If the choke is the only problem then why don't you just put a new electric choke cap on it? Then you just have to play with the adjustments; shouldn't be too hard. There are spec's for adjusting the linkage arm and the speed. Can you find a model number? Maybe post a pic or two?

Here's one style: http://www.ebay.com/itm/ws/eBayISAPI...m=160773809777

and another: http://www.ebay.com/itm/ws/eBayISAPI...m=160759125339
.