Wilburn , As a former Diesel Mechanic , I have seen the damage a Carbon Fouled engine can obtain . Back in the day we use to inject a fine mist of water within the intake to break down carbon with the engine running . However with small gas engines as advised you must be careful . In the day small engines had a hour limit for require decarbonizing , 200 hrs normally . Pull the heads and brush the heads , piston crown and clear the ring lands etc. Replace the head gasket and retorgue the heads. Today proper use of fuel treatments , MMO , Sea Foam , Startron will ensure carbon and carburator fouling issues are greatly reduced .
Personally I have added a few ounces of tranny fluid to assist in quieting noisy lifters and lubricate valves and guides . I would believe any solvent based cleaner used prudently (small dose) will gradually loosen and reduce carbon fouling , however use of new high grade gas fuel with additives already provided within the fuel will do the same . Common sense prevails Lucas top end lubricant has both solvent and lubricity , which I believe is the safest additive for older engines , Seafoam in 1 ounce increments will provide the same assurance . Normally the worst case is fouling or bridging of plugs with carbon whe excessive treatment is used . Realize this is an old thread , hope it finds you in Good Health Wilburn and usefull additional information for others !