merc sport jet 120xr poor idle/high speed

kend301

Lieutenant Junior Grade
Joined
Jul 4, 2009
Messages
1,005
Re: merc sport jet 120xr poor idle/high speed

Start by hooking the pressure gauge to the rubber line to the top carb , then the bottom , Post results , I still think you have a clogged fuel line .
 

slummer

Cadet
Joined
Jul 22, 2010
Messages
16
Re: merc sport jet 120xr poor idle/high speed

4 psi to the top carb
When checking the bottom carb (which tee's through the top carb) the reading was also 4 psi while cranking but dropped and held at 2 psi when I stopped cranking.
 

slummer

Cadet
Joined
Jul 22, 2010
Messages
16
Re: merc sport jet 120xr poor idle/high speed

I pulled the reed boxes and found several broken reeds in both the top and bottom. One was snapped off completely but I cannot find any of the peices. I think installing new reeds will solve my starting problem but what about the missing broken parts. Do I have to pull the pistons out ?
 

kend301

Lieutenant Junior Grade
Joined
Jul 4, 2009
Messages
1,005
Re: merc sport jet 120xr poor idle/high speed

That was going to be my next suggestion , I need to see the fuel/air flow in your motor , I know you do not have to pull the pistons ect but there may be a cleaning procedure if you are missing large pieces .
 

slummer

Cadet
Joined
Jul 22, 2010
Messages
16
Re: merc sport jet 120xr poor idle/high speed

cyl #1 has one reed missing completely
cyl #2 has two cracked reeds
cyl #3 has three reeds not sealing
cyl #4 is missing one half of a reed

It's a wonder this engine ran at all
Are these motors prone to reeds breaking like this? and would you know the cause?
 
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