bsa mercury

[dave23]

just replaced spring and piston seal on a old mercury,now the trigger block don't line up.
can any one tell me what ive done wrong.?

[Shed tuner]

just replaced spring and piston seal on a old mercury,now the trigger block don't line up.
can any one tell me what ive done wrong.?

nothin you've done wrong... but take a look at the back block (when removed)... the threaded bit is secured to the actual block with an internal nut, so it can be indexed. It's probably come loose and allowed the threaded section to rotate, buggering up the indexing.

Tighten than nut (a bit, not fully), screw the block in, make a note of how many degrees of rotational adjustment you need, take it apart, adjust. Repeat as necesary. Mark it to guard against unplanned movement during test fitting. There should be a "gripping washer" like a aggressive star washer, but bigger, between the threaded section and the actual block. Once you are certain on alignment, that threaded section can be threadlocked in place to the block.

[piggy589]

How far out in degrees,has the threaded portion of the back block moved?

[dave23]

How far out in degrees,has the threaded portion of the back block moved?

about 45degrees out

[ggggr]

just replaced spring and piston seal on a old mercury,now the trigger block don't line up.
can any one tell me what ive done wrong.?

Proper fix--Adjust the nut.

other fix (if it is at say 4 o clock rather than 8 o clock) , take a file gently to the back of the cylinder until the block goes to about 5 o clock and then nip up.

If it is at 8 o clock, a bit of twine between the 2 "may" do the trick.

[MartynB]

Proper fix--Adjust the nut

As above, years ago I thought it would be a good idea to take back block completely to pieces, I did get it aligned but it took ages with adjusting, scrrewing on testing, repeating etc

Never took one apart again

[look no hands]

I honestly wouldn't worry about it, a few of mine have a small gap between the back block and cylinder, as long as the trigger guard part is lined up with the stock cut out and cocking slot, then there shouldn't be a problem.

Pete

[Weasle]

nothin you've done wrong... but take a look at the back block (when removed)... the threaded bit is secured to the actual block with an internal nut, so it can be indexed. It's probably come loose and allowed the threaded section to rotate, buggering up the indexing.

Tighten than nut (a bit, not fully), screw the block in, make a note of how many degrees of rotational adjustment you need, take it apart, adjust. Repeat as necesary. Mark it to guard against unplanned movement during test fitting. There should be a "gripping washer" like a aggressive star washer, but bigger, between the threaded section and the actual block. Once you are certain on alignment, that threaded section can be threadlocked in place to the block.

I've got 2 that I'm restoring with the same issue...I'd heard of both methods.

I've just got to select the route of least risk.....however I've been tying to make up my mind for approx. 6 months.......( ;-)>

Cheers Steve

[look no hands]

I've got 2 that I'm restoring with the same issue...I'd heard of both methods.

I've just got to select the route of least risk.....however I've been tying to make up my mind for approx. 6 months.......( ;-)>

Cheers Steve

You just need to remember that once that nut has been undone that you need to make sure that it's threadlocked as if it's done up and it comes loose you'll struggle to get it back undone as the back block will just spin and not come undone, I had that problem with a Challenger.

Pete

[Weasle]

You just need to remember that once that nut has been undone that you need to make sure that it's threadlocked as if it's done up and it comes loose you'll struggle to get it back undone as the back block will just spin and not come undone, I had that problem with a Challenger.

Pete

I think that gives me my option...take a file to the cylinder...carefully.
Cheers Steve

[Shed tuner]

I think that gives me my option...take a file to the cylinder...carefully.
Cheers Steve

If not fixing it properly, I'd go with a wrap of copper wire to space it out instead.. much easier/quicker, the wire will conform / squash and bite nicely, it can be fine tuned with different thicknesses, and it's reversible. As a bonus you also gain a fraction of a mm more stroke

[Weasle]

If not fixing it properly, I'd go with a wrap of copper wire to space it out instead.. much easier/quicker, the wire will conform / squash and bite nicely, it can be fine tuned with different thicknesses, and it's reversible. As a bonus you also gain a fraction of a mm more stroke

Many thanks John.

As and Engineer....I think I should attempt to do it Properly......watch this space.

Has any one got a knackered one that I could us as a trial / development unit ?

Cheers Steve

[Steve Zodiac]

Can’t you just fit the removed threaded collar to the trigger block and mark with point where it needs to be nipped up to after a trial fit , then do the same on the nut side ?

[Weasle]

Can’t you just fit the removed threaded collar to the trigger block and mark with point where it needs to be nipped up to after a trial fit , then do the same on the nut side ?

That's going to be the plan...

[Weasle]

After many months, today I reassemble my 2 early '70's Mercury's.

I replace both of the nylon heads with Ali ones, used the old springs - they were both straight as die - replace the spring guides with Acetal ones and added top hats.

I managed to fit the back block without a compressor - what a faf - and I spaced out the back block to get it in the right angular position.

The bolt holding the front stock mounting bracket to the cylinder of one had to be drilled out and re-tapped

One is showing 10.5 and the other 11.0 over the Scan using 5.5 Super Domes, after about a couple of dozen pellets thru them.

I've got an early BSA lightning lined up next.....hopefully that will be a simpler task?

Give me an HW or an AA to rebuild any day.

Cheers Steve