I'm rebuilding my crosman 766 again...

[bustachip]

and I have a couple of questions for those in the "know". One, does the valve dump all the air "completely"
with one 10 pump shot, or will there be a little air left in the valve? Two, if so what do guys do to fix it, use
a stronger hammer spring or a lighter valve spring?

And three, in this parts diagram it shows a (#2200-037 breech sleeve) going in the valve first, then the
(#130-036 breech gasket) goes in on top. Is the (#2200-037 breech sleeve) needed, or do you guys just
use the (#130-036 breech gasket)? Reason I'm asking is, I don't remember my 766 having a (#2200-037
breech sleeve), but I ordered one anyway and it doesn't seem to fit like I think it's supposed too...lol. The
pic in the diagram doesn't really show how it's oriented?



Here's couple of pics of the part I received (#2200-037 breech sleeve)?




If anybody has any answers about this part, or the valve dumping all the air, I would appreciate it.
Thanks guys, TMurray 

[longhunter]

The breech sleeve is orientated like in the second photo. The "cylinder" part of the sleeve goes inside the breech seal, and the metal "washer" side goes against the valve port. Make sure that the transfer port is properly lined up with the corresponding hole in the comp tube, or it'll leak air, when fired. It can be tweaked after the valve is in the tube. I use the back end of a proper sized drill bit. Just stick the bit in the transfer port hole, and gently move the port side to side, until it lines up.
The gun should dump 10  pumps. If it doesn't, use a lighter valve spring, versus a heavier hammer spring. Less wear and tear on the gun.

[unionrdr]

PT# 037 is the front main valve body section. That port must be squarely aligned with the breech port hole as he said. The cut tube/metal breech gasket goes between them when all is oriented properly to bolt together. And 030 takes the place of the old metal cocking piston on the other end of the hammer spring. I used the upgraded hammer spring in my 160, as the original powder blue painted one looked a lil weak and squished a bit shorter from the bolt being closed all that time? Nice, crisp little double click when I pull the bolt back and cock it.

[bustachip]

The "cylinder" part of the sleeve goes inside the breech seal, and the metal "washer" side goes against the valve port.

First off, thanks for the replies guys.

As the quote up top says, this is how I was trying it as it only made sense to me that way, here's a pic of my
valve with the breech gasket installed....


Problem is, in my mind, the breech sleeve should go inside of the port hole on #766-112 barrel support,
otherwise whats the point of the breech sleeve to start with...lol. But that ain't happening because the port
hole diameter is .125" and the O.D. of the breech sleeve is .152", so without drilling the port hole larger
the breech sleeve just butts up against the port hole, which isn't any good. Right now I just have the breech gasket installed in the valve.

Also, over on the "Crosman Green Forum" I got a reply with this diagram that says you don't have to use the breech sleeve, lower left circled in red.....

 
I know this is a newer diagram but it's probably still applicable.   

My 766 will dump probably 90 to 95% of the air in the valve with 10 pumps, so I guess I'd have to find a
weaker valve spring, would you guys happen to know where I could find one that would work...lol??
I have an extra one, wonder if I could clip a coil or two to fix it?

Thanks for your help.
TMurray

[longhunter]

What the sleeve does is keep the seal from blowing out, from the high pressure blast of air. I'd still use it, if it were mine.
As far as a weaker spring, take the factory one to the hardware store, and match it up with one that is the same outside diameter, and length, roughly the same number of coils, and made with thinner wire.

[Tack Driver 10]

There are 3 versions of the 766.
The V1 combines the breech and valve. (no breech seal)
The V2 has the brass sleeve and seal.
The V3 just has the seal.

You should determine which version you have.
Since you stated you didn't recall the brass sleeve in your gun
I would think your gun is a V3.
What's the serial number?

https://support.crosman.com/hc/en-us/search?utf8=%E2%9C%93&category=200223634&query=766&commit=Search

Either way I would leave it out as it can seriously restricts power.

I have a jazzed up 2100 and it dumps 15 pumps at 900 FPS.
I used a lighter valve spring and a heavier hammer spring.

[bustachip]

What the sleeve does is keep the seal from blowing out, from the high pressure blast of air. I'd still use it, if it were mine.
As far as a weaker spring, take the factory one to the hardware store, and match it up with one that is the same outside diameter, and length, roughly the same number of coils, and made with thinner wire.

Well, if I were to use it I will have to drill the "barrel support" port hole at least .100" otherwise it's just pushing against the breech sleeve and not getting to the rubber gasket I don't think that's the best scenario. But it could be made to work.

Thanks for the spring info, I'll do some looking around for one.

TMurray

[bustachip]

There are 3 versions of the 766.
The V1 combines the breech and valve. (no breech seal)
The V2 has the brass sleeve and seal.
The V3 just has the seal.

You should determine which version you have.
Since you stated you didn't recall the brass sleeve in your gun
I would think your gun is a V3.
What's the serial number?

https://support.crosman.com/hc/en-us/search?utf8=%E2%9C%93&category=200223634&query=766&commit=Search

Either way I would leave it out as it can seriously restricts power.

I have a jazzed up 2100 and it dumps 15 pumps at 900 FPS.
I used a lighter valve spring and a heavier hammer spring.

900 fps....that thing is humming..lol. I chronied mine today with 7.33 jsb it avg 669 fps with 10 pumps and
whatever air is left in the valve.

My 766 is a phase II model with the tapered steel barrel shroud, model # starts with 1179 so it was
manufactured in November of 1979. I guess I'll be going back inside again...lol, I can put it together blind
folded now .
I just finished rebluing all the metal and screws, trigger blade...etc


Is your 2100 a 177cal, and what pellet are you shooting to get 900fps, and any mods to the valve?

TMurray

[Tack Driver 10]

The 766 V2 with the tapered barrel shroud is my favorite.
That bluing looks really nice. What product did you use?

My 2100 is .177 cal and all the tests were done with 7.9 CPHPs

An adjustable piston, valve mods and sealing the leaks are the major mods.

Lots of 2100/2200 (766) mods so here's a few links that spell it out.

https://www.gatewaytoairguns.org/GTA/index.php?topic=136879.msg1369809#msg1369809

https://www.gatewaytoairguns.org/GTA/index.php?topic=136474.msg1364572#msg1364572

One piece breech:
https://www.gatewaytoairguns.org/GTA/index.php?topic=132874.msg1347720#msg1347720

[bustachip]

Awesome work man..thanks for sharing, I guess there's more to do to my old 766...LOL My barrel shroud
had light rust and minor pitting in spots, I stripped it with 200 then 400 then 0000 steel wool, and minor
filing.






I used brownells Dicropan T-4 "first",I applied 4 coats with 0000 steel wool in between coats, then lightly steel wooled with Remoil. A day later I applied 3 coats of Perma blue with 0000 steel wool in between coats, I did this to all the metal parts.
(these 2 pics were before I added the 3 additional coats of Perma blue, just using the Dicropan T-4 they were
much more black rather than blue).



Anyway, my brass valve stem blew the old white seal it had, so I found a o-ring to fit in there and that
is what is currently sealing it. What do you recommend for a good valve stem replacement. Did you buy
or make your own, I have delrin and a lathe...lol, but no mill. I see some delrin looking valve stems on
ebay?

Thanks, TMurray

[Tack Driver 10]

Thanks for the tips on bluing.

The best valve stem to use on a high power gun is the MRod valve stem.

It's designed to take 3K psi and made from what looks like Delrin.

P/N 1700-140, $1.68 a copy from Crosman.

I usually get several at that price.

[bustachip]

Thanks for the tips on bluing.

The best valve stem to use on a high power gun is the MRod valve stem.

It's designed to take 3K psi and made from what looks like Delrin.

P/N 1700-140, $1.68 a copy from Crosman.

I usually get several at that price

The stem you're talking about and use in your builds, is the sealing surface just flat and made of delrin,
or does it have some kind of sealing material on the surface, and flat or concave surface?

The valve stems look pretty easy to make from delrin.

Also what kind of results did you get with your o-ring probe mod in your pumpers, before and after?
You've given me a lot to think about...LOL.

TMurray

[Tack Driver 10]

Not sure what difference the probe seal made.
I made several mods at once when the gun was apart.

Here's the valve stems for comparison.
Same as the stock stem but made from Delrin.

[bustachip]

Thanks again Tack Driver 10.

TMurray

[unionrdr]

Not sure what difference the probe seal made.
I made several mods at once when the gun was apart.

Here's the valve stems for comparison.
Same as the stock stem but made from Delrin.

Not exactly the same. Wouldn't work in my Crosmans. The Delrin collar is shorter than the brass one. I polished the brass one and the shaft. Reused it and it's great!

[bustachip]

Not exactly the same. Wouldn't work in my Crosmans. The Delrin collar is shorter than the brass one. I polished the brass one and the shaft. Reused it and it's great!

Thanks uniondr, I've got two stems coming one old brass type and a newer delrin type. Right now I've got a
small o-ring in my brass stem and it's holding at 669 fps, but I don't think it will last (temporary fix).

I'll check them out when they get here, I might make one myself out of delrin, donno yet, if so I can make it
the same as the brass one.

I've got some tinkering to do still.......
TMurray

[unionrdr]

You're welcome. The valve stems are a lil different length too. Keep an eye on that to keep everything function within the set limits.

[bustachip]

I tried a few of Tack Drivers mods today, I decided not to use the breech sleeve and instead I turned the
nipple down on the barrel support and added a .251" brass sleeve for a tighter seal, I made it about .030"
longer so it would for sure be pressing in on the gasket.
Here's a couple of pics.....
(cleaned up nipple)


(.251" sleeve added)


I also added the extra weight on the hammer.....



I made a little longer probe tip....


And the current valve stem "fix" I'm using till I get some new ones this week....


I still haven't found the right springs to try and fix the valve, so it will dump all the air, hopefully I'll come
up with some this week. It's still shooting around 650 fps with jsb 7.33's with 10 pumps, but the bolt wants
to blow back a little, guess it needs some kinda seal in the barrel, or maybe a new bolt and spring?
If I hold the bolt shut when I shoot it, it will shoot over 700 fps with the 7.33's....lol.

So, still a work in progress, but I'm not giving up
TMurray   

[Tack Driver 10]

Looks like it's coming along nicely.

I sealed the probe on my 2100 by cutting the breech end of the barrel
back about .040" and adding an o-ring between the breech and barrel.
Made the probe from brass to fit snug.

Also a pic of the MRod valve stem without the Delrin.

[bustachip]

Thanks for the tips again Tack Driver!

Question....are the probe tips threaded on, or drilled and pinned?

I thought about the o-ring in the breech and cutting the barrel to make up the difference, I also thought
about a o-ring on the probe? I haven't decided yet.

I'm hopeful a heavier hammer spring and or lighter valve spring will fix the valve dumping issue, that and
sealing the barrel from the probe end, "should hook it up".

I'll post back when I get some results.....
TMurray