Stihl 075 + 076 decompression valves

[TreeTrucker]

Hello all, I have 2 large Stihl chainsaws that I'm considering refurbishing. My question is about the compression releases. On both the 075 + 076 they screw into the top of the barrel and terminate in a port running to the cylinder bore. This port has a standard machine screw threaded into it that terminates at the cylinder bore. well with the screw in place it blocks off the compression completely, so I don't see how the compression release can work. If the screw is removed the pressure simply exits out the side of the cylinder. The saws are brutes, I've heard of choppers using them without a compression release but thanks ,I think I'll pass on that deal. Any input is mucho appreciated

 

[D'Animal]

The side hole is that goes to the combustion chamber is drilled adn then the out area is threaded and a very short screw is installed to block off the hole.

When/If you remove the decompression valve, you should have a small thin ring that seats the end of the deco valve. The Original ones were Copper and the replacement ones are steel. This gives the Deco Valve a solid seat against the cylinder. If the washer is lost or left out, it will not seat propoerly and compression will blow out. As a "I don't know what I'm Doing" fix, people put a long bolt in the side of the cylinder and it completely blocks off the decompression port all together.

 

[TreeTrucker]

re: stihl o75 decompression valve

D'Animal - Thank You very much for your quick reply. That's exactly the way these 2 saws came to me, (with a long screw in the hole)
One of the 1st things I did when I got these saws was to go down to the hardware store and buy enough allen head metric machine screws in the different lengths to replace all the ones on the saws. Even with a short screw in the hole (can I say that on the air??) , these saws have alot of kick to them. I'll see of I can get them fired up today. Just the thing to let my neighbor listen to after putting up with his FIVE DOGS barking every day !
Oh , and where is the best place to find parts for these 2 saws ? 075AV + 076AV I dont see alot of parts for them even on ebay , and alot of them are used parts.....

 

[D'Animal]

Here are some Original Part Numbers. They may be superseded.

9045 371 0930 The 5 x 8 mm screw in the side of the cylinder
1111 020 9504 Decompression Valve
9636 003 0420 Decompression Valve Seating Washer

The parts are still available from any STIHL Dealer.

Humbolt County is kinda Big so here are a few dealers in your area/county.

Eureka - Western Chain Saw
Fortuna - Wildwood Chain Saw
Garberville - Milts Saw Shop
McKinnleyville - Miller Farms

 

[TreeTrucker]

re: stihl o75 decompression valve

D'animal, thank you again for your quick reply. Although we've never met, you truly must be an amazing person to give so much of your time to helping people. The dead on advice you provide and the sheer volume of it is really incredible. As for my 075 + 076 projects, i'm tackling them one at a time, starting with the 075. I've got the compression release working right, the saw has good compression, (125-150), it's got a strong spark, but it's not getting fuel. So, the carburetor is going to need overhaul. these saws have sat for several years or more , so I would guess they will need a complete rebuild ?

 

[D'Animal]

The fuel filter and fuel line in both saw will probably probably need to be replaced. Start with the filter and work towards the carburetor. you may find a cracked hose or that the fuel filter "spong" has dissolved inside the filter housing. If you rebuild the carburetor, you wil suck all the nasty crap into the carburetor.

Once you get it running, you may have a problem with the crankcase filling with bar oil. This means the "O" rings on the oil pump have dried out. Pretty easy to replace once you know where to look.

 

[TreeTrucker]

re: stihl o75 decompression valve

Okay , thanks I'll proceed in that direction