Small Engines (Lawn Mowers, etc.): roller tiller no gas to carb., compression issue, intake leak

Question
Plug is dry. On timing we had dots alineged but sheared key any reason why? We left crank with dot same place, turned cam rear 180 back to mark, so cam and crank was back to same position . Right? Thanks for your time and patience. Glenn

Answer
If the timing is correct, I can't think of any reason the flywheel key would shear, unless it was partially sheared from a previous and sudden stop by the tiller.  Another way a flywheel key can shear is if the flywheel is either not correctly torqued or the proper compression washers were not used and the flywheel loosened off.  If the plug is dry, the carb is not delivering fuel....agreed?  Three reasons the carb may not be delivering fuel are the carb has issues (just thought of something else to check too....make sure the plate and the mounting surfaces on both the diaphram and the tank connection are not warped), there is an intake leak or there is a compression issue.  Being that most of these engines have a compression release built in to the camshaft, it is difficult to accurately gauge the static compression, so listening for a whisping noise (from a valve leaking) and visual inspection (of the valves) are the best ways to determine if the compression is adequate.  Another problem with the valves can also be the clearance to the tappet.  Off the top of my head, 0.004" - 0.006" clearance on the intake and 0.008" - 0.010" on the exhaust is correct (at least it will run this way...check with a dealer for the exact numbers before you proceed).   Being that it will run with fuel in the carb, I suspect it is still a problem with the carb or the valves need to be lapped to restore compression.  Hope this helps.