Pressure Test

Joined
Aug 3, 2009
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Arlington TX
#63
I put a gauge on the carb hole last night, got it up to 10psi with no leaks. Gonna run the gauge inline with my pump tonight and plug the carb port.
 
Joined
Aug 3, 2009
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Location
Arlington TX
#64
Ok, I ran a more accurate gauge inline with my pump. Blocked off everything as discussed before, I removed the aftermarket cap on the flywheel (vs. removing the entire flywheel).
Pumped up to 10psi on the pulse port, no pressure loss at all over 15min. So does this mean I have no leaks?
 
Joined
Mar 8, 2010
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Location
CT
#66
Will a carburator pop off gauge work on the pulse fitting? Im sure it will be a lot more pumps then a bicycle pump but I'm about to do this tomorrow.
 

DAG

No Risk It, No Bisquick
Joined
Apr 19, 2006
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Charlotte, NC
#67
Yes it will work, but will take forever. Go get a large mountainbike tire and cut out the valve steam and attached to 1/4 fule line and the pulse line. Now you have a way to attach a larger pump. You now filet the tire cut to lenght and use as a rubber gasket. Just cut bolts hole anout mount the ruber between exhause mani and cylinder and between intake mani and carbs. Rock Solid.
 
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Mar 8, 2010
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CT
#68
Bought two 1 1/2 test plugs for the intake mani and a 2 inch for the exhaust mani from lowes. I took the dremel to the bottom base on the plug for the exhaust mani, about 1mm all around without touching the rubber expanding part. And a $10 foot pedal pump at walmart and a tire tube. Cut the valve out of the tire tube and wedged it into the pulse line and pumped to 10psi.
 

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DAG

No Risk It, No Bisquick
Joined
Apr 19, 2006
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3,558
Location
Charlotte, NC
#72
tooth pick in each reed set to slightly open them up. You dont want to take those reed screws out to many times considering they tap into plastic. Loctite does not work properly unless there is pressure between internal and external threads...
 
Joined
Apr 9, 2017
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Location
Windsor ON
#75
Thread revival because I used the search function!

At the start of the thread I see it suggested to pump air into one pulse fitting and measure case pressure via the second - maybe I’m crazy here but I was under the impression each side of the case should be sealed off from the other???
 
Joined
Jan 26, 2014
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#76
The Crankcase Areas under each Cylinder are supposed to be isolated (Leak Resistant, not Leak Proof) from each other.

But the Exhaust Manifold is a 2 into 1 type, so this is where the Two sides of the Engine "communicate" anyway during the Leakdown Test and how the Pressure is equalized on both sides of the Engine.

You can Tee a Pressure Gauge between the Schrader Check Valve and the Pulse Fitting so that you only need one Pulse Fitting.

There are many ways to set up this Test. You can also put the Pressure Gauge in the Spark Plug Hole and pump Air thru the Pulse Hose.

As long as the Pressure Gauge comes after the Check Valve and every other Orifice is sealed, then the Test can be done correctly.

Personally, I like to use Rubber Expansion Plugs to block the Exhaust and Intake Manifold Holes. Then I pump Air thru the Pulse Line to check the integrity of the Pulse Line along the way.

8 psi x 10 min
 
Joined
Apr 9, 2017
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Windsor ON
#77
Thanks for the clarification - I actually used some vapor barrier plastic sheeting sandwiched between the exhaust ports and the exhaust manifold (to prevent communication) and the same sandwiched between the carbs and the intake manifold. This worked well and was very simple but I was surprised to hear and feel air escaping from the other pulse fitting, sounds like it’s normal.
 
Joined
Jan 26, 2014
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181
#78
It is normal.

As far as Reed Petals breaking, this would happen during a Backfire or Spitback event or long term Fatigue, but not under a gradual pressurization as is with the Air Leakdown Test.

The Reed Valves are Leak Resistant only. Although its role is that of a One Way Check Valve, they will allow two-way flow. That's why they are not harmed during an Air Leak-down Test.
 
Joined
Jan 26, 2014
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181
#79
The reason for using 8psi as the Test Pressure is because most Primary (Crankcase) Compression Ratios lie between 1.5:1 and 1.4:1 on Stock Engines.

8 psi is the normal operating crankcase pressure (it may spike due to additional Pipe negative and positive pressure though.)

1.5 Ratio usually being the high end of Primary Compression.

1.4 corresponds to 6psi. . CORRECTION: 1.5 corresponds to about <8psi

See Chart.

Crankcase Ratio of Free Air to Compressed Air at Sea Level.jpg
 
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