Biakal IZH-46M Piston setting?

[Cynabal]

Ok I recently got a IZH-46M and after removing the grips and shaping them to my hand and then finishing off with linseed oil, I decided to strip the gun down to give it fresh lube, and familiarize myself with the gun and how it works.

When I removed the piston from the cylinder I noticed the piston itself is screwed into the linkage. The end of the linkage is threaded with 4 notches cut in at 2, 4, 8 and 10 o'clock and the piston has a hole at the back where a small screw goes in and holds the piston in place.

Picture

I took note of how far the piston was screwed in and which notch the screw was aligned with so I could put it back how it was, but is was thinking if you can screw the piston in and out of the linkage doesn’t this affect the compression of air?

If the piston was screwed right into the linkage then the distance from the head of the piston and the back of the compression cylinder would be greater and I'm guessing therefore the air wouldn’t be compressed as much when its cocked, and I'm thinking is the opposite also true, if the piston it not screwed as far into the linkage then the distance between the back of the compression cylinder would be less and the air would be under more compression?

I would have tried this theory out but I don’t own a chrono, and I don’t want to damage my new IZH-46M but I'm wondering if anyone here knows about this? As its obvious that the piston is designed to be adjusted hence the 4 notches.

[derekm]

This may help, if you use a bit of understanding and mechanical sympathy.

The Daisy 7x7s work on the same principle and with them, if the gun is uncocked and the charging/cocking lever is cycled without actually pumping, the piston will touch the end of the cylinder with the lever 3/4" to 1 1/4" from it's closed position.

ie. it goes up to 1 1/4" "over centre" and in practice, cocks with a slight final clunk.

Sorry for the description, but if you have already used the gun a little, you will understand what I am trying to get across.

[Cynabal]

Im guessin by your description ideally you would want to set it so the piston just touches the end of the cylinder when its fully closed. the charging arm does kinda pop open a little when the catch disengages, im guessin this is due to the piston head being under a little compression and when it releases as its rubber it pop's the charging handle a little as the piston head regains its shape.

[derekm]

That's about right. Because the dimensions are roughly the same, the Daisy setting of up to 1 1/4" is likely to be OK. Just go gently and not apply a lot of force and you should be OK.

Is there nothing in the manual about this setting?

You could try asking Pilkguns http://www.pilkguns.com/

or asking on their forum Target Talk http://www.targettalk.org/viewforum....days=0&start=0

It's populated by fairly high level pistol men, but they will always answer the most basic questions and offer lots of help.

[Iain K D]

I don't know the reason for this (the shorter-cylinder 46 has the same piston), it might be meant as a way of adjusting the compression a bit, I wonder though if it might not just be a way of keeping the exterior of the piston intact and a smooth bearing surface.

I think I've got mine set so that the piston seal doesn't quite touch the end of the cylinder. One way of getting the feel for this is to remove the pump lever (the rearmost of the two pivot pins at the front of the cylinder), which is not physically connected to the piston/toggle, and, with the outlet valve open pushing the piston in by pressing on the shorter arm of the toggle (part no. 50). There's then less to remove to get the piston out again if need be.

I'm sure the rubber piston seal wouldn't be damaged, but I was worried about putting the pivots in the toggle under undue strain as it reaches and then passes (as it were) top dead centre.

Iain

[Cynabal]

I don't know the reason for this (the shorter-cylinder 46 has the same piston), it might be meant as a way of adjusting the compression a bit, I wonder though if it might not just be a way of keeping the exterior of the piston intact and a smooth bearing surface.

I think I've got mine set so that the piston seal doesn't quite touch the end of the cylinder. One way of getting the feel for this is to remove the pump lever (the rearmost of the two pivot pins at the front of the cylinder), which is not physically connected to the piston/toggle, and, with the outlet valve open pushing the piston in by pressing on the shorter arm of the toggle (part no. 50). There's then less to remove to get the piston out again if need be.

I'm sure the rubber piston seal wouldn't be damaged, but I was worried about putting the pivots in the toggle under undue strain as it reaches and then passes (as it were) top dead centre.

Iain

Funny you posted this, i just got done adjusting the piston again so it dosent quite touch the end of the cylinder, i figured id rather have the piston seal last longer than little more compression.

[derekm]

I came across this on the Target Talk forum:

http://www.airguninfo.com/46index.shtml

Haven't read through it, but it's all Izzy and maybe the correct answer for your question is there.