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andrewsofia

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Hi All,
Recently picked up a pro mac 800 saw that unfortunately is missing a decomp valve.

Looking for knowledge of any other saws valves that might work or if could plug with bolt and still run?

What size is thread for bolt replacement.
 
Hi All,
Recently picked up a pro mac 800 saw that unfortunately is missing a decomp valve.

Looking for knowledge of any other saws valves that might work or if could plug with bolt and still run?

What size is thread for bolt replacement.
Could you show a couple of more pictures? Pm800 are all yellow and had Q port exhaust without the decomp.
 
The DSP for an 800 is unique to the 800, 805, DE80 and the Super 850. It will also fit an 8200 but no port had been drilled in the 8200. The DSP is desirable but not necessary as both the early 800 and the 8200 were not drilled. I believe the correct pitch is 3/8” coarse, Make sure to use a washer and a short bolt so you won’t bottom out and break something.

Ron
 
The DSP for an 800 is unique to the 800, 805, DE80 and the Super 850. It will also fit an 8200 but no port had been drilled in the 8200. The DSP is desirable but not necessary as both the early 800 and the 8200 were not drilled. I believe the correct pitch is 3/8” coarse, Make sure to use a washer and a short bolt so you won’t bottom out and break something.

Ron
Rwoods, do you know if it is a straight or NPT tapered hole? i found a few 3/8 plugs but most are tapered
 
The DSP for an 800 is unique to the 800, 805, DE80 and the Super 850. It will also fit an 8200 but no port had been drilled in the 8200. The DSP is desirable but not necessary as both the early 800 and the 8200 were not drilled. I believe the correct pitch is 3/8” coarse, Make sure to use a washer and a short bolt so you won’t bottom out and break something.

Ron
Rwoods, do you know if it is a straight or NPT tapered hole? i found a few 3/8 plugs but most are tapered
The DSP for an 800 is unique to the 800, 805, DE80 and the Super 850. It will also fit an 8200 but no port had been drilled in the 8200. The DSP is desirable but not necessary as both the early 800 and the 8200 were not drilled. I believe the correct pitch is 3/8” coarse, Make sure to use a washer and a short bolt so you won’t bottom out and break something.

Ron
would something like this work:

https://www.ebay.com.au/itm/264786015942
https://www.ebay.com.au/itm/401478515752
 
3/8-16, straight threads. Don't mess around with anything else.

If the cylinder has the port bored for the compression release you will risk having carbon accumulate in the hole and come loose. I have a couple of similar units - both were Double Eagle 80's - that died from plugged compression release ports dropping prediamonds into the combustion chamber.

There were some PM800's built with the compression release and some without the compression release and the "Q port" in the exhaust to relieve some compression for starting.

Mark
 
3/8-16, straight threads. Don't mess around with anything else.

If the cylinder has the port bored for the compression release you will risk having carbon accumulate in the hole and come loose. I have a couple of similar units - both were Double Eagle 80's - that died from plugged compression release ports dropping prediamonds into the combustion chamber.

There were some PM800's built with the compression release and some without the compression release and the "Q port" in the exhaust to relieve some compression for starting.

Mark
Can you scrape and vacuum the port out ? Or if its not drilled just bolt and go.
 
Missed your location - in the US it is 3/8" NC not a pipe thread. Your picture shows that your saw has a port drilled so it is best you find a valve. They are hard to find but easy to spot - due respectively to scarcity and unique coarse threads. If you cannot find one and you intend to use the saw personally, I might be able to part with one of mine.

Ron
 

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