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engine tests

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how do i perform leak down tests, and crankseals test on my 73' suzuki gt550?

SPEED!!! My new anit-drug
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Capitol A

Here's how we tested Geeto's crank seals on his T500:

We did a leakdown test on Geeto67's 71 Titan today. I cobbled together the leakdown test equipment out of:

1. A basketball pump with gauge (marked in 5 PSI increments) from Sports Authority $9.99
2. A 2" test plug from the plumbing section for the exhaust from Home Depot $3.49
3. A block off plate for the intake made from scrap 1/8" lexan - free
4. A fitting for the spark plug hole cobbled together from a "HELP!" brand spark plug non-fouler (get the 14mm SHORT package) $3.99 for two and a tire valve stem JB welded into it.

The spark plug "non-fouler" is a hollow fitting shaped like the bottom of a spark plug with 14mm external threads at the base and a 14mm internal thread at the top. I guess you use these to move the plug up out of the combustion chamber to keep it from fouling although it seems to me they would rob the engine of power as well..... I trimmed down the base of the tire valve with a pair of scissors and screwed it into the non-fouler. Then I put a bead of JB Weld into the top of the non-fouler packed in around the valve stem. All in all it worked well.

The right side wouldn't pressurize at all and the left would pop out the exhaust plug at 5 PSI. This told us that his right outer seal is leaking (plus the hissing noise from the seal was a pretty good giveaway as well).... For the left I guess I either need to make a block off plate from lexan like the intake or wrap the expanding rubber insert on the 2" plug with some stretch tape to get it to seal better.

Each cylinder should hold 6 PSI for 6 minutes. Don't use much more pressure than 6 PSI because you can damage the seals this way

Rather than the expansion plugs you can use a piece of plexiglass (Home Depot) or flat aluminum plate, backed with inner-tube rubber, held on with the stock exhaust collar.

Hope this helps!

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Sorry - it took me a little while to get back to this thread.

Check your cylinders with a compression tester. Sears sells them for under $30. Get one that has the screw in fitting for the spark plug hole. Switch off, gas off, throttle WFO, and use the kick starter. You're looking for compression over 100 PSI as your minimum. 115 - 125 is good. All three cylinders should be no more than 5-10 PSI different.

Use the 6PSI pressure test for your crank seals. Sorry I described more how to build your test equipment and really didn't cover how to perform the test! Pull the spark plug on the cylinder you want to test. Seal the intake and exhaust ports as described above. Rotate the engine until the piston is below the transfer ports. It doesn't have to be exactly BDC but the upper transfers should be clear. Slowly pressurize the cylinder with your basketball pump until you get to 5-6 PSI. Watch the gauge and see if it will hold that 5-6 PSI for about 6 minutes. Usually it's really obvious if your crank seals are bad as you won't be able to pressurize the cylinder in the first place. Sometimes you have a seal on the edge and the pressure test is the last straw for the seal. This is actually better than having it fail while running though.

If you need the crank rebuilt, I can recommend several rebuilders that are good. It will cost you about $150 to $200 and you'll need to buy all the required seals for the rebuilder. Plus it's good to replace the big end rod bearings and thrust washers while you are at it....

Hope this helps!

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