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Thread: A few questions about pistons and tuning?

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  1. 19-06-2018, 06:18 AM #1
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    never messed with piston weights as I don't have a lathe.

    Rear piston bearings I don't mirror polish. I just use finish emery that still shows sanding marks. The marks will retain lube and I use moly paste on the rear bearing.

    Seal, sized so it can be gently pushed down with one finger for me. Again, moly paste rubbed in the sides but wiped off. The sanding marks retain enough lube.
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  2. 20-06-2018, 05:53 PM #2
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    Quote Originally Posted by robs5230 View Post
    never messed with piston weights as I don't have a lathe.

    Rear piston bearings I don't mirror polish. I just use finish emery that still shows sanding marks. The marks will retain lube and I use moly paste on the rear bearing.

    Seal, sized so it can be gently pushed down with one finger for me. Again, moly paste rubbed in the sides but wiped off. The sanding marks retain enough lube.
    What's your method of seal sizing Rob?

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in
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  3. 20-06-2018, 07:31 PM #3
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    Quote Originally Posted by look no hands View Post
    What's your method of seal sizing Rob?

    Pete
    Crude but simple. I have no lathe so spin the piston up at slow speed in a drill. Emery applied at the same angle as the seal side and gentle pressure. Any more than that or if spun faster you stand a chance of overheating / melting the side of the seal.
    Just a matter of trial and error and hopefully not going to far. Never ruined one yet though.
    I try to be very careful around the leading / front / sealing edge.
    I've found it best with a spare pair of hands to hold the drill as I'd rather not clamp tools in a vice.
    Once the seal is down to the right size (able to slide down with a gentle push) I apply a smear of moly paste to the sides of the seal and wipe off. A small amount of lube is retained in the sanding marks.
    I've found the custom air seals very difficult to size as I've found them to be a loose fit on all the pistons so stopped using them and instead stick to O.E. seals.

    I use the same method to polish rear bearings on pistons and also to the Diana piston area where the crimps "cloverleaf " it.
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  4. 20-06-2018, 08:15 PM #4
    look no hands's Avatar
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    Quote Originally Posted by robs5230 View Post
    Crude but simple. I have no lathe so spin the piston up at slow speed in a drill. Emery applied at the same angle as the seal side and gentle pressure. Any more than that or if spun faster you stand a chance of overheating / melting the side of the seal.
    Just a matter of trial and error and hopefully not going to far. Never ruined one yet though.
    I try to be very careful around the leading / front / sealing edge.
    I've found it best with a spare pair of hands to hold the drill as I'd rather not clamp tools in a vice.
    Once the seal is down to the right size (able to slide down with a gentle push) I apply a smear of moly paste to the sides of the seal and wipe off. A small amount of lube is retained in the sanding marks.
    I've found the custom air seals very difficult to size as I've found them to be a loose fit on all the pistons so stopped using them and instead stick to O.E. seals.

    I use the same method to polish rear bearings on pistons and also to the Diana piston area where the crimps "cloverleaf " it.
    I've just put one the new Oz seals on my Brocock Indy (Basically a Gamo action), it's the seal that covers the whole dovetail and reduces the lost volume, seem to fit pretty well but the normal type seal they do does seem a bot loose, I didn't size that one as I think I'll just shoot that one in, it'll be interesting to see what the Maccari seal is like as I've never had one of those before.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in
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  5. 20-06-2018, 08:52 PM #5
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    Quote Originally Posted by look no hands View Post
    I've just put one the new Oz seals on my Brocock Indy (Basically a Gamo action), it's the seal that covers the whole dovetail and reduces the lost volume, seem to fit pretty well but the normal type seal they do does seem a bot loose, I didn't size that one as I think I'll just shoot that one in, it'll be interesting to see what the Maccari seal is like as I've never had one of those before.

    Pete
    I only size if they need sizing. My last oz seal honked like a goose it was that tight and was a pig to size so I binned it.
    I did buy one of their gamo closed faced seals for the same reason you stated above but never got round to fitting it on the TX as it shot so well with a sized O.E. seal
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