these rings, all the rest use cast rings.... which will not stand a wide exhaust, max around 44mm, approx 64%, wire rings allow wider approx 46mm, 67% for road longetivity.With cast rings the shape of the port has to be more oval and well chamfered, with wire rings the corner radiuss can be smaller approx 8 to 10mm. On a P2 cylinder you want width not height, Polini got it right! :-)

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