912UL intermittent rough running

Careful bore scoping a fuel tank, you really need a specialized scope certified for hazardous environments to do this safely. These specIalized scopes have no electronics in the wand and are fully fiber optic and explosion proof. The environment inside an empty fuel tank is quite explosive and using a standard borescope can be dangerous.  The incident rate is low, but the the consequences in a rare event are severe.  

Jeff is correct...you should use a Class 1 Division 2 borescope.  Check with your borescope supplier.  I believe most fiber optic scopes comply but you should check it.  

Cheers

Good features of the disposable gauze fuel filters, I listed,  are that they are:

Almost indestructible

Will not leak

The gauze will not break down & contaminate your carburettor

Can be visually inspected for contamination (blockage)

Come in a wide range of sizes - larger ones tend to have more screen area, so will accommodate more contamination before restricting/blocking fuel flow

Range of micron/filtration specifications (can be hard to get this information)

Light weight

Compact

Can easily be replaced "in the field" with minimal tooling (I always carry a spare or two)

Cheap(ish), - depends on how many you purchase at time & how good you are at "dickering"?

Can be cleaned out using carb cleaner & compressed air, but why bother - they are cheap enough to just replace.

Can be reused on your ground based equipment - mowers etc