build and use a leakdown tester (2024)

this should be used ANYtime you remove or redo the top end or whole motor or if you are having jetting issues.

Step 1. take your carb or intake boot to homedepot, lowes etc. and head for the PVC fitting isle, and find an end cap with a threaded hole about the right size so that it can be stuffed into the intake and clamped down.

Step 2. go to the air fitting dept and get a brass T, a schrader valve (tire valve) and a low pressure guage 10~20 psi, and 2 barbed fittings, one that fits the 'T' and one that fits the pvc. you may meed a reducer or two. if you are having trouble figureing it out, the guy at the store can hook you up. assemble the pieces into something resembeling the picture. to seal the exhaust port, get a piece of sheet metal, aluminum etc., cut it out about the size of the exhaust manifold, maybe a little bigger, measure the distance between the exhaust studs and drill 2 holes. take some rubber (like an old innertube) and cut out a piece to use as a gasket between the piece of metal and the cylinder.

Step3. pull the exhause manifold off and use it to sandwhich the rubber abd mettal and tighten it up, and install your contraption in the intake boot.

step 4. use a bicycle pump (not the aircompressor!) to pressurize the motor to 7psi and wait 5 minutes. If the airpressure goes down more than 1 psi or so you have an air leak. take an old windex type squirt bottle and put some dish soap and water in it and start squirting the motor, head gasket, base gasket, intake gasket.. and look fo bubbles. if you find bubbles you found your leak. if no bubbles, squirt the seam all the way around where the case halves come together. if still no leaks start taking things apart and checking the main bearing seals. simple.

awsome man. another thanks.

your becoming an awsome help to this forum quickly, dude.

tjsdaname said:

here is a dumb question for you
you do this when the top-end is still connected to the bottom end right????

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yes, i was gonna say that before i stickied it

Here is the one I just made for $20 at Menards.

It has a 0 -100 psi, but I'm going to change it out with a gauge I already had at the house. I just liked the way the gauge, valve and housing was put together.

back up to the top with this, lots of guys having engine problems lately

sticky maybe?

i will add to this:

ur vent line to the crankcase has to be pluged

stephen12091985 said:

i will add to this:

ur vent line to the crankcase has to be pluged

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No it doesn't. the crankcase vent goes to the tranny which is completely seperate. having it plugged or not makes no difference, however not plugging it you can spray it to check for bubbles, which would mean the sealent between the case halves is leaking pressure into the transmission.

TopTechKid27 said:

great DIY! i will say tho is in school i was always taught to use static pressure not positive pressure other wise you run the risk of blowing seals out even tho its unlikely.

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Static pressure I assume would be ambient/atmospheric pressure, in which case you would not be able to read and kind of pressure or change. So yuo need positive pressure but only about 7 pounds or so. If you hit it with a standard home aircompressor, 120 psi will blow the seals into next week though....