Duplicate post or not, I have a comment.
I bought my Vidhata back in 2005 through George Breckinridge and gave it a good look over before ever starting it. I made the governor modification. I cleaned everything I could, including the sump, checking for sand.
Like you, my first thought was a simple in line filter.....one rated for gravity feed........to get rid of the Indian "rope in a dope" filter. I installed an opaque, plastic filter purchased from NAPA and the engine wouldn't start. I checked everything I could think of. Asked numerous questions on this and other forums. God knows how many times I spill timed that thing, but at least I became an expert at it! I finally got disgusted because I had a "lemon" and shoved the engine into a corner where it sat for close to a year.
One fine day I happened to glance at that nice, shiny new filter and noticed something for the first time........an air bubble. Now, the outlet side of the filter was covered in diesel so it SHOULD have flowed easily, but since the filter was at an angle a bubble had formed at the inlet side. It COULDN'T be that simple...could it? Being suspicious, I removed the filter and ran the fuel line straight to the injection pump. It fired on the first crank and settled down at its normal rpm. It honestly never occurred to me that the filter being placed at an angle would block the fuel............but it did.
I ended up modifying the cast iron Indian filter to take a screw in Fleedguard filter and the engine's been a joy since. Moral? Think everything thing through and engines don't run well without fuel.