big bore installation
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big bore installation
Can any one clarify this will stock cylinder head bolt on big bore jug.not familiar with break in procedure on 2 stroke.
- Wheelman-111
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Re: big bore installation
Greetings:
In a word, no. The combustion chamber volume is that space that remains above the piston and below the head. Its size is carefully carved to achieve a survivable pressure when all the volume contained in the cylinder is crammed up into the attic. If you increase the size of the piston without enlarging the space under the head, well... there's just too many molecules trying to occupy that relatively smaller space. Compression ratio jumps to the moon, and a hot glowing ball of fire burns a hole in your piston crown to let them escape. You can add a head gasket or two to make that much more room, but the gasket should be the same bore size as your new cylinder.
In a word, no. The combustion chamber volume is that space that remains above the piston and below the head. Its size is carefully carved to achieve a survivable pressure when all the volume contained in the cylinder is crammed up into the attic. If you increase the size of the piston without enlarging the space under the head, well... there's just too many molecules trying to occupy that relatively smaller space. Compression ratio jumps to the moon, and a hot glowing ball of fire burns a hole in your piston crown to let them escape. You can add a head gasket or two to make that much more room, but the gasket should be the same bore size as your new cylinder.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
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Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
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- Elite
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Re: big bore installation
I fully agree with wheelman, however there may be a couple exceptions depending on what engine and bore kit. My polini bore on my variated AF05 calls to use the oem head.
Re: big bore installation
Thank you to those who responded.I used the same heads when building large displacement gas engines for autos. So since the dome is the same and head volume is the same, compression might be down a minor amount how ever displacement increase should be a win win. Just needed clarification on subject I will inspect gasket at jug and head when parts arrive. Not much on theory just don't want to do it twice/
- Wheelman-111
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Re: big bore installation
Greetings:
Compression will be higher, not lower. The polini for SE05 is an exception, but most kits come with a cylinder head. Measure compression before ignition. More than 150 on pump gas is risky.
Compression will be higher, not lower. The polini for SE05 is an exception, but most kits come with a cylinder head. Measure compression before ignition. More than 150 on pump gas is risky.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Re: big bore installation
Never use a base gasket with an o- ring gasket, this will lower compression.
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