Seal sets Grrrrrrr!!!!

Jim-in-Darwen

Jim-in-Darwen

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A week ago I discovered that my RM8 had a slow leak. This is not an RM8 knocking post. It has behaved impeccably over the 10 to12 yrs I have owned it. This is about pkts of seals where “near enough” seems to be the packaging method. I am not going to mention any particular seal supplier as this seems pretty common. Now my example:-
Strip down air input, valve and regulator changing seals as I go. One off >> one on.
Attempting to find the corresponding seal can be a nightmare. Sometimes you can find one that looks to be close but sometimes nothing is anywhere near what you need. From where the air was escaping it was pretty clear it was going to be one of the seals either side of the Belville washer stack. I selected the two that best matched the originals (which were orange), reassembled and tested. I may as well have had no seals on as air escaped from the reg body as fast as I could put it in.
Strip down again and try another seal that looks close (there were no exact matches to the original sizes), reassemble and test. Same result - about as airtight as a sieve.
After four strip downs and rebuilds I put the original seals back in. Sealed straight away but still with the very slow leak.
If anyone can give me a source for correctly sized seals I would be obliged.

Let me say that I wish all suppliers were like HW100tuning who supply seals in individually labelled pkts with seals all correct sizes.

Jim
 
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… hope these help. 🙂
 
Hi - thanks for your response. I see from those exploded views that there are variations in the regulator. The piston in mine is as the 2nd and third image and has the 8x2 and 3.5x1.2 Orings. I fitted an 8x2 plus the nearest in the kit of rings to 3.5x1.2 and it leaked as though I had omitted the seals completely. I have refitted the original old rings and temporarily it seems to be holding pressure. However I know that I really need to get some correct size and just as importantly the correct hardness. The sellers of the Oring kits, in the main, supply just nitrile 70 shore rings for the RM8 but those two rings, from new, are harder and look to be a different material.
I am going to order a few 90 shore rings in a different material and give them a try.

Jim
 
Had this issue on 3 separate occasions with seals bought from B&K.
Seals of incorrect sizes on all 3 occasions

I feel able to name the supplier as I've taken the issue up with them and had no resolve
 
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Good luck @Jim-in-Darwen 👍

Agree with you about the RM8… incredibly accurate Airgun & given me the least issues, of all my PCP’s! 😳
Only changed O-Rings once due to being “frazzled”. (also over 10 years old)

Bought an O-Ring Kit on December 2024 from Silco on Ebay… & still holds air ok.

Silco Sports Ltd…

No idea if they supplied 70 or 90 shore, sorry guys.
 
Give @ped a message on here. In my experience, does excellent seal kits for less than the usual places. I've had several from him after a similar debacle with stuff from suppliers not being quite right
 
Naming no names in the interest of diplomacy I've found seal kits for various guns from various suppliers to range from spot on to absurdly inaccurate.

Somewhat unsurprisingly it seems you'll have more luck with kits from OEMs themselves (such as BSA kits from Knibbs although mine are more complete and cheaper ;) ) or if buying from a third party, kits for brands that publish the O-ring specs themselves so there's less to cock up (although you'll still see errors both on the part of the suppliers and the manufacturer's information).

The worst I've seen are those from third parties for less-well-known brands who don't publish any data - one example that springs to mind was IIRC for a Kral Empire (again from a supplier who'll remain nameless but has form IME) the contents of which was maybe 15% correct; the rest being laughably inaccurate.

This is partly why I buy my own seals, based on my own measurements / observations as it adds massive time to a job having to go through and check / second-guess every seal you've been supplied to ensure it's correct.. before in some cases having to just go out and buy correct replacements from somewhere else anyway.

The RM8 is a bit of a shit in this regard for a couple of reasons. Firstly sizes tend to be somewhat unusual in some cases, while Umarex also use alternatives to nitrile in many applications. This is beneficial in some ways as these less common materials (the green and orange O-rings) tend to last a fair bit longer than nitrile; but sourcing correct alternatives is more challenging.

On top of that it's a bit weird that the manufacturer chooses to fit more resileant seals to a rifle that in many other ways appears designed to be disposible.

Not that I've looked for a while but I don't recall finding anyone offering complete, correct O-ring kits for the RM8. Rothery are / were the supplier so it may be worth approaching them, but they won't deal with the public and a lot of the time suppliers will refuse to provide O-rings for regs; insisting on a complete replacement unit instead. Finally they won't be cheap and you'll probably have to go through a dealer and order each in isolation in the absence of any complete kit - because again the manufactuer would evidently rather it was chucked in the sea that repaired.

A quick shufti at what's curretly available suggests that all the usual suspects are supplying incorrect seals as they're all black so presumably Nitrile. Assuming they've managed to get the sizes correct these will probably work, but will have a shorter life than the originals.

Tbh I'd be inclined to leave the original coloured rings in place if they show no obvious damage / significant deformation and just replace the nitrile jobs as these should be easier to source and more likely to be responsible for the leak. I think I have plenty of the nitrile seals for these guns at home but few if any of the others due to the usual supply issues.

In a broader sense I'm happy to make up batches of O-rings for various guns if there's enough demand, I can get hold of them (my man is usually very good with sizes, less-so with materials) and I'm not stepping on anyone's toes as I know there are a few other guys on here also supplying kits :)
 
As said before none of the main airgun spares places in the uk buy in oem seals they make there own kits up, this includes knibbs.
And as such can get it wrong on sizes and material spec + not aware of factory changes in spec.
 
I was just congratulating myself that it had held 200bar with no leak for over 12hrs and decided to chrono to check all was well.
4ftlb’s and I had made no change to the hammer spring. What I could feel was a blast of air coming from around where the grub screw restricts the transfer port. Suddenly a big bang and all the air was dumped out of the barrel. I have some Viton seals coming for the regulator on Monday so going to shelve this for now.

Jim
 
i think Mick(the logunator) used to do rm8 seals Jim
 
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