Career/Sumatra help needed

[tinbum]

I've been having a fantastic time playing with a non-working Sumatra 500 today. I've skinned knuckles, used more deductive power than Sherlock hunting for the vaseline and made three different tools to render it down to its component parts.

Once apart I could find nothing wrong anywhere!

So it went back together with a little clean and fettle to see what occured. I put a few bar in the tank and it all cocked, fired and made encouraging "Bang!" noises. Happy days!

However, when I put 180 bar in nothing happens? I took the hammer assebly out and made another tool to reach into the exhaust valve and tapped it with a hammer: Pop!

So the valve is working, but the hammer assembly can't overcome the air pressure in the gun. I've tried different hammer settings and preloads, but as it was working before it mysteriously stopped I thought I'd ask the collectives advice before slinging it in a skip.

[tinbum]

Ok, I've wound the adjustable nose on the hammer right in to give the most travel and increased the preload by a lot. All I'm getting is a tiny poof! Not enough to fire the pellet.

I've had enough for tonight, but any ideas most welcome

[rancidtom]

I've not repaired any Sumatra 2500's but have repaired a few Career 707's. The 707's have an awful hammer stroke adjuster. This may be giving you trouble and not actually allowing a proper hammer strike on the valve? The last 707 I repaired had the hammer strike adjuster "overwound" by the owner causing a similar problem to the one it sounds like you have.
email me a pic or two of the hammer and stroke adjuster set-up, I may be able to point out where your problem is? PM me for my email...

[rovercoupe]

With a standard spring you should be able to preload the hammer spring by about 5mm with washers so might be worth trying to see if the spring is weak, i had to upgrade the spring after only getting 8ftlbs out of a standard spring no matter what i did, a £2 spring off fleabay worked perfectly!

[Jonjon79]

Could you attach a picture of the tiny poof please.

[tinbum]

Could you attach a picture of the tiny poof please.

Don't you think you've caused enough trouble?

[tinbum]

I've not repaired any Sumatra 2500's but have repaired a few Career 707's. The 707's have an awful hammer stroke adjuster. This may be giving you trouble and not actually allowing a proper hammer strike on the valve? The last 707 I repaired had the hammer strike adjuster "overwound" by the owner causing a similar problem to the one it sounds like you have.
email me a pic or two of the hammer and stroke adjuster set-up, I may be able to point out where your problem is? PM me for my email...

I'll have a look tomorrow and try it without the adjuster in place. I know the valve stem is clear as I've measured it and can actuate it with a rod and hammer