I have the same issue, but a funkily shaped 'Nana sorted that out.
Maybe move the seat post mounting bracket back?
Mine rides better than stock, here's a pic:
I'm really digging the white seat on there, flows pretty well and picks up the other white. Wheels are white (ish) alum Electras.
Of course, tube has a puncture, as does tire, but its a good start!
Rusty but still usable Swing Bike frame, fork and $75 worth of fancy seat post for sale , $250 plus shipping(breaking even, pretty much) Pic of it's recent build for inspiration:
I popped on some test rims...Sadly my 3" beach bum won't fit!
I've a 1.75 and a 2.125 on there, I love the subtle fatness to the rear.
Photos tomorrow!
She's slowly getting there. That's a Euro coffee tank,01 GSXR front end, shortened and stepped seat, larger mikunis and Bassani pipes. Soon to have Daytona wheels(maybe) and spec 2 pipes!
Thought has crossed my mind, But I was really trying to avoid building another muscle bike, and wanted to use as many parts I already have nearby as possible.
Lucky to have bought the 24" frame, I guess :wondering: