Kohler CV22S-75534 - Vacuum Issues

Which line are you calling a vacuum line? The fuel pump impluse hose?
 
Now these engine are to have a minimum of 4 inches of vacuum. This needs to be measured with manometer or vacuum gauge.
 
Here is few possibles if the vacuum reading is lower than 4 inches.
 
Crankcase breather clogged or inoperative. NOTE: If breather is integral part of valve cover and
cannot be serviced separately, replace valve cover and recheck pressure. Note: although the service manual says it is non serviceable there is a repair kit for it. Disassemble breather, clean parts thoroughly, check sealing surfaces for flatness, reassemble, and recheck pressure.

Seals and/or gaskets leaking. Loose or improperly torque fasteners.
Replace all worn or damaged seals and gaskets. Make sure all fasteners are tightened securely. Use appropriate torque valves and sequences when necessary.
 
Piston blow by or leaky valves (confirm by inspecting components). Leakdown test can point which these to look at.
Recondition piston, rings, cylinder bore, valves and valves guides.
 
Restricted exhaust. Check exhaust screen/spark arrestor (if equipped). Clean
or replace as needed. Repair or replace any other damaged/restricted muffler or exhaust system parts.

What are the symptoms that lead you to suspect a vacuum leak? If timing is off a bit it will be hard starting with low power. Too far off it won't run. Pretty hard to shear the key on that engine unless the flywheel nut has been tampered with and not properly retorqued.

it is not 100% related to your talk but it seems you can help, I have Dyson dc14 and suddenly its suction power became so meager, Should I replace it or you can recommend something to fix it.