ICS L85 fps dropping

[Dan Robinson]

The boy's L85 has seemingly lost quite a bit of power,  sorting from memory 180fps on 0.28s last weekend. 

It is a few years old now,  and spent nearly a year hanging in the wall.   There is a chance the spring was under compression during this time,  but the boy insists it wasn't,  and recent skirmishes had better performances. 

So I'm wondering if we're dealing with a worn up rubber?   The reasoning being I chrono'd it this afternoon on 0.2s, and was getting around 340 (assuming my device is accurate).

Could this discrepancy mean his hop can no longer lift the heavier weights?

 

[Sewdhull]

piston o ring, nozzle or hop rubber would be my choices, all can be checked just dropping the gearbox out and checking pressures in  a ballparky way

 

[Dan Robinson]

Buggers have loctited one of the motor cradle screws in. ?

Anyway...cracked open the Boy's gearbox, and everything is tidy in there.  However,  @Sewdhull's thought on piston oring seems to be the culprit.  Very weak seal there.  Spring seems to be good, even though it was left under tension.

Does anyone know the best size oring for these? 

Bucking appears ok, although the nub seems to push through at an angle.

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Off to find a magic orimg box.

Cheers.

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[gavinkempsell]

Off to find a magic orimg box.

it'll be beside your batteries.

 

[Dan Robinson]

LOL.

Tried a couple but none were any better.  Seems to be averaging 250 now on 0.2g which isn't great.  Get the occasional blockage if there's too much hop too.  Frustrating as we're now back to orignal parts.

Will not get a chance to test long (arf)  range bop until gameday now which is a shame.  Even if the new bucking comes tomorrow.

 

[gavinkempsell]

Take a backup... or 2

 

[Dan Robinson]

Well...4 actually....my tappet plate doesn't look like it's arriving until Tuesday.... so the boy will be on one of the Specnas as a backup and I'll be in the DE or remaining Specna. 

Then again we still have is Bolt action and my SVU.......You know....just in case.

 

[gavinkempsell]

Och, well... remember to list the L85 as 'boneyard' & tag me

 

[Dan Robinson]

Changed the bucking and made things worse....BBs were getting stuck in the hop and the gun sounded generally awful.

I suppose that's because of Maple Leaf rubbers having bigger lips?

Put the oem back in and fps dropped even more...plus the usual issue of not always selecting single shot.   *sigh*.

 

[gavinkempsell]

I learned quite quickly to not meddle with my pews, don't mind bying boneyards for the wall but don't fancy making more.

 

[Dan Robinson]

I learned quite quickly to not meddle with my pews, don't mind bying boneyards for the wall but don't fancy making more.

Sadly this is in response to his pew suddenly dropping in performance with nothing changing.   Learned a lesson though....I'm only changing one thing at a time.

Next test is to swap the springs out between his and mine as there is nearly a year on his compared to mine, as its simple and non intrusive,  but I'm pretty certain it's something between nozzle and barrel. 

 

[Dan Robinson]

Well....don't I feel a bit of a dick?!?‍?

Not sure how I missed this on the last few strip downs....

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Teeth must have been disintegrating bit by bit.

Luckily had a few project/educational gearboxes lying around with metal teethed pistons.  Just chrono'd her and she's at 332fps on 0.2 bbs and zero hop.

Wonder how long my piston has to live now, plus why on earth did these get chewed up so completely?  The boy only ever uses 7.4v lipos and the box has never been opened before this probem started.... it didn't look like that when I first took it apart the other weekend (see the very first piccie).