Mikee Minute #7 -- Compression vs.leakdown tests

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mikenixon
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Mikee Minute #7 -- Compression vs.leakdown tests

#1

Post by mikenixon »

As to the reasons for using each, compression tester and leakdown tester, it is not correct to say the leakdown tester obsoletes the compression tester.  For, while the leakdown tester can find things the compression tester cannot, the reverse is also true, the compression tester can find things the leakdown tester cannot.  You simply have to know when to use each, and in many cases you will use both.  For example, a leakdown test indicates below 10 percent on a hypothetical engine, yet it has gradually lost power. A compression test that is low, yet leakdown has exhonerated the valves and piston rings, will then make the technician wonder about an excessively worn cam chain, common by the way on dirt bikes.  That is, they wear their cam chains faster than do road bikes.  A worn cam chain on a dirt bike or a chain that has jumprd time (or cam chain or belt that been misassembled on a road bike) will retard cam timing enough to dramatically affect cylinder compression.  Make sense?  
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05c50
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Re: Mikee Minute #7 -- Compression vs.leakdown tests

#2

Post by 05c50 »

Good point Mike. In my years of working of cars, a leak down test would not always show a worn (jumped) timing chain, a worn cam lobe, a worn valve guide, or a broken valve spring. All of these were somewhat common back in the seventies. Could apply to bike engines also.


........Paul
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