Gen8 with basic upgrades has poor performance, asked retailers and friends no one can diagnose

So a few weeks ago i decided it was time to get back into the game and after doing some research was glad to see Gen 8’s were still super viable, so rather then trying to learn something new i thought the best place would be to start with a gen8 and work my way up.

In all honesty i didnt really test the blaster, so figuring out if its manufacture fault or user error is almost impossible.

I run 2-3 mags through it after purchase then tore it down and installed an oversized O-ring, and 1.3 spring, and chucked a fully charged 11.1v into it. after running a few mags through it I noticed a grinding sound after firing and realised the anti reverse latch had come loose, I fixed that up and the next day went to a local game, i played for a solid 3-4 hours and felt like it was under-performing however wasnt using a hop up so assumed that was the issue. Bought a hop up and was getting fairly tight spread at 15 m and was somewhat happy with its performance.
A week later i took it into a local retailer and asked them to chrono it for me, only to find out it was only doing about 180-190, i asked the guy what he thought and was told to put in an alloy barrel and seal it as much as a could, we also replaced the return spring as the one i was using already had some rust and was coated in smashed gels, we tested it again and it was at about 240-250, which is what a stock V8 runs at, which still didnt make sense because it had a 1.3 and good seal in the cylinder. It was at this point when comparing it to the stores demo V8 that i noticed it still had a grinding noise, mind you using nylon gears, and the demo one was sounding much more slapier and cleaner with a clean thud at each trigger pull, where as mine had this winding down noise after each shot. I left the store confused and went and bought some silicon lube so i could pull it down when i got home and just check everything like gears and what not. After not finding any issues as in no wear on gears or stripping or any noticeable snags in the gear movement i re-greased and put back together, now is probably a good time to mention i accidentally run the gearbox without the spring in it by accident just as a slip of the mind when rebuilding, it was only 1 or 2 trigger pulls and didn’t hear any noticeable change in the way it operated when put back together. After doing some more testing and getting some new cosmetic pieces i took it to a friends house to get some stuff custom fitted and see if he could figure out the issue. when we chronoed it, it had reverted all the way back down to its original 180-190 fps, he agreed that the problem has to be something with the gears as there the only thing that could really make a grinding sound and he told me he would swap them out for metal ones to see if that fixed the issue.

After a week he got back to me and told me he couldnt fit the gears he had into the gear box for some reason, and that he put it back together making sure everything was done right, but the blasters still only at about 200 fps… im lost, i think its worn down gears due to misuse, or an airleak somewhere, but most joints have been epoxied now and its still playing up, i was thinking of going to get some new metal gears from the retailers so there fit for the gen 8 nylon box, but im still not even sure if this will fix the problem so im here for anyone’s opinion, and guidance on what to try next.
I read alot today about the nozzle coming loose or just sealing that with epoxy which i have not tried yet.
and does anyone know why metal gears wouldnt grab the piston in a gen 8 nylon box but would in a Gen 8 ABS box? or is my mate just having me on and was probably too lazy to try it??

Thanks for your time

Welcome to the group! :+1:

So did your tech have problems fitting nylon gears or was he installing metal?

Might be the bearing bushes in the gearbox case haven’t been installed properly… had that problem with my Gen 8. Installed all metal upgrades but did have to take a little off those bearing lugs to get enough clearance to shim for correct end float. Got a good result.

If you have everything apart, easy way to check is try each gear in the case on its own. With the three screws around the gears back in, check for freeplay and clearance when you spin it. If you find a tight one, look at the bearing bushes.

Yeah he was trying to install metal gears into a nylon box, but when he reassembled he just put my original nylon gears back in, but this could have something todo with it because the bearings he was using in his box wouldnt fit inside my box so it could certainly have something todo with it, but the grinding noise and performance issues are happening with the nylon gears that came stock with it, should i still check this with my nylon gears? either way i may end up buying metal gears tomorrow and this will be the first thing i check, did you just shave them down with a dremel?

Could be as simple as the motor not put back properly? O.O??

yeah in all honesty i was thinking this, because we did replace pinion gear at the same time, and he was just like just push it on as far as it goes and grub screw it in and it should be fine. In terms of the motor being properly set into the gearbox i can assure you it was i tried building the box 4 times with him, and then left it with him to see if he could figure it out, and everytime i did it, it was secured exactly the same as how it was when we opened it besides the pinion gear. It sounded like the gears were catching fine there was no high pitch whine or scrapping noise from the pinion, it was only the piston that wasnt getting grabbed, mind you this was the same piston he was running in his box that we also swapped out for metal teeth.

I did have some problems setting the motor pinion to the crown gear… crown spun fine in the box on it’s own, but was tight with the motor in… little nylon off the bush lug and it freed up.

Low Guido and Galapagos J both have handy vids on this. Might help you out.

Oh, and find a new tech… pinion gears have to be precisely set, not slapped on as far as they can go. :+1:


yeah fair call man, im fairly sure i have seen both of these videos and thought the pinion needed to be set, but as i say last box i opened was like a Gen5 or something and the scenes changed a fair bit since then, no need to find a new tech as im keen to learn all this myself, ill go out tomorrow and get metal gears, a shim pack, and maybe even some bushings/bearings and sit down and watch both the videos again and do it all myself. Fairly sure my mates just fallen out of it as well and forgets the details. So just for clarity your saying having a bad AOE on pinion could make the whole gear set go of balance or something and not grab piston properly? and grinding down some of the bushing on the crown gear might free it up? once again if i run into issues after rebuilding tomorrow, these are the things ill try

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With the motor in place and the gearbox split, couldn’t drop the crownwheel gear in to check pinion location & mesh, it bottomed out on the gear before it properly located in the bush. Confused?

Bottom line, the metal crown gear was dimensionally different to the nylon, significantly. The crown gear would freespin in the box fine, but be pushed up to one side of the box with the motor in. And no amount of pinion adjustment would correct it.

Can anyone back up that gen 8s do a consistant 250fps out of the box? Or more that thats what they can reach?
What type of 1.3 spring was it , as theyre not really a good system for comparison.
Chuck an m90/m85 youcll be up around 300.

I was expecting around 250 when i got my chrono as i thought stock was 250 lol.
My 2 stock nylon m4 gen8s with airseal fixed , greased and oiled, green oring and 1.2/1.25 spring gets me a pretty consistant average of 230 on both. The odd shot does go up to 250 but the point on these of mine is to keep under 250.

I should mention im talking about the 2019/2020 re-release M4A1, and only reason i said that was because i watched the guy pull one out of a box set it up and chrono that while testing my blaster and it did 240-250, but i understand that could have been a fluke build from factory or something, thats just what i saw.

Oh its pretty common to hear j8 j9 j10 do 250 out of the box. Bit weird with black oring , shit air seals and a 1.1mm spring yeah?
I didnt have a chrono at the time of purchase to check mine , which is why i was surprised with 230 .

I wonder what a 250 out of the box does after the recommended 2000 gels being put through it to wear in the spring.

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yeah no i completely agree its china black magic, who knows how they managed that haha

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My stock Gen 8 M4A1 was hitting pretty consistent 230s on a chrono before upgrades.

Consistent 290s with all the upgrades. :+1:

Mind listing what you did pls?

Im getting 300avg in a gen 9 from just oring seals and m90. Best $15 upgrade ever.

Good value upgrade on the Gen 9! :+1:

Gen 8 came with a nylon gearbox and got : 18:1 SHS metal gears, upgraded cylinder, double o ring alloy cylinder head, nylon piston / metal rack, alloy piston head, alloy double o ring nozzle, green o ring, 35cm alloy barrel, 1.3 spring, heavy tappet spring, 11.1v 3S lipo. Put it to the chrono yesterday using green ATs, nothing below 285ps, average 290 and up.

Not bad for an old Gen 8

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