Sunday, 14 April 2013

Sharp Innova Dissassembly and Reassembly, Saved From The Dustbin

For a more detailed look at the Sharp Innova check out my more recent blogs '.22 Sharp Innova a restoration project' HERE  HEREHERE , HERE, or HERE

In my last order from J Knibbs  i decided to see if i could resurrect the Innova and got the complete seal and washer set, and a replacement pump head seal. With the back corner of the breech block chipped off exposing the bolt catch and unable to keep the spring in place, I wondered if it was beyond repair at all. But when I pushed the catch up and it held the bolt I thought why not, besides, I could always attach a small plate to hold the catch spring in place or something. But first sort out the valve as it would only hold under one pump of pressure which would slowly leak out, it sounded like the inlet valve was broken but it had to be taken apart to see. I had heard good reports about how good these Japanese Multi-pumps were, dispite all the plastic used to make them.

Step one was to open the pump arm all the way open so no air was compressed in the compression tube, this makes it a lot easier to remove the pump rod unit. You can remove the pump cylinder and exhaust valve without taking the front end apart, but i decided to dissassemble it so i could clean and polish as much as i could.

front hollow pin, though the photo was taken when i reassembled

I tapped out the front hollow pin which holds the front unit to the compression tube, i then removed the hinge pin next to it. This is held in place with a circlip and holds the pump arm and the front unit inside the compression tube, it is made of solid plastic and could now be slipped off the tube, inner barrel, and plastic outer barrel.

Pin holding the underlever to the piston rod unit coming out through the hole for the pump arm pin

With the pump arm removed i could pull the piston rod unit back and disconnect the underlever, tapping the connecting pin through the pump arm hole. The pin does not line up perfectly with the cylinder holes, with one side lined up 3/4 of the pin was visible on the opposite side and needed a smaller pin to tap it out. The piston rod unit could now come out easily, not only did i need to replace the pump head seal but the rod was in need of straightening out a little. There was adjustment at both ends of the rod, so after clamping the rod in a vice for half a day to remove some of the warp i made some adjustments to lengthen the pump rod unit.

 The brass hinge end was given two complete turns after releasing the locking nut and then locked back again, and the seal end was given three complete turns again with the locking nut to secure it.So now to get to the exhaust valve in the compression chamber inside the breech, I thought removing the stock would be a good idea for a start.

Brass collar in front of the trigger with the grub screw square nut set in the breech housing in front of that
By removing the front crosshead screw on the trigger guard the stock was removed revealing a brass collar, which i unscrewed to reveal a screw thread sticking out of the breech unit, this has a slot for a flat head screw driver and secures the valve in the correct place in the compression tube. In front was a grub screw which goes through a square bolt in the receiver body to press against a metal spacer which forces the compression tube upwards in it's hole in the receiver, which has a tad larger diameter. This seals the tube and valve to the barrel, but unfortunately no spacer  slipped out when the screws were removed as it was missing. Anyway the compression tube came out easily with the breech seal O ring in place, the O ring was put aside and the new one from the seal kit was sized and made ready for when it was reassembled.

Transfer port O ring seal sitting between the compression cylinder and breech unit, no spacer though.
Getting the exhaust valve assembly out was pretty simple with no pump arm still attached to accidently close and send parts flying out while dismantling, i made this mistake a while back much to my regret. The exhaust valve back guide was just under finger tight and unscrewed easily but only the exhaust valve spring and the spacer sleeve came out, there was no bumper or bumper plate but luckily these items came with the seal kit. Pushing a piece of dowel down the front of the compression tube the valve unit slipped out the back, if the pump arm was still connected you could slowly close this to push the valve out.
Valve air chamber and guide with firing pin, spacer, exhaust valve spring, and exhaust valve back guide

The valve unit consists of the brass front end air chamber screwed to the brass valve guide block with an O ring to seal them, when unscrewing them its best to be careful of the valve spring that holds the inlet valve ball from flying out. Stone me! They were hard to get apart, in the end i had to use two sets of mole grips and twist them because they were joined so tightThe mole grips left marks on both parts, but i sanded them down with some wet and dry till the were smooth. Now i could unscrew with my fingers and carefully caught the spring and ball in my palm and put them aside, i teased the old O ring out with small flat head screwdriver after sliding the firing pin out. I removed the small brass collar and the firing pin O ring seal from inside the guide, cleaned the brass parts with white spirit, put in the new O ring seal with a spot of Molicote and brass collar, then put on the new valve O ring, and put that aside ready to screw back onto the air chamber.

The air chamber itself Has a delrin seat for the inlet valve that is held in place with a screw in collar  and is a guide for the valve spring, it has two slots opposite each other at the top so a flat blade  would unscrew it. Shining a torch down the chamber i could see small nicks on the delrin seat explaining why it would not hold air, there was no replacement delrin seat but i then i noticed an unaccounted fat do-nut O ring in the seal kit that would fit perfectly in the hole for the collar to sit on. So i unscrewed the collar and teased the seat out with a pin from the outside of the air inlet hole, removed the outer seal, and cleaned all the brass up with white spirit. Putting it back together was a case of popping in the new do-nut ring, screwing in the collar to seat it comfortably, cleaning the ball and dropping it in place with the spring on top, then screwing the guide back into the air chamber so they joined but were not over tight. Problem sorted hopefully.

I then cleaned the compression cylinder with OOO wire wool and white spirit on the end of a piece of dowel, then polished the chamber with autosol as i don't have any GN paste. I slid the bumper on the longest side of the firing pin and pushed it against the collar in the middle, the other shorter side was smeared with molicote and inserted into valve guide. Making sure the transfer port and screw hole were lined up correctly i put a smear of molicote on the O ring and inserted the valve into the compression chamber until the holes were aligned, in went the exhaust valve spring followed by the spacer with the new bumper plate snuggley fitting inside the rear,and finally the exhaust valve back guide was screwed back in less than finger tight into the rear of the compression cylinder so it was flush with the firing pin.

I smeared a touch of molicote to one side of the transfer port seal and put it in place, then with the trigger pulled back i inserted the cylinder into the hole in the breech leaving space between that and the barrel to keep the seal seated. The hole for the theaded screw was lined up when the exhaust valve back plate rested against the sear and then it was a matter of screwing in the thread and the brass collar over that, then placing the square bolt in it's space in the breech i screwed the grub screw pushing the compression cylinder nice and tight against the under side of the barrel and sealing the transfer port. Now with the cylinder in place i reattached the stock with the crosshead screw in through the front of the trigger guard and into the brass collar on the breech, i was left with four small O rings which were two bolt seals each in .177 and .22.

 Taking the pump rod unit i removed the pump head seal by working it side to side and pulling, it was a black delrin type material with a flat face slightly raised around the outside with a pin size hole in the center and pretty worn all round. The replacment was of the same material but was orange, it had a flat face with a parachute design around the outside which i imagine would leave a little more compressed air before the inlet valve. It was hard to press it into the pump rod unit by hand, so i placed it face down on a clean flat surface  and tapped the pump rod unit with a rubber mallet till it fitted in place. I smeared three or four drops of Abbey SM50 arond the pump head seal and pushed the unit up the compression cylinder, and put every thing back together by reversing all i did to when i took it apart making sure to oil the hinges and grease the pins as i did it

Sharp Innova restored to working order
I gave the innova four even pumps which became increasingly harder, but were still little effort by the forth pump locking and unlocking smoothly at the end of each stroke. I loaded a .22 RWS Superdome into the breech, which for its size and with a 4x32 scope mounted on medium Hawke mounts is surprisingly easy to do and squeezed the trigger. Luckily the pressure of the bolt sping pressing the bolt  against the bolt catch kept the catch in place, but this is not at all reliable and needs sorting. The rifle fired with a low to medium crack and the pellet hit the target board from 27 meters with a hard and loud whack, much louder than one from my .22 HW35 or .22 BSA Mercury sounds at the same distance.

 I can confidently say that this rifle certainly has the minerals, it just needs the missing parts replacing, and some thing done about the chipped off piece at the back of the reciever. I'm sure i can make these parts myself or at least the bits i've mentioned so far, because it also appears all the parts for the trigger adjustment are missing and i have no idea what they look like. Anyway these are things to do next and will without doubt become future blogs, and i'll be sure to take more photo's in future so it'll be easier to understand.


Wing Commander Sir Nigel Tetlington-Smythe  


  1. I hope it helps people, i just wish i could have saved the photo's of the valve internals. Oh well such is life.

    1. hi do you have the sizes for the o rings please

    2. hi do you have the sizes for the o rings please

    3. I'm afraid i don't have the sizes for the O rings and i no longer own this air rifle so i can't measure them for you, However i bought a metric 255 piece O ring set of E bay for around £7 (UK) and have used that on pretty much all replacements for Piston seals, breach seals, and valves, about the only one they don't cover are the small fat O rings that seal the firing pin on the valves. Hope this helps. ATB

  2. Do you have any information on Sharp Ace, my gun needs new seals and exhaust spring, any information?

  3. Do you have any information on Sharp Ace, my gun needs new seals and exhaust spring, any information?

  4. Both the Ace and the Innova use the same seal kit and springs in their valves as the valves used are the same, the housing around the firing pin and return spring is different. An exploded diagram and parts numbers of both rifles can be foung at C W Chambers gun spares ,from these diagrams you can see that a lot of parts numbers correspond on both rifles. Though you can get the spares you need from Chambers, i used T R Robb for my spares as they tended to be a little cheaper Good luck and ATB

  5. So pleased to read this! I bought an Innova in London back in '84 or '85 and used it with good effect on rabbits in Wales. Shortly after I moved to Canada (I have a license so there was no difficulty with the Canadian 500fps limit) and was able to indulge myself in bigger bangs. But I recently resurrected the Innova for some rats in the garden, and it still works, much to the rats' regret. Still stunningly accurate too. But some maintenance must be overdue after thirty plus years and I have ordered a seal kit from John Knibbs, along with a replacement pump head. I hope to be able to follow your instructions in this and in your later posts when these parts arrive. Can you imagine it? - a thirty year old Innova with a Photon XT on top still despatching rats after all these years!

  6. Try to keep the original pump head seal if you can, as they sit snuggly against the outer face of the air inlet valve. the replacements made from nylon are of a parachute design and leave waste air, the ali ones with O ring seals are perfect apart from the fact that you need to cut a half inch thread for it to fit.

    However i don't think the rats care either way.

  7. Good day wing commander
    Thanks for a great read about the inova..
    Ive just aquired myself one in an unmolested condition and very much looking forward to resealing it and getting it back up and running.
    Will be using this as a guide with the exploaded diagram
    Thanks again

  8. I fount the Webley rebel here in the US , possibly last 2 , one .177 and one in .22 both slightly shooting over 12 ft lbs energy , kinda my closet queens here lol :)

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