Cashing in IRA funds to buy a bike is probably a very BAD idea. Not only will you have to pay a LARGE fee for withdrawing the funds, you will also get nailed tax-wise at the end of the year. The whole thing will probably cost you upwards of 30-35% of what you withdraw, maybe even more.
Some IRA's allow you to take loans against them. The great thing here is that the interest you pay on the loan, you are actually paying to yourself. Look into that before you think about taking a disbursement. If not, then just save up. You'll be glad you did.