JG Upgraded Piston and Piston Head Set
[05771 / JGM-86]
$14.00 $11.90
by C. MILLER verified buyer Date Added: Wednesday 26 August, 2009
Product Information:
I picked this up as an upgrade replacement for a Both Elephant HK33, as I was installing an ICS M120 spring. The overall construction seems to be good at first glance. Unfortunately, it fit too tight in the HK33's V2-hybrid gearbox and some slight modification was required.

When I first dry-fit the piston in the gearbox with everything except the anti-reversal latch and spring. With the gearbox tightened down, I attempted to move the bevel gear by hand. Once the sector gear started to move the piston back out of the cylinder, the gears stopped moving. There was an obvious binding at the piston. To double-check, I put my old piston back in and the gears moved easily.

I had to take a file to the piston's rails, as well as the body. I also used steel wool to polish the rails inside the gearbox. Fitting it all back together, it seems to move easily now.

The first tooth seems to come awfully close to the sector gear, so I took a file to it, to lower its height. I see no reason to remove the "wisdom teeth" (2nd & 3rd teeth), as the sector gear does mesh well with the first tooth.

I also found a problem with the piston head. A small notch on the plastic ring part of the head, between the o-ring and piston. It's a small notch, but I was worried it might possible affect the o-ring's ability to seal properly. I plugged up the end of the cylinder with my hand and tried pushing the piston in. It seemed like a good seal was being achieved, but I didn't want to take the chance. To fix the notch, I removed the o-ring, cleaned the area with rubbing alcohol, and applied a small dab of epoxy.

If I were to buy another piston, I would not purchase this one again.

By the way, the package shows that the brand is actually "Golden Eagle". No, not Golden Bow...Golden Eagle. Did a bit of googling, and it appears Golden Eagle is another one of those JG companies somehow.

Comes with a ball-bearing piston head.
Metal gears seem solid.
I believe this is polycarbonate ....it's was definitely not easy to file away the plastic.
Metal teeth are extremely hard steel. I had a tough time filing the first gear's height.

Poor fit in the gearbox causes the piston to bind. Required a lot of filing/sanding to get the piston to move freely in the gearbox.
The piston head has a flaw from the molding process, which could affect the air seal.

Rating: 3 of 5 Stars! [3 of 5 Stars!]
Back Write Review
JG Upgraded Piston and Piston Head Set
[05771 / JGM-86]

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