A question for those who own the Crosman Quest
I think there maybe some confusion here. The Crosman Quest is the Chinese, Xisico B-19. Crosman bought the rights to the B-19 a while back, tickled it up abit with different sights, better bluing and stock finish and put their name on it. I have worked on both the Quest 500 and the 1000. They do share the same internals except for the piston. As explained previously, the 500 piston is longer giving it less swept volume. The tarantula seems to be the spring of choice for these rifles but without a fitted guide, I wouldn't waste my time. My Quest 1000 had the stock spring with an appex seal and fitted guide and it would throw cpl's over the chrony at 910-915fps. That seems to be about the norm for these rifles, although some have claimed upto 930-940fps. Like all airguns, it depends on the gun.
Does the plastic plug piece slip off the guide on the Quest? I'm referring to part #16 in the parts diagram http://www.xisicousa.com/xs-b19.html This is the part that I have heard breaking on the rifles. This part of the guide rod could be replaced with a stronger material. That's likely what tuners are doing but maybe the entire rod is replaced. Comments?
It's not surprising that the Quest has a soft piston and receiver (as mentioned by Charlie DeTuna). Most Chinese airguns are soft metal. I wouldn't be surprised if the Slavias were the same. I know my HW45 has a very hard piston because I tried to polish the thing with emery paper. I used a drum sander plug in the end of the piston and spun it on a drill. The paper barely polished the piston surface. Very hard metal. I would think the Dianas are hard too but I did not check the ones that I had.
Todd
It's not surprising that the Quest has a soft piston and receiver (as mentioned by Charlie DeTuna). Most Chinese airguns are soft metal. I wouldn't be surprised if the Slavias were the same. I know my HW45 has a very hard piston because I tried to polish the thing with emery paper. I used a drum sander plug in the end of the piston and spun it on a drill. The paper barely polished the piston surface. Very hard metal. I would think the Dianas are hard too but I did not check the ones that I had.
Todd
I purchased my Quest 1000 new. I couldn't handle the twang! The gun was rough when cocking also. So that's when it went under the knife. It's not hard to make these gun smooth. I machined the guide, installed an appex seal and deburred what I could and cleaned up the compression chamber as mentioned before. I enjoy this sort of thing so it wasn't a big deal. I did not find the piston of the Quest soft by any means. I tried to fix the piston out of the Quest 500 I had brought to me (young guy with power in mind 
) and I found that the metal of the piston was quite hard. Then after I found that a new one from Crosman was only around $12.00 IIRC, I was ticked I spent the time on it. (Can you believe the trigger assembly is only $13.00+/-!!!)
I have never shot a Diana 34. The Quest is jumpier than my B-20 which suprised me. It is by no means "teeth shattering"! I shot a Gamo rated at 1000 fps and it was comparable to it. The part you are refering to in the diagram does slip off. That is the piece that was pictured earlier. This is the first time I've heard of this, but sounds like a weak point for sure. I have a spare one here and can't see why it would break. Although, as I mentioned before, the end of the spring butts up against this piece and in my opinion there should be a shim or washer to separate them. The spring torques everytime you cock the gun, so to have it twist on the plastic, even the little that it does, I can't see how it wouldn't chew it up. WOW! This post was way to long!
) and I found that the metal of the piston was quite hard. Then after I found that a new one from Crosman was only around $12.00 IIRC, I was ticked I spent the time on it. (Can you believe the trigger assembly is only $13.00+/-!!!) I have never shot a Diana 34. The Quest is jumpier than my B-20 which suprised me. It is by no means "teeth shattering"! I shot a Gamo rated at 1000 fps and it was comparable to it. The part you are refering to in the diagram does slip off. That is the piece that was pictured earlier. This is the first time I've heard of this, but sounds like a weak point for sure. I have a spare one here and can't see why it would break. Although, as I mentioned before, the end of the spring butts up against this piece and in my opinion there should be a shim or washer to separate them. The spring torques everytime you cock the gun, so to have it twist on the plastic, even the little that it does, I can't see how it wouldn't chew it up. WOW! This post was way to long!