If/When you come into some cash buy yourself a APS UAR
Best spring tester out there, fastest spring change I know under 30 secs
(did have 10% off last week like a lot of stuff at TWG)
I have got about half a dozen or so springs tested with a bit paper wrapped/stuck on them
tested the fps both ways if irregular type so got a rough idea of what is what from hot guns
Any hot/warm gun I can pull the spring out & test in UAR then select another 15-20 fps less
Takes a bit of guesswork out of it all and does work fairly accurately considering
I say fairly accurately coz if you improve seals, correct AoE, spring guides, spacers ShortStroke etc...
Well it will through up other factors into the mix of course blah x 3
I don't normally cut springs - only time I've bothered to cut a spring is cutting off ye old hook bit
A new m100 or M105 is only about £7 in the end
I'll tend to use the warmer springs in say 300mm guns or less and SS a tooth maybe if needed
I tend to reject springs that are too short say less than 150mm
normally a v2 box is about 160mm aprox in length - if spring is shorter than box I'll tend to bin it
Mainly coz I feel really short springs have less tension as piston releases and doesn't slow piston much
I feel that a light shorter spring having less tension in early stages of retraction contributes to overspin more
(probably no way as bad as I assume but that is just me being a tart)
In general I aim for about a 160mm to 170mm spring length not less but that is just me being a tart
Some springs can be a tiny bit tight fir over the spring guide or inside piston blah x 3
If in doubt just buy a new spring of better material than some cheapo china guns
They don't cost the earth in the end but a UAR is great little gimmick for testing springs with
If the sector gear is shimmed high, so there are fewer shims on the top of the gear, then it'll pinch the tappet plate between the top shell and the sector gear.
This can lock a box. The tappet plate should be free to move and return without resistance. And this needs to be true for all positions of the sector gear. If the sector gear has any blemishes and dings on the outer race then it can grab.
When I shim my v3 I have to work with that space in mind. And it often means the sector gear runs off centre a little on the piston body (running low in the box). And I have to accommodate that by running the rest of the gears slightly off perfect. Fortunately the v3 box can cope with this and there is enough movement to be able to get a decent mesh on the pinion even if you need to move the gears slightly.
This could also be caused by the tappet plate/sector gear shimming.
I'd go back to the gearbox and start from scratch.
Start with the sector gear by itself. Get the shimming perfect, then drop in the tappet plate and work out exactly how many shims need to be up top for it to run free. Write that down.
Then start the regular shimming process from the bevel gear through to the spur gear. Shim the sector gear like normal to the spur gear, but make a note of how many shims are in what position on the sector gear.
You need to do this because I can guarantee the shimming done properly has put too few shims on the top of the sector gear. Do the math and work out how many shims need to move on the other 2 gears to be perfect on the sector with the best tappet plate gap.
Make the shimming adjustments then check the motor, You should find it'll engage just fine, but it has to be wound in another half turn.
If they're gunked up maybe get some rubbing alcohol (or failing that just some surface cleaner) and press a piece of kitchen towel into the threads then twist. Keep doing until the kitchen towel stops picking up black. Otherwise you're basically going to be rubbing metal shavings etc. into the threads every time you remove it, which isn't good. If you want a good, semi-permanent lube then copper grease is great for this sort of thing and won't dissipate like silicone.