TallPaulB

Active Member
If the compressor is good it should make around 175 psi quite quickly. So with a reasonable amount of pressure on the outlet it should blow past your thumb and give a burning sensation if you hold it on. This also checks the compressor exhaust valve. If it is puffing a good volume of air but it can be stopped reasonably easily then the exhaust valve is not sealing properly. If you fit a new piston seal always fit a new cylinder. Be aware of the maybe fitted Jap O'ring for the exhaust valve as stated in tech archive description.
 
I have found 2 different types of piston as well. If you take out the piston make sure you carefully tighten up the grub screw. Mine were very stiff and the first time I didn't tighten it up fully (although it felt like I did) and lots of noise but not really any air. I suspect the piston was spinning on the shaft. Anyway I retightened carefully and it's been brilliant ever since. Thanks to Wammers info and P38A site
 

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