Diana 340 N- Tech.

[Novagun]

My new Diana 340 has now had about  800  to 1000 pellets through it. It is still dieseling, although in the beginning it did not appear to do so. Dieseling is not bad but there is still smoke after a shot. Sometimes there is more smoke than others, which suggests to me that there is still excess manufacturers grease in the compression chamber. Despite that the rifle is surprisingly quiet but putting out good power. Can't  be specific because I do not have a chrony. I really don't want one but may have to yield sooner or later. The rifle at 50mms range drives a pellet 22 mms into Pinus Radiata. My most powerful rifle.
There is a sentence in the rifle pamphlet that says that dismantling will void the warranty so a clean and re-lube is out for the time being.
The other thing I have noticed is that the rifle seems to have changed its preferred pellet. Used to like H&N FTT but now seems to like JSB Exact. Not much change in weight but some.
Will just have to carry on see what develops.

[Yogi]

Yes, my 340-N tec still diesels a little.  I i of like it.
Hope you have the hogback stock?  Mine loves the 16 grain Air Arms pellets.

-Y

[Roadworthy]

If your gun is still dieseling after that many shots you should have burned off any factory lubes ages ago.  You may have a weak piston seal.  If the seal does not seal properly any lubricant behind the seal may not be scraped from the compression tube but may remain on the walls to be detonated when the piston moves forward during firing.  Seal replacement does require dismantling the gun thereby voiding your warranty.  That is my suspicion due to having the same issue with my TX 200.

[Toxylon]

My experience with Dianas, Weihrauchs and Walthers is that they will diesel forever (1 000 shots +), unless the innards are thoroughly cleaned up and stingily re-lubed.  One will also get enhanced muzzle velocities for all that time, so I take "I've shot the new gun 200 times and the dieseling has subsided, so here's the chrono stats"-type comments with a big grain of salt.

After well over 1200 pellets, my LGV shot at <18 J. After a cleanup and minimal relube the ME dropped to <16 J. For all that time (and who knows how much longer), the gun had a dieseling-enchanced power profile.

My HW95 never stopped smelling of burnt oil, when at 1200 pellets I sold it.

My D48, where the piston seal basically cannot be nicked, would actually throw the occasional four-inch muzzle flash once in a while at 800+ pellets.  So, smoke at 800+ is nothing out of the ordinary.