Depends what you can get in the swing arm, as std it would have 2.75x21 front, and 4.10 x 18 rear.
In most older hondas you could just about squeeze in a 110/90 x 18.
You have to be aware of the older ie 4.10 x 18 markings(IMPERIAL) AS OPPOSED TO THE NEWER MARKINGS 110/90 x 18 which are a MIX.
The first number is width in MM the second is aspect ratio as a percentage, then the third numbe ris the diametre in INCHES.
tabetha