PolarStar "Kythera" HPA Engine for Airsoft Rifles (Model: SA - A&K SR-25)

"I got this from a friend who was getting out of the sport and he had only run it through one game. I've installed about a dozen of these as well so I'm fairly familiar with the system and I am always impressed with the rugged reliability that the Kythera shows. I would recommend it to anyone who wants a fairly simplistic engine that is low maintenance and a fantastic results achiever.

*DONT FORGET TO LUBE YOUR ENGINE ABOUT EVERY 5 MONTHS OR 10,000RDS*

"I run it in a VFC MCX, had to cut the spring guide short with a pipe cutter to get it to fit. Was easy work (sit & spin lol). I threw in the 'Polarstar Gearbox Shim Set for Cylinder Conversion Kits (Size: 0.157")' shims and fit is perfect. You can empty an EPM pretty quick on semi the perks outweigh loss of auto for sure. It does exactly what a well tuned F2 does in semi when you follow P*s directions. Nice having something in airsoft that isn't constantly letting me down. Things a tank.

Use techT lube internally, the P* vids on youtube (watch em) explain even if you overdo it it'll just get cycled into the dump chamber. The vids explain how to set up the trigger pull, just follow the directions and use a tiny bit of blue loktite. It's really simple, all the people who say they don't work well didn't watch the vid. I haven't cleaned internals in a Millsim and dozens of games. I'd say plan to clean/lube every 4-6 months of heavy play, maybe yearly-more if you don't play much. No biggie.

Was told it's a temperamental system but I think they got greedy with the trigger pull. I run mine really short with near immediate reset just fine by following the directions in the vid. You have to go back the minimum amount of turns when they tell you, it costs you no pull & you won't have any problems with this unit at all. Like ever, things a tank. If you get greedy it won't work at all. If you run into issues start from scratch, once it's done right and loktit'd you'll never fk with it again.

All I have to do is throw my stuff in the truck and drive out to a game without waiting for batteries to charge if I forgot. Just came in clinch at a Milsim as a backup. Now I'm here replacing the AEG that went down with another Kythera. Things run like Gump once they get going.

Did Maxhop, Maple leaf autobot, 6.03 PDI & a G&P steel trigger. Right at field limits of 1.85j it's a laser. Feels like it want's to be a DMR, just runs better and better with more pressure.

"I bought the Sr25 version and put it in a cyma platinum sr25, it works just the same as the m4 version but be aware, the trigger will not reset properly unless you put all the spacers under the reset spring, the trigger will be harder to pull but it will work. overall, I feel bad using it because it's just unfair in some cases, the consistency and range/power increase is very VERY noticeable, I can hit 75 ~ 100-yard shots with this thing. if you hate money then I couldn't recommend any more.

"Bought a Kythera V3 and an Amped IGL for a CYMA AK-105. The only gearbox modification was a post that had to be dremmeled out. Tuning was quick and simple. Works great with no issues and is surprisingly efficient. One con which could be a pro to some is getting used to the heavier trigger. 5 Stars overall, highly recommend for any AK.

"Perfect for the SR-25 and the SCARAB

"Amazing trigger when combined with an amped igl it shoots perfect in my krytac. Note that to install in a krytac you will need to dremel out some metal in the gearbox shell to fit the grip line. Shoots absolute lasers my krytac pdw has been transformed into a sniper with the kythera. Amazing trigger pull which feels exactly like a real firearm. Worth every penny.

Pros:literally everything


Cons: semi only, needs dremeling to fit in a krytac

"Got this for my EMG Noveske. Had a donor V2 gearbox shell and it fit just fine. Running the UGS and have both CO2 Stock and 13c.i. Stock and have had a great time using it. Excellent trigger pull and reset. Fielded about 6 games now and have had no issues.

Make sure to use a little of the blue locktite or so sort of temp thread locker on the adjustment screws as they will back out due to vibration from shooting.

"Just got this for my A&K SR25k. Be wary some modification is required even though I have the exact model gun for it. Spring guide has to be cut if it holds the buffer tube for just about any V2 you drop this into. And on my A&K I found the right side of the gearbox has some grooves that the trigger mechanism will catch onto causing it to not fire at all. Adjusting the trigger itself and installing other than those things is very easy.

"I love my PolarStar Kythera it works so well I highly recommend it for new and old players.

"I just got this and immediately installed it in my Krytac AEG, and it works perfectly!!! The pop it gives is satisfying and now I don't need to deal with water damage. Since it is mechanical it is very easy ti install due to the fact that you literally don't need anything els besides a tube and a tank.

Awesome product!!