Recommended borescope

Perhaps that's why the Rotax maintenance manual recommends to check the compression by the differential pressure method, (aka leak-down).

Thanks.

Michael I did a lot of research and much of it was on Amazon and most everything there had a lot of poor reviews, but eventually I took the the plunge and bought a Teslong model ‎NTS500B for $120.  It has a tiny (5mm) camera which was my top requirement. I bought it last June and have used it several times on my aircraft and around the house- they are handy for other things than engine cylinder inspections. I used it to inspect a possible fuel system connection leak, a fuel sending unit issue, an annual corrosion inspection of my lift strut tubes, etc. etc.  I’m happy with it. The flex cable will hold its shape when snaking it around and the camera focus and image work well.

Hope this helps.

Please forgive my ignorance, but why do general aviation such as Lycoming and Continental engines just do a compression test and that is considered adequate rather than a differential compression test as Rotax specifies? Does the differential compression test eliminate the need for using a borescope? Thank you all for your thoughtful comments.

All

Differential pressure testing is always the preferred method for aircraft engines.  You have the ability to know if pressure loss is from the valve, exhaust vs intake, or rings to cylinder.  In addition the amount of loss tells you how much wear is abnormal.  Peak pressure tests only give you a quick reference and no detail, you will be in the dark with a understanding what that low peak pressure is, valve, rings or whatever.  

The idea of a borescope is to give you additional information in the event of strange readings or poor running.  It is not always just about the pressure and seeing the back of the valve, bore, valve seat, might give you a lot of detail missing with just a pressure test.  

Just my opinion.

Cheers