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Old 15 July 2009, 17:24   #1
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mercury 200 20hp carbs again

K rebuilt the carb but still seem to have a fuel starvation / pump problem.
When i suck fuel into a straw and "blow it " through the air intake starts and revs its nuts off then dies... restarts straight away but not controlable soon as i rev it it cuts out.
My ideas are
A plugs breaking down or other electrical problem??? (have NOT looked into the electrics at all)
B throttle linkage all set wrong or carb mixtures need setting ( i assume its the one top left of air intake) {set it full in then back off but makes no odds it wont start without the helpful blow of fuel
C still a problem with carb / diaphram pump
D sucking air somewhere (cant find any leaks or see any though)
E a problem further in
F ??? Reed valves gummed up (what are they where are they in carb or behind carb in block??)
Bowel fills up when i pump the bulb and air blows trough when float is down stops when float is up so cant see a problem there

puzzling bit is engine starts at about half a pull when fuel is blown in(choke open but choke doesent make any odds on running it)

Is ther oil within these engines (dont think so its a two stroke ) but if so is there a low oil switch (where does the oil go)
Any one got any ideas as its bugging the hell out of me now

Cheers guys allen
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Old 15 July 2009, 18:04   #2
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Originally Posted by AllenF View Post
K rebuilt the carb but still seem to have a fuel starvation / pump problem.
When i suck fuel into a straw and "blow it " through the air intake starts and revs its nuts off then dies... restarts straight away but not controlable soon as i rev it it cuts out.
My ideas are
A plugs breaking down or other electrical problem??? (have NOT looked into the electrics at all)
B throttle linkage all set wrong or carb mixtures need setting ( i assume its the one top left of air intake) {set it full in then back off but makes no odds it wont start without the helpful blow of fuel
C still a problem with carb / diaphram pump
D sucking air somewhere (cant find any leaks or see any though)
E a problem further in
F ??? Reed valves gummed up (what are they where are they in carb or behind carb in block??)
Bowel fills up when i pump the bulb and air blows trough when float is down stops when float is up so cant see a problem there

puzzling bit is engine starts at about half a pull when fuel is blown in(choke open but choke doesent make any odds on running it)

Is ther oil within these engines (dont think so its a two stroke ) but if so is there a low oil switch (where does the oil go)
Any one got any ideas as its bugging the hell out of me now

Cheers guys allen
A-no.
B-Maybe-timing is tied into the throttle inkage too.
C-Maybe-possible blocked jet or air passageway.
D-Unlikely to cause the symptoms you describe unless it's a MASSIVE leak.
E-not a lot else to go wrong apart from...
F-if it's reed valves just scrap it-you'll have to split the crankcases to get to them. They are a rotary reed setup and inside the crankcases.
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