If that Vendo 90 were priced reasonable, ( like less than $200.00 ),
you could pull the compressor and swap it with the 81 if you found it to be bad.
There's an idea, but I am pretty much doubting that the guy is going to swallow a $1,350 price reduction. I'd be afraid to even make an offer that much below asking, he's liable to thump me one. Don't think I'll even go to look at it.
The guy with the Vendo 81 has a couple of other items I might be interested in....maybe I can make a package deal.
