Gast vacuum pump

[Minnesota Tapper]

Setting up my first vacuum setup and had some questions. I have an oil less gast 1550 I plan to run off a predator motor with a la pierre releaser.
1. What size motor? Id like to size pulleys to run the motor at a moderate rpm while still turning the gast at 1725 rpm.. Will the small 79cc predator have enough power to run a slower rpm if i size up the pulleys to turn the pump faster? or should I go up to the 6 horse motor?

2. How low rpm can I run the motor while turning the gast at 1725? I was thinking equal size pulleys. Or can I go lower yet?
3. My gast didnt come with the glass jar intake filter or exhaust muffler. I will make a muffler somehow to try and get it as quiet as possible. But what about the intake side? Do I need the $100 glass filter for the intake side of the pump? Or is their something else i can use as a filter?

[Sap Raider]

This site is very helpful with the pulley sizing. https://www.blocklayer.com/pulley-belteng.aspx
As far as the speed here is a tachometer that works to get the speed of the engine correct https://www.amazon.com/Searon-Digital-Tachometer-Counter-Snowmobile/dp/B01H5ECBZ0/ref=sr_1_2?dchild=1&gclid=CjwKCAiAirb_BRBNEiwALHlnDz4UX2sobUda5OD4Lwwf N9LP_A5bnoc5RZVn7cY4mKmd8K5A4tPtZhoCLpwQAvD_BwE&hvadid=327375298785&hvdev=c&hvlocphy=9005309&hvnetw=g&hvqmt=e&hvrand=8511448550129893443&hvtargid=kwd-342265240490&hydadcr=5735_9183708&keywords=gas+engine+tachometer&qid=1609462296&sr=8-2&tag=googhydr-20
As far as the jar, a moisture trap will do that for you. I made a similar setup and it work great.

[Minnesota Tapper]

The intake jar isn't necessary to filter debris particles from the air sucking into the pump?

[Sap Raider]

The moisture trap takes care of what the moisture trap is for, moisture trap will let the vapor accumulate and can be drained. There will be no debris that will make it through to the pump.

[MT Pockets Producer]

We run two 1550 set ups on the 79cc predator. The engine has a 4 inch pulley and the pump pulley is 6 inch. We don’t run a tach so I can’t tell you what our engine rpms are but we run them somewhere between 1/4 and 1/2 throttle most of the time. The pump runs less tha 1725 but pulls enough CFMs for our system. They could probably be throttled down a little slower but any little hiccup in the motor would cause it to stall with 26 inches of vacuum pulling against it. Especially if there is the slightest bit of moisture in your fuel. Ours have a 4 1/2 gallon auxiliary tank and when running around the clock we get over 30 hours before needing to fuel. We run moisture traps and do not use the jar. For a muffler we used pipe fittings from the pump exhaust into an end cap glued onto 3 inch pvc pipe which is about 6 or 8 inches long. On the other end of the pipe we glued another cap on and Plumbed an elbow pointing down. The pipe is positioned horizontally so we drill a small hole in the bottom so any moisture drains out.

[Minnesota Tapper]

Great Info! The pulley ratio calculator on that website is very helpful. My 79cc predator is ordered. I'll have to experiment with different pulleys. I want to run it lower rpm but not so low it could quit. Does the pump exhaust not get hot enough to melt the pvc muffler?

Lookimg forward to getting this all set up soon. Is there any specific way to plumb the vacuum to the releaser? I was planning to have a check valve right after the pump, then go to a 15 gallon air tank as a booster. Then to a pvc moisture trap. Then run pvc to the sap releaser. Any problems with this? I see some not using a booster tank and wondering if thats necessary or will cause me issues?

[MT Pockets Producer]

21724We experimented with a few different pulleys and the 4 and 6 inch combination seemed to be the best. The pvc pipe only gets warm, no where near the melting point. A check valve at the pump is a must. We use a a $10 brass swing valve from Home Depot. We are plumbed just as you planned without the booster(balance) tank. We go from Pump check valve to a PVC moisture trap and then the releaser. We use one inch sap line between the pump and moisture trap and the same from the trap to the releaser.