Fwb600 problem

[NeilnrLincoln]

Hi all.
I've got an fwb600 which is lovely to shoot & so accurate. But sometimes when cocking it it releases the air pressure as you start to return the lever, like the piston seal isn't sealing & allows the air past instead of compressing it. Sometimes it can work perfectly time after time & sometimes it'll fail several times in a row. It always works fine once it has compressed a charge.
Is it a matter of stripping & replacing the seals or is there anything else to try?
Thanks.
Neil.

[Drew451]

Mine did exactly the same until it began to fail to compress air altogether. I assumed it was the piston seal but it turned out that it was the only seal that wasn't shot. Diagnosis and repair were carried out by Laceys Shooting Services- first class service by Chris.
I would add that I do not know which seal failed first as I switched over to another gun and left the 600 in a state of disrepair for some time. So its likely that the other seals may have followed the offending one/ones.

[NeilnrLincoln]

It does look like the piston seal has been replaced at some point as you can see it's a blue one when you cock the rifle.
I had intended to strip it down & replace all the seals & ordered a set of replacements from Foest Europa in Germany but that was a month ago & it looks like they've got lost in the post, I've been in touch with them & they've said they're out of stock now & Feinwerkbau cant supply any more until some time in May due to the corona virus

[PhatMan]

Neil,

You may be able to eek a little more life by lubing the seal.

Open cocking lever fully, and put a couple of drops of synthetic motor-cycle fork oil (or other suitable oil) onto the visible part of the seal, and allow oil to flow round seal.

Operate, load and fire the rifle a few times - any excess oil will be blown out of the system via the barrel, and will lube all the intermediate seals.

( no it does not do the rifle any harm, despite what others may tell you )

Nikkonos (https://www.bayofflea.co.uk/usr/nikk...p2047675.l2559) of Bay Of Flea can supply the 600 seals (amend the URL to correct place ):

https://www.bayofflea.co.uk/itm/Feinwerkbau-Mod-600-601-Basic-kit-Crank-lever-Air-rifle-Seals-Service-kit-/373022063315?hash=item56d9d8fad3

( Contact him first about whether he is shipping to the UK during the Covid-19 hysteria )

Have fun

Best regards

Russ

[NeilnrLincoln]

I'll give that a try in the short term until I can get some seals.
Thanks for that Russ.

[Jimlad]

City Air Weapons carry FWB spares

[NeilnrLincoln]

Well, I finally received a set of seals for the FWB600, minus the piston seal as this is out of stock & following on later. I thought as the piston seal that's fitted appears to be a modern replacement I'd go ahead & replace the rest of the seals.
I stripped her down, cleaned everything up & fitted all new seals (obviously refitting the original piston seal, which looked fine), relubed sparingly with the correct Feinwerkbau grease & reassembled. The only slight issue I could find was a little rust on the valve but this was at the spring side not seal side & I cleaned it up. Tried it once reassembled and....

pfft, it still only compresses a charge when it feels like it & almost never on the first stroke of the lever. Looks like the piston seal is goosed after all, so it's back in the cabinet awaiting the eventual delivery of the final seal, hopefully that'll fix it.

[abellringer]

This is symptomatic with impending valve seal failure; if the piston head is worn /damaged then air will just bleed out behind the piston. When the valve seal is starting to split up, you get all sorts of erratic behaviour, very common ids the effect of the cocking lever kicking back on opening as all the previous air is not expelled. I would look at the valve area first again, check the little brass cone is clean and not scratched, the spring is not failed, and don't put any grease in there on assembly. Once the valve is sorted you can compress, shoot / check power; then re cock and leave for an hour, repeat, then repeat over 24 hrs; this should confirm piston head condition. Any more info needed, PM me by all means.

[10/10]

It is nearly always the valve seal which decays, and you can get at this from the back.
I am pretty sure it is the same seal as the FWB 100- 102 103 it will some times let by untill the valve seats

[NeilnrLincoln]

Sorted now, thankyou. All seals replaced & it turned out to be the cocking link, the 90 degree bend at the end of the link had got very slightly bent so it just wasn't quite travelling far enough to set the trigger every time.

[PhatMan]

Neil,

The link is adjustable for 'length' on the '602 - is it also so on the 600 ?

Have fun & a good weekend

Best regards

Russ

[NeilnrLincoln]

Unfortunately no, the 600 has a one piece cocking link so I had to just bend the elbow at the end slightly & now it cocks every time.