Thursday, 10 September 2015

.22 Mk l Sharp Innova. A Restoration Project.


I've been doing this blog for about three years now and admittedly, not a lot has been going on for the last few months if the truth be told. The usual reasons really; work, family and being a bit of a lazy git. Anyway, the other day I got an email off a chap who has read my blog entries on the Sharp Innova and asked if I could restore his for him, to which of course I said yes as us airgunners tend to help each other out if we can. We exchanged many emails back and forth and several weeks later, Parcel Force delivers the gun - minus the stock - to the door.


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.22 Sharp Innova, Whisper Silencer. Rhino blocks, and a Tasco 3-9x50 scope.

The Innova on first inspection appears to pump up and hold air just fine, however on dry firing, if the trigger is released slowly there is a slow release of air then the rest is dumped through the valve. So the first order of the day is to strip her down and get the valve apart to get a look at the trigger and sear. I have O rings I can use until the proper kit arrives from T R Robb, but it would be handy to see if anything else has buggered up in there and needs ordering as well. Externally, the rifle is in a really tidy condition and it's owner has had it for the last 30 odd years from new, so it sounds about right that the O ring seals would be starting to perish by now.


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The piece in the middle is all i need.

And this is what arrived in a long cardboard box, wrapped in a metric fuck ton of cellophane. Considering the breech and outer barrel are plastic, there is some weight to it!
I removed the pump arm pin by sliding the circlip out of the way, then pushing out the pin.

The circlip needs to removed with great care as they are a bugger to find if they go pinging off somewhere

Next I removed the roll pin that holds the front end sight unit on, making it possible to remove the front unit that holds inner and outer barrel and the cylinder. 

Roll pin is pretty firmly held in place, but a punch does the trick. Note the pellet tin in the backdround for keeping small bits from getting lost, very important.

To remove the pin that holds the pump arm to the end of the pump rod, simply line it up with the pump arm pin hole at the front end of the cylinder and push it out. You have to tilt the pump rod slightly for the pin to come out.

 The hole for the front end of the pump arm is drilled below centre, so the pin for the swing arm and pump rod sit above this and don't fall out.

The whole pump rod assembly will now come out with the help of a screwdriver, the whole thing was slathered in thick black grease which was not right at all. 

There should not be any grease on a multi pump , just a couple of drops of moly oil here and there.

There was so much that if it was on a main spring on a break barrel air rifle it would have most likely knocked four ft/lb of power off it! You only need three drops of moly based oil now and again to keep the pump arm lubricated. This was going to be interesting! When I got the valve unit apart, it took a lot of kitchen towel to remove the gunk, it got everywhere.

I later recycled this grease for the bearings on the back wheel of my bike.

Remove the brass collar then unscrew the stud to loosen the cylinder with valve inside it.


There is also a trigger adjustment screw that pushed the trigger away from the underside of the breech block, it's missing, just like every other Innova i've come across.

The cylinder came out of the breech easily by sliding the cylinder spacer out by it's little lip, then sliding the tube out, being careful of the transfer port O ring on the top side.

The transfer port O ring seal sits atop the cylinder, removing the spacer lets it come in and out without catching on anything.

This one did not have the nut and screw that presses the tube up into the breech hole like the last one I had did, but seemed to be a really snug fit with the spacer in place regardless. The exhaust valve back guide on the back end of the cylinder unscrewed by thumb pressure alone ...

Looks like you could get or make up a little tool to remove the back guide,  but they tend to move if you use your thumb.

... then out came the spacer, bumper, bumper plate and exhaust valve spring. The exhaust valve came out by unscrewing the brass collar, then removing the screw under this that secures the valve to the correct part at the rear or the cylinder, which has already been done.


I pushed the valve unit out with a piece of dowl; if the pump arm is connected, draw the arm back securing the valve in place with a drill bit then remove the drill bit and pump the arm slowly. The valve will slide out under pressure, but remember to catch the firing pin as this tends to shoot out and get lost somewhere in my experience.

Bumpers, spacers and springs keeps the firing pin in check when fired, I have known many Innova's with the bumper and plate missing. Easy to bodge up and replace if push comes to shove.

I unscrewed the firing pin housing from the valve body by holding one part in a vice and unscrewing it with the help of a wrench, it was on bloody tight but shifted in the end. It only needs to be firmly hand tight as the O ring between the two holds the air pressure in. Again, it was pretty much packed full of grease.

I removed the valve spring and inlet valve ball, then unscrewed the inlet seal stopper. I left the inlet seal in for now as it seemed fine and I was just concerned with cleaning out the grease. 

Grease inside the exhaust valve. Inlet seal and stopper are still inside the body, you'll see them in a later blog when i fit the new seal kit.

When it came to cleaning out the firing pin housing, once the pin was removed I found it was missing the exhaust valve seal and seal washer. It would appear that the only thing holding what air pressure it did hold was the copious amonts of grease. I was going to have to get a washer made up as there was none in stock on any of the spares sites.

The O rings are old ones I had in a tin, so where is the the O ring and brass washer to support it?

A couple of hours later, I was checking to see how far the firing pin went into the housing to see if an old O ring would do the job, when I noticed the pin wasn't quite reaching the O ring. I gave the firing pin housing an extra clean up and noticed that the O ring washer was actually wedged into the housing (that was a relief!), but that the O ring seal was missing, which would explain a lot.

I found the washer wedged in there, the O ring is one I took off an old Innova I worked on ages ago. Needless to say it was buggered.


Seeing as I had to wait for the O ring kit to arrive before I could sort the valve out, I thought I would check out the trigger and sear. I had noticed the trigger adjustment screw was missing which is pretty common in my experience. Tapped out the trigger pin and removed the trigger, out came the sear and the sear spring but no sear liner.

The sear goes the other way up and the spring pushes the rear liner back after each shot, where is the sear liner? I reckon I could knock up a new liner out of a bit of thin flat bar and a tiny grub screw to see if there is any improvement.

The sear sits in it's space in the bottom of the breech unit. The spring sits in it's hole in the sear and pushes against the liner, which moves up the sear when the trigger is pressed. A hole in the liner lines up with a hole in the sear allowing the firing pin to be released. At least that has been the case on the other Innova's i've worked on!

In this case, the sear is upside down with the spring between it and the roof of the sear space, in the breech, the trigger is pushing the sear up until the firing pin can shoot through the hole, allowing air out the valve and on it's journey through the transfer port. In theory this should work fine and hopefully is not the reason for the slow escape of air when the trigger is pressed gently.  If it is, I can fabricate a makeshift liner and if that sorts it I can then order the part. I will just have to play the waiting game for now.

There's refitting the seals, sorting out a sear liner and adjusting the air let off valve on the pump head to come, so that's another couple of blogs in the works.

TTFN

All the best, Wing Commander Sir Nigel Tetlington-Smythe 


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