Small Engines (Lawn Mowers, etc.): poulan super xxv, psi drop, vacuum test

Question
i recently came across an old poulan super xxv. the saw had been stored for many years.i cleaned fuel tank replaced fuel lines and cleaned and installed a full carb kit.the saw starts and runs but i cant get a steady idle. i soaked the carb over night in b12 parts and carb cleaner then shot b12 aerosol in all passages then used compressed air. i believe the carb is clean.to replace the fuel line i removed the ign. module.i placed the module at same setting when i reinstalled it .004/0.10mm. is this correct? when i say steady idle i meane it idles fast at times slow sometimes then dies.saw runs very strong at high rpm.any ideas

Answer
hi   cleatus

given the length of staorage time  and your mention of replacing fuel lines and fuel filter
and rebuilding carb with new kit  - making sure to check settings hi /  lo  and metter lever setings , as to igntion unit to flywheel gap it should be 0.010"   a microfische card fold in half is 0.010 " and is good for this job .

too close a setting it may advance tiiming and too wide may retard timming  or even start  poleing

as to uneven idle  given compression and spark appear to be ok  it would suspect  a air leak at either the the carb  to manifold block  or  the manifold block to barrell joint
or even the barrell base gasket , worst case it could be  c/case seals have gone hard
and are not sealing on crankshaft properly  - air leaks usually show up as   uneven / inconsistant idle - hard to start , stalling  rev out too much ( ie wont 4 stroke @ rev )

would pay to  pressure and vacuum test crankcase to find air leak.

you wil have to blank off  manifold block and ex port  and place piston @ bdc  and pressurize  
cylinder/ case through plug hole to  7 psi   and see where air is escaping  as mentioned above
if unit in good order should hold pressure and vacuum for at least 2-- 2.5  minutes  with only 0.5 psi drop

hope this helps   cheers  paul