Bolt stick, chuffing & double firing on Classic vaslve

[Hook]

I acquired this beautiful Classic 68 this weekend - previous owner could not get it to fire. I gave it lots and lots of oil and it began firing again! However, it will chuff or bvolt stick every 2-3 shots. If I increase velocity, it starts to double fire.

I've got a Classic parts kit, but am unfamiliar with the Classic valve. Any pointers?

[hill160881]

New orings in the on off assembly and powertube sounds like a good idea. Also check the specs on the marker, and make sure they re at there stock settings.

All the specs are here and just a few threads up.

http://www.automags.org/forums/showthread.php?t=67604

[athomas]

A good cleaning is always helpful when starting with any previously owned gun. Replace all the orings at this time. It will eliminate any doubts as to what the problems might be. Change the bolt spring. When they get weak, they can cause bolt stick issues.

[Hook]

Good thing I have a spare spring!

[Spider-TW]

Check on your rail bushing,

http://store.airgundesignsusa.com/index.cfm?fuseaction=catalog.prodInfo&productID=403&categoryID=92

Missing rail bushings or bent field strip screws can make some strange behavior.

[Hook]

Rail bushing is in place and not missing. Field strip screw is nice and straight. I even tried a spare one. I stripped down the valved, gave it a good clean, changed every single o-ring in the valve and on/off, as well as installing a new spring. I then gave it lots of autolube and it does the same thing as before.

Any ideas what I can try next?

[hill160881]

Is the body origional, painted or powder-coated? On off pin length? Powertube type(spring or spacer type)?

[Hook]

It's an original body. Power tube has a brass spacer. No clue on on/off pin length, I don't have calipers to measure the length.

*edit*

I forgot to mention this the valve has mismatching serials. Maybe that is part of the issue.

[Spider-TW]

Are you testing without the barrel?

Does the sear move freely?

Good air supply?

[Hook]

Are you testing without the barrel?

Does the sear move freely?

Good air supply?

With barrel, sear does move freely, using a full Ninja 50/4500 at 850psi

[Spider-TW]

You might inspect the barrel breach for rubbing and try shooting it without the barrel, just to rule it out.

Frame screw tensions about right?

[athomas]

The serial number mismatch shouldn't be an issue.

What type of on-off top does it have? Is it the universal top (same on both ends) or the one with the X cut on one end. If it is the universal top, it doesn't have a direction. If it is the older X cut, then the flat part has to go against the 2 top orings and the X goes against the lower section of the on-off.

Check the sear for wear at the tip. It should be nice and sharp. If there is any rounding, or a noticeable ledge where the bolt sits, it could be an indication that the sear is worn out.

Fire the gun and hold the trigger in. Does it leak out the front when you do this? If not, then all is well with the on-off orings. If it leaks, then there is an on-off issue.

[Hook]

The on-off top looks like the universal one. The sear dosn't look worn-out and looks sharp, but there was a some accumulated grime on the sear hook and on the bolt lip.

The marker does not leak when I hold the trigger in. In fact, when it does leak or chuff, holding the trigger will stop it from leaking. Repeatedly pressing the trigger usually helps the bolt to fully reset itself and stop the leak.

[Ando]

As Spider suggested. Try firing it without the barrel. could have something wrong with the barrel, maybe the detents. If they're wire ones they're prone to snaping off and the lip of the bolt will sometimes catch on it.

Other then that, you could have a worn reg spring pack. You've pretty much done everything to fix this issue. If you have another classic, try swapping parts till you find the problem.

[Hook]

Same issue when firing without barrel. At this point I think I'll just scour the forums for a used classic valve. They go for fairly cheap.

Thanks for the help guys!