STAR L85 Poor FPS

[Rev Golightly]

OK I have an STAR L85, been using it for quite a while and happy with it, however chronoed it at TA4 and was gutted to find it was firing at 220fps. I had not noticed any distance problems and it performed weel at TA4 however 220 is ######, when last time i chronoed it it was dead on 345. I put the original "cut down" spring back in that gave 366 and I got 240.

 

I cannot understand how this has dropped off but it would seem to be leaking air around the front of the box/hop.

 

There seemed to be some scratches in the cylinder and some wear on the hop casing/ nozzle.

 

Mods up untill the low fps were

 

Marui EG1000

Marui gears

Solid bearings

Marui piston

Marui hop/ bucking

 

Mods once low fps discovered

 

Systema cylinder

taped hop rubber (ptfe tape)

Barrel cleaned

 

Result small increase in fps but nothing spectacular.

 

Lates addition will be new STAR nozzle, Prometheus vented/bearing piston head, new marui hop/ bucking. Gearbox is perfect mechanically all is lubed up. with marui grease (not over lubed either).

 

Before I put it back together and re-chrono, anyone else seen this and more to the point, anyone resolved the problem?

 

Its a great AEG build wise, shame about the fps.

 

Any ideas would be really appreciated

[Noxman]

Chances are this is something different but I had an fps problem with my STAR g36k.

It dropped from like 300 to around 260 then dropped off the edge and started shooting at like 120fps.

Got it opened up and it apparently had a cracked cylinder head. Since had a hurricane tune up put in there and now it works fine.

This could be something different though...

[RazorOne]

Chances are this is something different but I had an fps problem with my STAR g36k.

It dropped from like 300 to around 260 then dropped off the edge and started shooting at like 120fps.

Got it opened up and it apparently had a cracked cylinder head. Since had a hurricane tune up put in there and now it works fine.

This could be something different though...

<{POST_SNAPBACK}>

Here is something simple try cleaning the barrel and lightly swabbing it with siliconm then wiping most out with a dry barrel cleaning cloth. That can affect fps a lot...

 

RazorOne

[Perch]

Maybe it's the pistonheads O-ring.

The STAR-Pistomhead isn't the best one.

[Rev Golightly]

Looks like the nozzle may be leaking, so..........new STAR air-seal nozzle, another, new, Marui hop/bucking and a Proetheus vented, bearing piston head. See what happens next.......so I did all that, taped the hop onto the inner barrel, taped the hop into the gearbox, lightly grease the nozzle...M100 spring...275 fps

 

Remember this is not a V2/3 type gearbox, however the box is sweet, but I cannot for the life of me find a leak else where

 

BOLX

[Robin]

I'm with Perch. It sounds to me like you're getting bad compression in the cylinder.

 

To test this take the cylinder set from the gearbox. Remove the spring and piston from the cylinder and the nozzle from the cylinder head. Point the cylinder head downwards and drop the piston down the cylinder. It should slide down in a second or two. If it drops very quickly then it looks like bad compression is your problem.

 

Now repeat but with your finger blocking the cylinder head. The piston should move very slowly or not move at all with good cylinder compression.

 

If you're getting bad compression you will need to replace your piston head o-ring. Cheap and easy.

[Rev Golightly]

I'm with Perch. It sounds to me like you're getting bad compression in the cylinder.

 

To test this take the cylinder set from the gearbox. Remove the spring and piston from the cylinder and the nozzle from the cylinder head. Point the cylinder head downwards and drop the piston down the cylinder. It should slide down in a second or two. If it drops very quickly then it looks like bad compression is your problem.

 

Now repeat but with your finger blocking the cylinder head. The piston should move very slowly or not move at all with good cylinder compression.

 

If you're getting bad compression you will need to replace your piston head o-ring. Cheap and easy.

<{POST_SNAPBACK}>

 

Box has a new Systema cylinder and a prometheus vented head and it does exacltly what you said, i.e. it doesnt just drop down, there is some air resistance, much more when the cylinger head is blocked ???????

 

Getting beyond a joke now

[noodels]

Venterlaed piston head O rings tend to shrink ( my systema one did, lost almost all compretion ), try streching it by hand & testing it again as explained above.

I did this & it went from 0 to full compretion!.

[Rev Golightly]

Venterlaed piston head O rings tend to shrink ( my systema one did, lost almost all compretion ), try streching it by hand & testing it again as explained above.

I did this & it went from 0 to full compretion!.

<{POST_SNAPBACK}>

Its a brand new piston head, but hey it's worth a shot

 

Thanks

[serioussniper]

my m249 has the same issue. It was shooting 180ish when I recieved it 2nd hand

 

Compression was about 50%, I put a new o-ring in the piston head and compression is now about 95%.

Fps is 240

 

Strip the hop, ptfe the hop and replace the bucking 280 ish.

 

After that i've not tried anything, however the issue seems to be with the hop and hop alignment.

 

Hope this helps!

[Rev Golightly]

my m249 has the same issue. It was shooting 180ish when I recieved it 2nd hand

 

Compression was about 50%, I put a new o-ring in the piston head and compression is now about 95%.

Fps is 240

 

Strip the hop, ptfe the hop and replace the bucking 280 ish.

 

After that i've not tried anything, however the issue seems to be with the hop and hop alignment.

 

Hope this helps!

<{POST_SNAPBACK}>

 

Thanks for the info mate , will try all options

[Rev Golightly]

I cant believe I am the only poor sod who has had this problem!! Come on people, I am out of ideas

[cjfield1129]

I experienced poor airseal in my Star L85 as well when I upgraded to a bearing piston head, new bucking, and tightbore barrel. I firmly believe the problem to be with the nozzle and hopup combination. It came with so much goop that it used that to maintain the compression. My best results so far have come by getting excellent cylinder compression (a must) and then using a thicker Guarder clear bucking. Keep working with the cylinder compression issues until the piston can't be pushed forward while doing the "finger test". Hope this helps.

[Rev Golightly]

I experienced poor airseal in my Star L85 as well when I upgraded to a bearing piston head, new bucking, and tightbore barrel. I firmly believe the problem to be with the nozzle and hopup combination. It came with so much goop that it used that to maintain the compression. My best results so far have come by getting excellent cylinder compression (a must) and then using a thicker Guarder clear bucking. Keep working with the cylinder compression issues until the piston can't be pushed forward while doing the "finger test". Hope this helps.

<{POST_SNAPBACK}>

 

Thanks mate, what bearing piston head did you use? Did you only change the hop bucking or the hop rubber as well?

 

Thanks

 

Rich

[cjfield1129]

I used a prometheus bearing one. I changed the hop up bucking. Bucking and "rubber" are synonimous terms. But yes, I changed that to a guarder clear bucking.

[Rev Golightly]

I used a prometheus bearing one. I changed the hop up bucking. Bucking and "rubber" are synonimous terms. But yes, I changed that to a guarder clear bucking.

<{POST_SNAPBACK}>

 

Just to clarify you changed the bit that looks like a piece cut of of a bic pen inner or the whole rubber that fits over the barrel and the tube bit, as I cannot see what changing the piece that bears down on the rubber from the hop adjuster to provide the hop effect would do???

 

But hey if I am wrong great if it fixes this mess .....result

 

Thanks for any update CJ

 

Rich

[cjfield1129]

I changed both (the bit and the bucking). The effect would be with consistency. I like using the bic pen bit actually. The plastic material does not flatten over time like the rubber ones do (esp the ones made by Star and CA). It does not have any effect on FPS though..just consistent hop effect.

 

Any progress with the FPS issue?

[Rev Golightly]

I changed both (the bit and the bucking). The effect would be with consistency. I like using the bic pen bit actually. The plastic material does not flatten over time like the rubber ones do (esp the ones made by Star and CA). It does not have any effect on FPS though..just consistent hop effect.

 

Any progress with the FPS issue?

<{POST_SNAPBACK}>

 

Hi mate, gonna get a new bucking/ rubber from Guarder and go for the bic option as well, let you know

[lorant]

so did you ever figure out what the problem was?

 

I just bought a used stock one and it seems to have really low fps. Im going to take it apart tonight and check the cylinder.

[lorant]

Works like a charm now. the cylinder had no compression. replaced o-ring with a larger one from a hardware store and its got full compression now.

[Stealthbomber]

Glad to hear you got it working.

Also nice when people actually bother to return to a thread to tell us what the problem was and how they fixed it.

[chownsy]

Glad to hear you got it working.

Also nice when people actually bother to return to a thread to tell us what the problem was and how they fixed it.

 

 

i dont think that was the origional chappie, this was someone else with the same/simular problem but reading it mostly pointed toward the problem of a bad o-ring.

[PUMPUK]

Well, first off i'd recommend EVERY airsofter bought their own chrono (helpfull when upgrading/testing)

Secondly, ouch for you 220FPS in a L85! Sorry to hear that, but i've got no real advice so i'm just going to be typing abit for no real reason or point, so pretty much its pointless posting this.. Yet i'm going to!

[Stealthbomber]

i dont think that was the origional chappie, this was someone else with the same/simular problem but reading it mostly pointed toward the problem of a bad o-ring.

Yes. Any other blinding insights you'd like to share with us?