disaapointing leakdown test
HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
You indicate that you are happy with the way the bike runs, so why the leakdown test?
No engine will have perfect sealing with zero percentage loss. Five to 10 percent loss indicates an engine in great to good running order. An engine between 10 and 20 percent can still run okay, but it’ll be time to keep an eye (or ear) on things. Above 20 percent loss and it may be time for a teardown and rebuild. Thirty percent? Major problems. The percent of leakage should also be consistent across the cylinders. Any great differences indicate a problem in that cylinder.
There are only two places the cylinder can lose the seal; the rings or valves. When a leakdown test is done, the tester can hear the leakage, i.e., exhaust valve will "hissssss" out the exhaust pipe; intake valve will "hisssss" out the intake track; rings will "hisssss' out the crankcase vents. Whoever did the test should have been able to hear where the leak was coming from. Actually, you could also lose the seal at the head gasket but you wouln't need a leak down test to find that leak.
It the valves are leaking, pull the heads and send them to BigBoyz for their $299 "street" port job. If it's the rings, ride it until the low cylinder hits 20% leakdown and freshen up the topend.
No engine will have perfect sealing with zero percentage loss. Five to 10 percent loss indicates an engine in great to good running order. An engine between 10 and 20 percent can still run okay, but it’ll be time to keep an eye (or ear) on things. Above 20 percent loss and it may be time for a teardown and rebuild. Thirty percent? Major problems. The percent of leakage should also be consistent across the cylinders. Any great differences indicate a problem in that cylinder.
There are only two places the cylinder can lose the seal; the rings or valves. When a leakdown test is done, the tester can hear the leakage, i.e., exhaust valve will "hissssss" out the exhaust pipe; intake valve will "hisssss" out the intake track; rings will "hisssss' out the crankcase vents. Whoever did the test should have been able to hear where the leak was coming from. Actually, you could also lose the seal at the head gasket but you wouln't need a leak down test to find that leak.
It the valves are leaking, pull the heads and send them to BigBoyz for their $299 "street" port job. If it's the rings, ride it until the low cylinder hits 20% leakdown and freshen up the topend.
Last edited by djl; Nov 17, 2010 at 12:02 PM.
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