Prosport piston

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Neknadroj
Posts: 4
Joined: Mon Jul 23, 2018 10:13 pm

Prosport piston

Fri Jul 27, 2018 5:07 pm

Hi newbie here
I am after some technical info
I have just purchased a 4 year old prosport and I have had some troubles fitting a Tim bum kit
My question is how deep is the piston with the top hat and any packing removed
I am not sure if there is something stuck at the bottom of the piston were the spring and top hat fit
Tuning kit spring guide and top hat seem too long even with no packing (that I can see)
Banged he’ll out off it to see if anything else is in there but nothing coming out? Spring guide would need cutting down by about 6mm for it to seat on the back of the piston rim
Many thanks for any help.
Cheers

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pelletcaster
Posts: 71
Joined: Mon Feb 16, 2015 10:07 pm

Re: Prosport piston

Fri Jul 27, 2018 7:24 pm

Never had a Prosport - too sad but still on my wish list anyway.

So I just can give you the inside depth of my TX200 HC - 110 mm.

From fettling LGV/LGU I know that washers/tophats can sit quite persistently inside the piston due to old grease.
Put the piston head down and fill some grease dissolving liquid like break cleaner and leave it overnight. Repeat the wash the next day and hammer the piston stem forward down on a wooden surface. Repeat if necessary. Anything left/stuck inside should come out now easily.

Hope this helps.
Live is a journey - not a destination.
-----------------------------------------
AA TX200 HC / LGU Master / LGV-CU / HW35 / HW50s (1974) / HW50S (2015) / HW90 / DIANA 34 T01
DS MK4iS-S / SPA P-12 / CZ200S-Green

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Timmytree
Posts: 927
Joined: Sun Feb 15, 2015 11:50 am

Re: Prosport piston

Sat Jul 28, 2018 3:20 pm

It may have a washer inside the piston, as above, try brake cleaner, use one of those extending magnetic wands down the side of the latchrod, you can then gently wiggle any washers out with a circular movement.

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Neknadroj
Posts: 4
Joined: Mon Jul 23, 2018 10:13 pm

Re: Prosport piston

Sat Jul 28, 2018 3:23 pm

Hi
Thanks so much for the reply
That confirms my problem I can only measure 97mm to the bottom of the internal piston.
And thanks for the great idea for removing the offending packing, I will give it a go.
Cheers
All the very best
Ken

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FPoole
Posts: 305
Joined: Mon Feb 16, 2015 2:37 am

Re: Prosport piston

Sat Jul 28, 2018 6:46 pm

Fill the piston with brake clean or mineral spirits and let it sit for a while. I use a thin stiff piece of wire to slip down beside the latch rod and try to get the weight moving. I then use a block of wood to bang the piston stem down on. Usually gets the job done.

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Neknadroj
Posts: 4
Joined: Mon Jul 23, 2018 10:13 pm

Re: Prosport piston

Sat Jul 28, 2018 9:40 pm

Hi
thanks for all the help. I have now sorted the problem
I think someone in the past has forced a very tight fitting washer. That was never ment to be in the piston down to the end of the cylinder. At first I tried the brake cleaner and alcohol but noting was going to shift it. So I removed the piston shaft from the piston this gave me a view from the seal end
Now I could get a thin screwdriver on the edge of the washer. It was about 4mm from the bottom of the piston
A quick tap on the end of the screwdriver flipped the washer horizontally in the piston tube. Now with the ade of a pair of very long nose pliers I got the washer out
As a double check I re measured the piston depth. Just as I was informed the depth was 110mm. A good clean and piston shaft Relocktighted in place and the Tim Bum tune kit fitted like a glove. The cocking now feels great. I fitted the two supplied preload washer after a quick chrono to get 10.7 Foot pounds. I will let the gun bed in a bit befor any outhe plus or minus pre loading
Thanks again for all your help.
All the best
Ken

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