Lack of vaccum on a gast 1550

[mtbreezefarm]

I have a gast 1550 I have hooked up to a 5.5 hp gas motor. It runs fine but it takes a long time to build vaccum and even then I have yet to get above 10". This is even closing the lines off and building vac in a zero tank. The tank is good, no leaks. I bought the pump from someone saying it was already reversed and it appears to be. I installed new seals on the pump when I assembled it after inspecting the veins and such. Any ideas? I've tried revving the engine all the way up with no change. Any one run into this before?
Thanks

[maple maniac65]

what speed is the pump turning?

[mtbreezefarm]

The idle speed on the motor is 1400 +/- 150 RPM and full throttle at 3,500. I've been running it at half to high idle so somewhere around 2500 rpm maybe.

I have connected the gast to the bas motor using a connector instead of pulleys and a belt so the rpm transfer directly.

[maple maniac65]

are the veins sticking? are they in the correct way? Maybe this pump cannot be run reversed

[mountain man maple]

What model of 1550 is it? Which direction are you spinning vacuum pump? How many taps are you using it on? Is it lubricated or dry vane pump?

[madmapler]

Those pumps run at 1725 rpms but I ran mine on a gas motor a little faster and got 23hgs. without any troubles. They only require 3/4 hp.electric and depending on the model# are designed to spin in one direction or the other. Perhaps the zero tank is the issue. Depending on the size of the tank it could be too much air to displace although I don't have much experience with those. What do you get with it disconnected and with your hand plugging the pipe?

[mtbreezefarm]

I have torn it apart again and the veins were sticking so after looking closer at them it looks like the previous owner used the wrong size veins as they had cracks and splits and we're jammed into the drum so I resized a second set they gave me but one still sticks after cleaning the whole thing. Even after the new veins and such I reassembled it and tested it only with a gauge and no tank and still maxed at 5 at max rpms. It has a small glass jar with oil that gets pulled by the vaccum as it passes by. The veins tick alitte before it gets oil. The only other number I've found on the pump is ab110 but that doesn't correspond tother any gast number. I also cut and installed new gaskets. So I am no closer to figuring out what the issue might be.

[mountain man maple]

If your looking at the drive side of pump rotation should be counter clockwise. If there is a nameplate on too it should say 1550-v.... Or 1550-p. vanes have to be put into pump with angle going the right way also or it will have low vacuum. Inlet should be on left of pump when looking at drive side. Only other thing to try is eliminate everything put a gauge plumbed to outlet of pump and deadhead to make sure there isn't something your missing on tank.

[whitetail farms]

I also have two gast 1550 that are coupled together and the best I could get was 15 at the releaser with the woods closed off,the other day one of the plastic cooling fans starting rubbing on the motor and now only the back pump it turning and only get 10 at best,gonna replace it with a sihi liquid ring tomorrow

[markct]

How thick were the gaskets you made? Anything more than paper thin will make too much endplay and leakage on the vanes. These are very simple pumps not much to go wrong just gota study the pieces and makes sure they move and fit

[Mike's Sugar Shack]

I have noticed that it seems i can get more vacuum with my oiled 1550 then with oilless 1550.But my oiless is on 500 taps and it will get 17in of vacuum my other 1550 is on 220 taps and i can get 21in with that one.

[WESTMAPLES]

i bought a oiless gast 1550 before last season i was stuck solid took it apart cleaned and freed up the vanes and off it went probly 60 or so hours of running it started lacking vac and the exhuast sounded different took it apart one vane had chipped a corner and was losing vac cfm`s. took it apart and 2 mins with a respirator and a sanding block to striaghten the carbon vane edge and the pump was pulling like new again i did replace it for this season to pull a high vac tho but the 1550 are a handy pump