Squealing and stalling at high revs..

[straytcat]

My new to me rt25 runs fine at lower rpms, but when I rev it up, it starts to squeal; it's not a fan belt, but that what it sounds like. Then it will quit moving suddenly, when I lower the rpms it will move again. A knowledgeable friend thinks it could be the drive coupling between the engine and the pump. Any suggestions? Thanks.