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coughing on tickover

M

mistercinder

Member
my mercury 50 4 stroke 4 (carb type) coughs on tickover and sometimes cuts out - I thought it might be:

air leaks between carbs and manifold
valve trouble
tight tappets

any ideas?
 
Not much history to go by ---------------------But I would say the carburetors need to be cleaned.--------------The jets and passage ways are very small and plug easily if fuel is left in the carburetors for extended time.-------------------Take them apart and clean them meticulously !
 
try adjusting the idle mixtures to make it richer,1/4 of a turn at a time,see if that helps.worked on my 30hp,3 cyl yami.and my 20hp merc.I also removed the flywhel on my yami and put some drops of oil into the seal lip of the top crank seal.helps to reseal it.good place to suck air.seemed to make a difference
 
When cleaning carbs as per the above post by racerone, what solvent is good to use on two stroke and four stroke carbs?
 
wynjim55 said:
When cleaning carbs as per the above post by racerone, what solvent is good to use on two stroke and four stroke carbs?
Click to expand...
Lacquer/automotive paint thinners is excellent. grab an old ice cream tub or coffee tin and soak the arts in that. BUT! No plastic parts in the thinners please. Buy a tin of thinners at the local auto store.
 
thank you for your replies - my engine is march 1999 4stroke 4 cyl (carbs) - the manual says the air screws are non adjustable but on my engine they are! - carbs have been meticulously cleaned and all jets are correct - I have set air screws at 2.5 turns out on each carb as per the manual - when I cleaned carbs I noticed O ring seals (8) on the carb to manifold plate looked squashed and worn - I think I'll replace these initially as it's easy to do - I found one suppressor cap was open circuit so I replaced that - I take your point on the weak tickover mixture so if the O rings don't work I'll try an air screw adjustment as 2.5 turns out is, according to the manual only a suggested start adjustment - otherwise I guess I need to check timimg belt fitting is ok, valve sealing and tappet clearance? - I don't really want to remove the cyl head unless I have to!
 
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