What's going to be key is to identify the exact carb you have. It's most likely a Walbro K1-MDC but you'll want to verify before you order a kit and/or tearing it apart. I think the rebuild kit is about $25
Is this the 1965 year model ? I found a parts diagram at this site www.jackssmallengines.com/chainpartmac.cfm They sell some parts but never have dealt with them. If you scroll down a ways you can click on the 250 chainsaw and it will take you to a pdf of the parts description manual. a nice feature if you don't have one. Bordercollie