Talley’s Picks: Motion Pro Leak Down Tester

When you need to diagnose engine problems, sometimes a compression tester isn’t enough to paint a clear picture. That’s where the Motion Pro leak down tester comes in.  

The Motion Pro leak down tester checks possible air leaks through seals or gaskets on engines. It comes complete with an air pressure gauge, pump-up bulb and adapter for single and twin 2-cycle engines. A compression tester tells you if the cylinder is sealing properly, but not much else. Meanwhile, a leak down tester gives you a more comprehensive diagnosis, including whether the piston rings are leaking or the valves are sealing properly. 

When using the Motion Pro leak down tester, you connect it in where the spark plug normally goes, and you set the air pressure to a known value, such as 100 PSI. Next, you release the valve and start pumping air into the cylinder itself while it's at top dead center. Whatever pressure loss there is gives you a picture of the health of the engine. The leak down test helps you determine whether air is escaping through a valve, or to see if air is escaping past the piston and rings into the crankcase.

Here’s what Partzilla’s resident powersports pro John Talley says about Motion Pro leak down testers:

John Talley: I've got yet another Motion Pro tool that came out of my toolbox, and this one is one of my favorites. This leak down tester actually gives you a better picture of what's going on inside of your engine. Now our first go-to is usually just a compression tester, and I like to compare that to taking just a snapshot of the overall health of the engine. 

With the leakdown tester, you can get much more involved as far as figuring out what's going on. Overall, this is going to give you a much better idea of what's going on inside of the engine, and if you need to open it up or not. It could be a different problem that has nothing to do with the mechanical part of the engine itself. This will help you eliminate whether you need to crack that engine open or not. 

Motion Pro makes leak down testers for 2-stroke and 4-stroke engines. Watch the video above to see how to use a Motion Pro leak down tester.