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reed box or lower seal

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flattop1

New member
Johnson 140 runs poorly below 2000 rpm what symptom would the lower seal or reed box give me ? engine has good spark and compression.
checked for clogged jet.
Thanks
 
140tl78c
Idle timing is four degrees before tdc. Have not checked key.
I had the Reed box off and two stuffers would not stay in place.
I held them in with a metal ruler then slide ruler out is why I'm wondering about that.
 
okay got a spark tester good strong spark 7/16 inch.
1-4 122, 130 , 127 ,125
did full carb kits welch plugs out.
engine been down/apart 10 years any chance 4 reed gaskets could be leaking?
idle is better still dies coming in to dock , no sputtering.
plugs clean an brown / grey.
any way to check for water leak at exhaust plate?
no broken rings 2 new pistons are rering 2.
thanks.
 
new gaskets through out. have sprayed with aerosol can to check.
did full disassembly and assembly.
does not seem to spit fuel.
 
Last edited:
faztbullet said:
You mean to say they re-ringed 2 original pistons???Have you rebuilt fuel pump?
Click to expand...
yes . I did, engine had 300 hrs on full pro rebuild. which was done with huge error only 16needles in lower
bearings where it needed 18. so cage broke.
have not rebuilt fuel pump. runs out great when you open the throttle . I guess thats next, fresh fuel within last 30 days.

I will spray again with soapy water
so any possibility upper or lower seal could be sucking air at idle speed?
 
A cylinder drop test will tell you which cylinder is not firing. While running pull a plug wire and quickly put it back on. The engine should respond the same on all four cylinders. For the V engines you notice the difference when you put the plug wire back on more than when you remove it. When there is a leak in the crankcase it is not sucking air as much as it is losing precharge that pushes the fuel mix into the cylinder when the piston reaches the bottom of the stroke. A vacuum leak would be an issue between the reeds and the carb gasket or manifold gasket.
 
thanks
I have a mychron for the kart I can use to monitor each cylinder individually .for correct rpm reading per cylinder (maybe)
I will try it any way one wire hookup.
 
The soap test revealed a small leak at the exhaust plate. bolts were slightly loose. tightened them and it disappeared. sprayed everything front too rear.
drop test did not reveal any thing substantial .
fresh hi test fuel was an improvement.
also changed idle jets as they were .010 oversize.
will test on water next.
Thanks
 
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drop test :
It aways fun pulling plug wires standing in water.
rubber boots , insulated pliers and leather gloves , sill get the shock treatment's.
 
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