Lionel Jr. 1700 and 0-27 track

I don't know about that set, but this is what I know about Lionel Jr. trains:

• Lionel Bought Ives and continued that line of trains for a few years.
  Ives had a single page of trains called Yankee Complete Electric Outfits in their 1932 catalog.
  They sold No. 1013 Yankee curved track (27" diameter) for the Yankee Outfit trains.
• Lionel introduced Lionel-Ives trains in their 1933 catalog.
  They sold No. 1013 Lionel-Ives curved track (27" diameter) for the Lionel-Ives trains.
• Lionel dropped the Ives name in their 1934 catalog and they sold trains under the name Lionel Jr. until 1936.
  They sold No. 1013 Lionel Junior curved track (27" diameter) for the Lionel Jr. trains.
• Lionel dropped the Junior from their catalog in 1937 and introduced the new concept of "O27".
  They sold No. 1013 Lionel "O27" curved track (27" diameter) for the Lionel "O27" trains.
• Lionel continued selling O27 curved track as No. 1013 in the post war years.

I had the 1700 Lionel Jr set as a kid and it ran on our 027 track without any problem

I’ve run mine on both 027 and regular 0 tubular track with no trouble.  Turnouts can be tricky, though.