General OS with a pump?

[Steve Denton]

I’ve been using OS engines since I was a boy. My dad said they were the best and I followed in his footsteps (neat what we learn from our fathers...miss ya dad). Ive never had one with a pump though. This Vibe 90 has an OS 91 with pump and regulator. The heli was used but practically brand new with only a gallon or so through it... then it sat... for years. I put new bearings in it and plumbed all lines as before. My question: the tank is pressurized from the pipe, that’s the way it was when I got her and the thing runs like a Swiss Clock, just perfect! But, should the tank be pressurized from the exhaust pressure of the pipe, or a check valve instead? I’ve looked at the manual online and it shows it plumbed both ways so, which is best? I’m running an onboard glo starter that falls from 1.5 to .8 volts after starting and I’ve never had an engine idle this low before without dying. What’s the pros and cons? Pressurized or check valve? Thanks guys, the more I learn the more I know.

 

[Geena]

I had an OS 91 HZ years ago, on a Synergy N9 that had a fuel pump. It worked well, but It looked a little weird, and there was a little extra wiring. These days, I prefer to have crank case pressure and a check valve, and a regulated carburetor.