http://cgi.ebay.com/WACKER-JUMPING-JACK-TAMPER-GVR-151-Y_W0QQitemZ300090101063QQcategoryZ104215QQrdZ1QQcmdZViewItem\

"has good compression, you can tell by pulling the string.

i work on these, they require atleast 120psi to run and even then are hard to start. 140 is good. at 100psi they wont run but still feel like new. i wish i had an account so i could ask for a spec

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