Did I blow a seal on my FWB 601?

DWood · Post by **DWood** » Tue Apr 01, 2014 4:53 pm

I was doing a little practice in the back yard today and my 601 broke. When I was on the upstroke of the pump, there was a small pop sound and then on the downstroke there was air coming out of the valve hole below the breach. The trigger didnt set, so I tried again and it worked fine the second time. The problem happened the same way on the next pump and then was back to normal again after that. I put it up and decided to find out what I could. I found nothing so far on this issue. Any help would be appreciated.

BenHHH · Post by **BenHHH** » Thu Apr 03, 2014 3:49 am

Hello
I think you have to verify the valve (1750.212.1 and particularly its seal.
or the cylinder's valve...

45ACP223 · Post by **45ACP223** » Sat Apr 05, 2014 10:19 am

There are only really two seals that usually go over time. The main compression piston seal which you can see when you open the cocking arm (usually, green, blue, or red), and the valve seal behind the valve block (4 screws) in the breech area. You have a few o-rings but they usually never fail. If it pops on opening the cocking arm, you aren't getting all of the air out of the valve during firing and it could be the valve seal or gunk build up in that area. If you cock it and have low power or hear air leaking it's the main piston seal. These are very easy rifles to work on, get an exploded view on-line and you can figure it out. Pilkguns should be able to sell you the parts you need or send me a PM if you can't find any.

Rover · Post by **Rover** » Sat Apr 05, 2014 4:42 pm

I recall the same thing happening to my Pardini K58 SSP air pistol. An easy cure was to increase the pressure on the striker spring (a simple turn of a screw). This then released ALL the air at discharge; no more "pop."

Assuming this is your problem.

DWood · Post by **DWood** » Mon Apr 07, 2014 10:06 pm

Thanks for the information. I'll tear it down tomorrow and see if I can find out if the issue is a seal, gunk, or the striker spring.

DWood · Post by **DWood** » Tue Apr 08, 2014 10:42 am

Well, I took the 601 apart today and got it clean up a bit. Now I have a problem. The barrel band/cylinder cap won't slide back on. I've tried greasing the inside and lightly tapping it on with a rubber mallet, but it just won't fit. Is there anything I should be doing to get this thing on?

45ACP223 · Post by **45ACP223** » Wed Apr 09, 2014 9:33 pm

Sent you a PM, did you get it straightened out?

dpr · Post by **dpr** » Fri May 16, 2014 10:36 pm

I'm glad this post came up. I just had the same problem. I took the valve apart and found small chunks of the piston seal in the valve assembly. Looks like I'll be calling our host on Monday for some fresh parts. What lube do you use on the piston seal?

45ACP223 · Post by **45ACP223** » Tue Jun 10, 2014 10:11 pm

Two schools of thought on that question.

1. FWB Manual diagram shows a drop or two of lube (use FWB Grease only).

2. Master Air Gunsmith said FWB told him to not lube the piston seal after the initial factory lube, shoot it until it wears out and replace. The seal is pretty hard material and lasts a long time.