Help with an Airsporter

[gp-bear]

I have an Airsporter MK6 ( I think ) Ser# EN1056 that has seen better days .
Trying to fix this for a freind , but I am stumped .
The piston head is siezed in the tube and I cannot remove the piston or of course the head . There is some side movement in the piston , rotates left to right a tiny bit , but that is it .
Any thought on how to get this out .

Ted

[MattyBoy]

Yeah late 70's Mk VI

Soemone will tell you how to sort it I am sure#

Cheers

[flatrajectory]

Hi Ted,
This is a common problem on the late Airsporters fitted with a nylon piston head. What happens is the nylon swells/expands and seizes into the cylinder.
The best method I have found is to remove the loading tap, then squirt some wd40 or silicone oil or similar lube into the transfer port via the hole where the loading tap was,
Then, using a long piece of steel rod ( such as .177 cleaning rod ), push this down the barrel into the cylinder through the transfer port and gently keep tapping it with a small hammer to move the piston down the cylinder. Keep spraying lubricant into the cylinder as the piston moves down. PLEASE NOTE : the rod you use must be thin enough to go through the transfer port in the cylinder, About 3.5 - 4 mm from memory.
good luck,
Pete.

[ggggr]

I have an Airsporter MK6 ( I think ) Ser# EN1056 that has seen better days .
Trying to fix this for a freind , but I am stumped .
The piston head is siezed in the tube and I cannot remove the piston or of course the head . There is some side movement in the piston , rotates left to right a tiny bit , but that is it .
Any thought on how to get this out .

Ted

It may have a synthetic head which swell up over the years and is not helped by the piston buffer breaking up. I would be tempted to put some oil down the cylinder and then reassemble the gun without the mainspring. If you can get it to cock (or at least move a bit ) without too much force then you should not have much of a problem. If it will not move like this then strip it again and tap the piston with an aluminium rod. If you can move it far enough to see the piston head then you can ease the head with a file or wet or dry paper. If the head is aluminium then try cool the action in a deep freezer (the alloy should contract more than the steel) and then tap it out. I did a synthetic head mk5 by using oil and picking out the bits of buffer washer as it broke up and tapping the piston(took about 1hr).I actually cleaned up the head and reused it. If the piston does move back a bit, then after picking any washer bits out, use more oil and then slide the piston forwards again. This (should) stop bits of washer jamming under the piston. I hope this helps. Ps with the tap closed, an airline down the barrel might shift it.

[gp-bear]

Thanks for the tip , I will start soaking this in oil and let yo know what happens .

Ted

[oliver13]

Hi,

Without having done this, maybe I should stay out of the thread but I note the suggestion to use an airline to shift it?

If you going to the trouble of devising a method to tie-in an airline somehow, I would suggest do it instead with a grease nipple - & use a grease gun to shift the piston?

Mainly I am thinking an airline's only going to be good for about 7 bar, but even so, if something did let go with everything pressurised it could be quite dramatic - probably leave your ears ringing anyway... That won't happen if it is full of grease instead.

Regards

[edbear2]

I had this recently with a Mercury ......The buffer washer had disintegrated and turned to a gooey lump, and the gun was rock solid and would not cock......I used 'mouse milk' (really!)........A brilliant penetrating oil, the like of which I have never seen before....I don't know if it can be got over here, I was lucky enough to have first shout at a 'package' of aircraft lubes etc. and there were a couple of small bottles of this stuff in there.

Anyway.......plusgas would be a good alternative, I soaked the piston head area overnight, and used an aluminium drift in the piston slot to knock back the piston until the buffer mess was exposed......It was super tight, unlike anything I have come across before!

I then used a scriber and more oil to break up all I could see of the buffer and repeated again and again until all was free........the cylinder was perfect, it was just the buffer that had caused all the grief.....the washer dust had the smell of a cellulose type plastic, so I tried some acetone on the dust and came to the conclusion that this may be a quicker fix if ever I was unlucky enough to have this job again.....obviously this is highly flammable, so take all precautions if giving it a go....It may well attack the piston head as well thinking about it

P.S........re the airline.......when, and if this moves it, you will have something like a small lethal cannon shell flying around the place!!!!!...... unless you point the job into say a dustbin packed with old paper / bubble wrap etc. The grease gun idea would be more controllable, but getting a pressure tight fitting may be a drama.......I found the shock of repeated blows with a mallet the best way myself.

[oliver13]

Hi,

Just another thought, what about heat?

I don't mean burn the thing out as such, just enough to soften the plastic?

A concern could be expansion of the plastic, which would be significant & may even stretch the compression cylinder - does anyone have anything reassuring to say about this?

Sorry, but again not something I've actually done myself - hopefully one of the less destructive ideas will succeed?

Regards

[gp-bear]

The piston and head are out .
What worked best was soaking it with WD-40 and gun oil for a couple of days .
I tapped the piston back and forth with brass rods and used dental picks to remove the old seals once it had come back far enough .
I think this was the safest method .

Thanks for the tips .

Ted

[corvids]

I used 'mouse milk' (really!)........A brilliant penetrating oil, the like of which I have never seen before....I don't know if it can be got over here,

Yes you can, it's not cheap at £13ish + postage http://www.lasaero.com/site/products...e?id=O03SH29N9 - A lot of useful stuff here as well.