Leak down test

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Apr 11, 2025 | 10:21 PM

#21

Since 1968

Road Master

Joined: Jun 2019

Posts: 952

Likes: 528

From: Richmond TX

The one and only time I did a leakdown test I managed to stop the pistons from moving by sitting on the bike with one foot on the rear brake. I like the locking bar idea and testing in several piston locations.

Apr 11, 2025 | 11:10 PM

#22

Lonewolf176

Stellar HDF Member

Joined: Sep 2007

Posts: 2,434

Likes: 658

From: Vancouver Island B.C.

Jims also makes a tool. $$ but locks the flywheel in any position.
https://www.zippersperformance.com/758-753/

Apr 12, 2025 | 12:08 PM

#23

djl

HDF Community Team

Joined: Jun 2006

Posts: 12,763

Likes: 2,597

From: san antonio

Quote:

Originally Posted by Lonewolf176

Jims also makes a tool. $$ but locks the flywheel in any position.
https://www.zippersperformance.com/758-753/

That's the one I use.

Apr 14, 2025 | 09:41 AM

#24

Fat11Lo

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Joined: Mar 2012

Posts: 2,008

Likes: 596

From: Columbus, OH

Quote:

Originally Posted by Lonewolf176

Jims also makes a tool. $$ but locks the flywheel in any position.
https://www.zippersperformance.com/758-753/

I have that one
Now if they would make any for the M8 again I'd Be happy

Apr 14, 2025 | 10:40 AM

#25

DK Custom

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Joined: Nov 2010

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From: Hickory Flat, Mississippi

A leak down test is a good diagnostic test to see the condition of the seal of the rings and the valves.

A compression test is not sufficient. With a compression test a cylinder may have "good" compression, but it does NOT tell you if there is a bad valve seat seal.

Here's a video on how to do a Leak-Down and what the results indicate.

Kevin

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Apr 21, 2025 | 12:18 PM

#26

Dan89FLSTC

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Joined: May 2008

Posts: 21,026

Likes: 12,549

From: South Carolina

Quote:

Originally Posted by DK Custom

With a compression test a cylinder may have "good" compression, but it does NOT tell you if there is a bad valve seat seal.
Kevin

If a cylinder has a bad valve seat seal, it will have low compression, and the engine must be disassembled and repaired.

If a cylinder has good compression, there is no need to look further.

And in the case of the original post in this thread (where there was no problem to begin with) there was no reason for a compression check or a leakdown test.

If an engine is performing well and not burning oil, leave the compression tester and leak down tester in the tool cabinet.

The FAA does not require leak down tests every 100 hours on motorcycles...