Some great advice out there already!!
Violet, I agree that getting to know these people and showing them more of your charming self could be a way to go - it happens at parties that people just split up, so then just join the next group and start talking about something random (or compliment the pie?) Sometimes it's also good to offer to 'help out' or pass the desserts or such? People also LOVE to talk about themselves, or eg trips they've taken etc, so you could also ask eg 'So, what have you been up to recently?' or such, until you find some good topic interesting to both/all of you... (and/or people interesting to talk to)
If you get along with men well, and women have seen it, it might be pereceived as a possible 'threat' too, but you can charm them silly and render yourself 'harmless' too... (there's just a slightly different way to talking with women than with men, we're all human tho

) Maybe they're just shy, or 'shy to strangers' - people can be comfortable in a circle of people they know, someone new comes and they get shy. So it may be good to 'pull them out of their shell' like Jewel said.
Maybe one or a few of these women may also have 'motorcycle phobia' or bad opinion against motrocycles (eg my mum has it, she thinks they're way too dangerous etc) and maybe they didn't dare to say anything because they don't know you so well, but didn't know what else to talk about... or just didn't find a common topic... if they only ever talk about stuff they might think you wouldn't be interested in, they may not know what to talk about..
Also, you might be doing some 'flirty' or 'malespeak' behaviour subconsciously - a few of my friends do that, and they usually get along better with men too... Being different (dress, interests etc.) can be perceived as 'strange', but if they get to know you better, or you find some common interests, they can also start seeing you as 'fabulous'!!