process of elimination

[Barrie2777]

These were the steps I went through to fix an engine which would not idle and the gas in the line would always seep back to the tank. Both symptoms indicated an air leak somewhere.
1-changed the white plastic cap on the carb, suspected a small crack alowing the gas to seep backwards
2-seepage was worse
3-screwed a fuel filter onto the carb
4-seepage still occurring
5-removed the fine brass screen, replaced the fuel filter
6-seepage problem fixed
7-removed carb from engine, separated the spacer block and all gaskets.
8-applied gasket maker on all surfaces
9-reattached the carb
10-still no idle, have to go deeper into the engine
11-removed the clutch and oil seal on that side. Found the seal to be installed backwards and suppling no seal on the crankshaft
12-installed new seal
13-removed flywheel side seal and found a different make of seal but still not providing a seal on the crankshaft
14-After running the engine to operating temp, an idle was established.
Fixing the problems with these engines is not often difficult but should be approached in a systematic way, eliminating what may be a simple problem and work your way up to the big problem if there is in fact a big problem.