Random dieseling, xs B12

[MarkBrumbaugh]

I polished the trigger, and lube tuned.   Shoots great, but once in a while I get a loud pop...and sometimes it does not expel the pellet.   I'm guessing the piston seal must have a flaw.   What should I order as a replacement.   Btw...it was nearly impossible to get the sleeve back in the pivot.  Any trick for that?

[mikeiniowa]

you need a new piston seal or you have over lubed the rifle, they take a 25mm seal.If you can see the lube in the tube you have to much, should not really be able to see it but only feel it, just a thin coating on the seal, once again only be able to feel it, at the rear of the piston on the skirt you can have a light coating you can see. To get the barrel back on the easy way is to get the barrel in the forks and get the holes to line up as close as possible, then insert a small shaft, screwdriver or punch and cock the rifle...make usre the safety stays on, then realign the holes and insert the sleeve, load and fire then finish...

[MarkBrumbaugh]

Thanks mike.   I didn't overlube, but I didn't clean out the cylinder either.  The curious thing was it only dieseled after 15-20 shots, and then would quit for a while...and then a couple more loud pops....and quit again.   Sometimes when it dieseled, it would not even fire the pellet, so I figured the seal must be bad.   It only diesels rarely, so something must be occasionally leaking in.  I'll order a 25 mm vortek seal.

[MarkBrumbaugh]

Thanks mike.   I only used krytox, which is inert, and moly paste very
 sparingly on the piston.  Obviously something is making a large explosion about twice in a row every twenty shots.

[mikeiniowa]

I have the seals you need...cost is minimal...

[MarkBrumbaugh]

I have the seals you need...cost is minimal...

Send me a couple...my email address is mark.brumbaugh@sbcglobal.net to take care of business.

[LAalex]

If you didn't clean out the compression tube, then whatever lube was in there from before has now been squeegied to the front of the tube by the piston seal when you reinstalled the piston. 

Scotty

[MarkBrumbaugh]

If you didn't clean out the compression tube, then whatever lube was in there from before has now been squeegied to the front of the tube by the piston seal when you reinstalled the piston. 

Scotty

I think you are right...but seems strange it only detonates once in 20.   I think the seal has to be bad

[LAalex]

You are right, it does seem a bit strange.  Maybe if the seal is nicked, the conditions for combustion are not present every time because of fluctuations in the pressure level?  Just a thought.  Hopefully someone with a better knowledge of the physics involved can chime in with some good information.  In any case, I feel fairly confident that a good cleaning and reseal will eliminate the trouble.  With the exception of complaints involving the trigger, these little rifles seem to be very well-liked.

Scotty

[mikeiniowa]

deburr the tube well so the seal can do it's job right, seal kit on the way soon...polish up the trigger and the tang carefully and lube...side to side play in the trigger can be cured using shims

[MarkBrumbaugh]

Yeah, I got the trigger very acceptable.   Just need to find new piston seal.   I'm ready to brake hone the cylinder.