Bob,

There is a brass bushing that rides between the crank and the hole for the regulator feed, some engines were affected where that bushing would rotate for some odd reason and block the passage. If that is the case you might want to contact your YS agent about repair or replacement.

As for cleaning everything, I use raw fuel or isopropyl for cleaning as it does not attack anything. Cleaning the carbon off the valves is easily accomplished by using an exacto knife and lightly scraping until clean, again I use a bin of raw fuel to submerged the valve in while I do this.

You could use baking soda or toothpaste for lapping of the valves if you think it necessary, but unless they are not sealing I would not bother.

Pete