HW90 problem, Gas ram leaking past Orings.

[Commando]

So this is my first post on this forum,

I have a HW90k .177, bought new by me just over a year ago, when I got it, it was making just under 11ftlbs but has decreased gradually in power to under 9ftlb.

I decided to get the parts I needed, seals and pump and set about stripping and rebuilding it, so got the gun apart, cleaned and relubed all the parts, the inertia weight was siezed so I freed that up,replaced o rings and applied silicon grease to them, I put about 5ml of oil and gearbox additive in the ram as people had advised, I polished the outside of the piston pumped it up to 11.3ftlbs and went to the range, the gun was leaking air and oil from the ram after every shot and power dropped down to 8 ish ft lbs again.

Stripped the gun again and couldn't see anything wrong with the o rings I had replaced but the leak was definitely coming from where the o rings seal the ram, could I have put to much oil in the ram or does anyone know why this could be happening?

Any help would be greatly appreciated.

[rhyslightnin]

I'm not aware anything other than a light smear of engine oil should go in the ram., Definitely not silicon! No silicon on metal to metal contact. I'd strip it put a bit of engine oil on it & put it back together personally, they need very little looking after normally...

[TonyL]

Hi Commando,

Sorry, I can't offer any advice on the gas ram repair, but a very warm welcome to the forum.

This is a great place for advice (as above) and I'm sure you'll have it sorted soon.

[bighit]

I'm not aware anything other than a light smear of engine oil should go in the ram., Definitely not silicon! No silicon on metal to metal contact. I'd strip it put a bit of engine oil on it & put it back together personally, they need very little looking after normally...

yep. I would not use silicon grease despite what others on here say. its not worth the risk. engine oil is the only oil I have ever seen advised .

[Shed tuner]

Engine oil is perfect.
Ref the seals, just try slightly tighter fitting o rings. Also make sure the ram is not scored.
Finally, make sure you fit the plastic backer to the seal, stops it extruding.
Hth -JB

Ps ditch the inertia weight, it all way OTT at 12 Fp.

[Commando]

[QUOTE=Jon Budd;7268511]Engine oil is perfect.
Ref the seals, just try slightly tighter fitting o rings. Also make sure the ram is not scored.
Finally, make sure you fit the plastic backer to the seal, stops it extruding.


Thanks for the replies, so silicon grease is no good for the metal? Im used to greasing o rings on my dive kit/regulators etc so naturally thought it best to grease the orings on the HW cylinder, if it's not advised though I'll take the grease off and just use a dab of engine oil as advised.

With regards to o rings, does anybody know a good source for these to enable me to get some better fitting ones? I got the new o rings from chambers, they are the proper part for the gun but maybe the is a better option?

I could not see any damage or scoring on the cylinder, would this scoring be obvious to see? If the cylinder where scored what would be the best course of action? Could it be polished etc?

Again thanks for your replies, I don't want to lose faith in this gun but I'm wondering whether I made the right choice with the 90, there is so many mixed opinions on the gas ram system and I'm a little disappointed that this problem must have been there when I bought the gun new.

[bighit]

I don't want to open a can of worms but here goes. Ben Taylor who was one of the theoben partners had a rifle come back to him that had seized up. silicon oil had been used. on metal to metal it in SOME cases cause the parts to gall on each other and size up.

you could try impact airguns who bought theoben when they "closed" down. they may have the seals you require.

they do servicing on the gas ram rifles too but its around £120 or so.

John knibbs http://www.airgunspares.com/store/ca...RAUCH/HW%2B90/

tawnado may do them too.

you could try a bearing supplier as most will do O-rings too. just give them the sizes you require.

paul

[Shed tuner]

Silicone on the o-rings is fine, but so is engine oil

Scoring - use your fingernail to feel for it. If so polish it out with fine emery / wet n dry

O-ring sizes, sorry, I can't remember - I just bought a few in a range of sizes close - 0.5mm difference - and used the ones that worked best. Spare o-rings are always useful, and it will only cost £2 for a bag of 10 from the bay.

My .177 90 is a great gun, really nice shot cycle (with inertia weight removed). Sure, the trigger isn't as good as a Rekord, but it's OK. And very accurate.

Rgds,
JB

[peddy]

Bin a while since I gave mine a full service, but sure the o rings will be correct, could the inlet valve be leaking instead? There's an o ring on that. Also I'd recommend leaving the inertia out all together, shoots much better without it. From memory I smeared a thin film of silicon grease on my o rings and a tea spoon of engine oil inside. Mines not lost any power in over 2 years. Persevere they are a great gun.

[Commando]

Thanks Paul,

That information is appreciated, I'm going to sort the ram tonight, I will see if the other set of o rings I have are a better fit, failing that I will acquire some more in a better size, also I will clean all the silicon off and just use engine oil in the ram.

As for the inertia weight I will keep that out for now as advised.

Thanks again for everyone's help, I will post my findings once I get the rifle back together and tested.

[Phil Russell]

I found some notes, not sure where from, but they say, for the HW90;

The two o-rings show 23,813 - 2,381 mm / imperial 15/16" - 3/32" (BS119)
The packer ring 22,225 - 2,381 / imperial 7/8" - 3/32" (BS118)
You may order at T.W. Chambers as follows:
o-ring sealing / HW-no. 2030 / Chambers no. OR066
back-up (packer) ring / HW-no. 2031 / Chambers no. PW128

In each case I believe the sizes will be inside diameter and the O ring cross section.
Might help if you decide to order rings ... might be wise to check / measure your original sizes though. If you took the originals to a bearing supplier they could measure them for you. They might sell very small numbers of rings but when I used to get rings from a local factor they suddenly decided to have a minimum order size for sizes they did not hold in stock. £10 comes to mind, so I reverted to t'bay.
Cheers, Phil

[Commando]

Cheers Phil,

I've found some o rings but have a choice of 90 hardness or 70?
They are nitrile o rings, which hardness would you recommend?

They are slightly smaller inner diameter and a little thicker which I believe will be beneficial as the orings I got from chambers 0r066 seem to be to lose fitting and presumably why my ram won't hold pressure.

Many thanks for every ones help.

James

[Shed tuner]

given the choice, I'd go 90

[Commando]

Also there is the option of Viton o rings, would these be more suitable?
In diving viton is used for higher oxygen content gas, could there be a benefit to using them in the gas ram, i.e. Better tolerance to wear etc?

[bighit]

Also there is the option of Viton o rings, would these be more suitable?
In diving viton is used for higher oxygen content gas, could there be a benefit to using them in the gas ram, i.e. Better tolerance to wear etc?

when I worked in offshore compressors the workshop manger always got stores to buy in Viton seals . he did say but I can't remember now.