Home made Innova piston seal

[Morningstar]

Well for all you Innova fans this is how I made a new Piston seal for my Innova , as asked for by Daliadigger and others.

Take out the internal spring and plunger from the Pump valve.

Next I measured the Pump valve for height (including old seal) then hacked out the old seal from the Pump assembly

Next I found some tubing the same size as the Pump chamber ( 19mm ) internal diameter. Cut this to the same length as the combined height of the Valve and seal and squared off both ends. Smoothed any burrs off and polished inside the one end for ½ inch down (depth of the seal). This will be the seal end of the mould.

Next Built up the threaded end of the Valve with insulating tape to make an even snug fit in the cut off tube, next built up the seal end with ptfe tape to make it a snug even fit too (because its slightly smaller than the seal diameter).

Cleaned the brass where the seal would go with some acetone to get any excess oil off it.
Then get some Vaseline and wipe over a very thin film around the inside of the smoothed tube to stop the silicone from adhering to the tube.

Drop valve it in the Tube stand the tube upright.
So now you should have a snug fitting valve sitting a seals depth down a Vaseline coated tube!

Get your silicone sealant and fill the seal end of the tube till its level with the top trying to make sure you have no air bubbles in it and is flat and level as possible.
Wait for the silcone to cure ! mine took 48 hours .

Next thing was to get the seal out! Just pushed from below! And out she popped. Remove insulating tape and ptfe and any odd bits of silicone.

Now you have to drill a hole down the centre of the seal to allow the air to reach the valve assembly. I used a 3 mm drill bit fitted to a Mini hobby dremel type drill to do mine, being careful not to drill through the bottom of the brass seat. blow through hole to make sure air can get to valve assembley.

Then you have to make the seal concave to fit the end of the brass air chamber, I did this using a diamond engraving tool that’s comes with the hobby kits .

And there you go! I reckon 30 minutes is all the time it took to do the work.
Mine works well! Smoother than a rubber seal too.

A word of note though!
I used low modulus silicone for the seal! I may try using a High modulus silicone next time because I think it may be closer in density to the original seal. I will keep experimenting though.

I hope this is intelligible to all concerned ! if you have any questions or suggestions please PM me
Regards Graham

[gedfinn 2]

Hi Mate, Its not hard enough ! IE short life ?
Measure Cylinder bore, Get out your PTFE, Machine to size, All dimensions ! ( Making the fit into the Pump arm head, Tight, ) Drop in boiling water & Fit, Job done, Good as new, Alternately, ? Machine new pump head, with Double O ring ( ALA Crossman Pistols " Modded ) Easy fix ! Cheers,

[Morningstar]

Hi Mate, Its not hard enough ! IE short life ?
Measure Cylinder bore, Get out your PTFE, Machine to size, All dimensions ! ( Making the fit into the Pump arm head, Tight, ) Drop in boiling water & Fit, Job done, Good as new, Alternately, ? Machine new pump head, with Double O ring ( ALA Crossman Pistols " Modded ) Easy fix ! Cheers,

Thanks geddfin! only trouble is, with me is access to a lathe.
I did try machining some rubber down on a pillar drill but It did'nt turn out to well if you pardon the pun. have made some of other bits for them out of 19mm brass bar using a pillar drill and files and emery paper. Stoneage I know but enjoyable.

[gedfinn 2]

Hiya mate, I know, you do what you can with what you have, ?
The brass pump heads with O, rings are very good, I do however prefer PTFE, I use it for Everything,
Machine Oversize, And leave it in the FREEZER !
When solid machine down to size, Works for Pump Heads ? pre-Charged Exhaust valves Etc, I use it on Most seals, Even Breech ! Etc, Cheers,,