Benjamin hand pump rebuild kit ?

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Back when I was hand pumping I used to get all my re-build kits from sunopticsusa.com for the Benjamin Pump. I don't know if they are still selling the o-ring kits, but I did notice that they are still selling the Dissicant kits for the Benjamin Pump. Sun Optics are, or were, the original manufacturers of the Benjamin Pump. Give them a call Mon-Fri (Texas Time) at 817-783-6001 and ask if they are still selling the re-build kits for the pump. I was getting mine there about 2 years ago … they are not very expensive.

You are correct, the O-rings WILL fail on that pump … I re-built mine about 20 times and it is usually the small o-ring at the base of the plunger … unfortunately you have to pull the whole thing apart to get to it. After the first few times you should be able to take it apart and get it back together in 30 to 45 minutes … not a big problem just agrivating.
 
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Agreed on reaching out to Sun Optics. I can't seem to locate the repair manual on their site any more but here's a copy I archived:

https://www.dropbox.com/s/sfkzj53hw8rnz23/Sun%20Optics%20repair%20manual.pdf?dl=0

Failing that, here's a diagram with the sizes. All of them are standard AS568 sizes and easy to obtain. Definitely use a 90 durometer for the high pressure O-ring (#8) on the end of the inner piston, else it will quickly extrude and fail. Everywhere else, 70 durometer will do fine.


 
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The first pump was replaced under warranty, used less than 60 days, the replacement is less than six months old for a total of 2500 shots. I'm ordering the kit with 3x o-rings for three rebuilds. I'm also going to order the Hatsan Spark compressor and keep the hand pump for backup. I read a review of the Spark on GTA and the owner had seven hours run time.

https://smile.amazon.com/gp/product/B07TBNZPYZ
 
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