Do i need longer forks when using 3 deg raked neck cups on my 1988 Sportster

SOURCE: what is the steering neck rake in a 82 lowrider?

The FXS Low Riders had a 32 degree rake, but the FXRS and FXLR Low Riders had a 29 degree rake and the FXRS-SP, FXRS-Conv Low Riders had 31 degrees.  The first Dyna Low Rider in '93, the FXDL, went back to 32 degrees.  There have been four different frames under the Low Rider model name.

SOURCE: What is the neck rake in a 2000 FXST Softail?

Its raked out at 32 degrees

SOURCE: 2008 HD xl1200c sportster fork lock removal.

grind off the rivet.then lock should pull out, then use a slide hammer to pull out the rest of rivet

SOURCE: need the dry capacity on my 883L forks

12.3 ounces each side

Testimonial: "Thanks for the info. Geoff"

SOURCE: I have a 2006 Harley

You didn't say which Dyna series bike you have but I'm going to say that Sportster specs are not the same as for a Dyna. If you think you have a gap between your triple tree and the steering head of the bike, something may not be assembled correctly. I'd take to a shop or a dealer and have them check the front end.

Good Luck
Steve