If you take a look at the picture [http://shell.speakeasy.net/~bizwank/images/Photo0264.jpg|here], the large spring on the top holds a needle valve in place which plugs the portafilter; you can see the tip of it if you remove the filter basket. Once you start the brew cycle, pressure will build up in the brew head until this spring is overcome, at which point the coffee flows past the needle valve at high pressure, creating the crema. If your coffee is flowing very quickly after starting the brew cycle and you're not getting any crema, you may be missing this spring, your needle valve may be broken or the portafilter might not be correctly assembled. Individual parts for this portafilter are difficult to impossible to find, but replacement portafilters can be found at many online retailers; I would try [http://www.partsguru.com|Parts Guru] first.
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If you take a look at the pictures [http://www.ifixit.com/Guide/Repairing+Starbucks+Barista+Portafilter/4940/1|in this teardown], the large spring on the top holds a needle valve in place which plugs the portafilter; you can see the tip of it if you remove the filter basket. Once you start the brew cycle, pressure will build up in the brew head until this spring is overcome, at which point the coffee flows past the needle valve at high pressure, creating the crema. If your coffee is flowing very quickly after starting the brew cycle and you're not getting any crema, you may be missing this spring, your needle valve may be broken or the portafilter might not be correctly assembled. Individual parts for this portafilter are difficult to impossible to find, but replacement portafilters can be found at many online retailers; I would try [http://www.partsguru.com|Parts Guru] first.
If you take a look at the picture [http://shell.speakeasy.net/~bizwank/images/Photo0264.jpg|here], the large spring on the top holds a needle valve in place which plugs the portafilter; you can see the tip of it if you remove the filter basket. Once you start the brew cycle, pressure will build up in the brew head until this spring is overcome, at which point the coffee flows past the needle valve at high pressure, creating the crema. If your coffee is flowing very quickly after starting the brew cycle and you're not getting any crema, you may be missing this spring, your needle valve may be broken or the portafilter might not be correctly assembled. Individual parts for this portafilter are not available from the manufacturer, but you can buy a replacement portafilter from [http://www.seattlecoffeegear.com/Saeco-Pressurized-Portafilter-53mm-p/scg226552008.htm|Seattle Coffee Gear].
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If you take a look at the picture [http://shell.speakeasy.net/~bizwank/images/Photo0264.jpg|here], the large spring on the top holds a needle valve in place which plugs the portafilter; you can see the tip of it if you remove the filter basket. Once you start the brew cycle, pressure will build up in the brew head until this spring is overcome, at which point the coffee flows past the needle valve at high pressure, creating the crema. If your coffee is flowing very quickly after starting the brew cycle and you're not getting any crema, you may be missing this spring, your needle valve may be broken or the portafilter might not be correctly assembled. Individual parts for this portafilter are difficult to impossible to find, but replacement portafilters can be found at many online retailers; I would try [http://www.partsguru.com|Parts Guru] first.
If you take a look at the picture [http://shell.speakeasy.net/~bizwank/images/Photo0264.jpg|here], the large spring on the top holds a needle valve in place which plugs the portafilter; you can see the tip of it if you remove the filter basket. Once you start the brew cycle, pressure will build up in the brew head until this spring is overcome, at which point the coffee flows past the needle valve at high pressure, creating the crema. If your coffee is flowing very quickly after starting the brew cycle and you're not getting any crema, you may be missing this spring, your needle valve may be broken or the portafilter might not be correctly assembled. Individual parts for this portafilter are not available from the manufacturer, but you can buy a replacement portafilter from [http://www.seattlecoffeegear.com/Saeco-Pressurized-Portafilter-53mm-p/scg226552008.htm|Seattle Coffee Gear].