Product Review: Motion Pro's Leakdown Test Kit

Oct. 12, 2009 By ORC STAFF
Located in Menlo Park, California, Motion Pro is dedicated to producing the most innovative and unique products for the motorsports industry. The cables, tools, levers and accessories they design are made to exact tolerances with the highest quality materials and workmanship. Their products are the result of years of "hands-on" experience in the shop and on the race track. World Champion Racers and their mechanics rely on Motion Pro to provide them with the right tools for the job. Their products are the standard of the industry... 

   With our cylinder installed and all the fasteners properly torqued to spec, we are now ready for the most important, and often overlooked part of the rebuild! The leakdown test...

The only way to determine a two- stroke engines' overall health and well being is by performing a leakdown test!

Leakdown Test Procedure:

Motion Pro's Leakdown Test Kit
is not only a first rate product with flawless design, every  fitting and adapter to test any modern two stroke engine, and the highest quality construction and components,

  It is also a MUST HAVE tool for anyone that want's to rebuild a two-stroke motor. The only way you can be sure your motor is healthy before you start a jetting procedure is to pressure test it. If you haven't, you are simply wasting your time, and quite possibly, huge sums of money. A leaking engine will almost certainly fail prematurely, if not instantly - and be IMPOSSIBLE to jet correctly... Dune

   It's so easy to use. Even a Glamis squid with a brain that's been damaged from years of race gas sniffing and sand eating can quickly perform... Just 1-2-3 simple steps. If you have the skill to do the top end, the leakdown test is a breeze... Or let's hope a lack of breeze coming out of your 300 buck overhaul!

   The cost of Motion Pro's test kit is less than an average top end job - and a more than wise investment. With the cost of a big bore piston and rings hitting a 100 bucks or more, plus gaskets, bearings, bore-job, etc, the cost of this kit is more than offset by a failed top end due to an engine leak and resulting seizure!

Install the proper flange cover or plug on the exhaust...

Then the proper size pressurizing plug/fitting in the intake boot... Hook the gauge/pump assembly up and start pumping! On a big motor like the 'zilla, it can wear your hand out, so I cheat and blow air in through the intake on the pump bulb with my mouth to get it started. Pump it up to about 6-8 psi.

   What are the results of the test?    FAILURE! What you say? It failed? Well gang, that's why you perform this VERY IMPORTANT test!

At 2-3 psi, air started gushing out of the right side crank seal! The engine would not hold pressure for more than one or two seconds and the gauge would start to quickly drop...

   What now? Well... we pull the primary drive and replace the seal, of course. No problem, done and retested in 20 minutes. The big thing is that had we not done the test, our engine would have sucked air and transmission oil in through the crank seal, leaned out and burned up, provided we were able to even get it jetted well enough to run...    Some tips for testing your engine with the Motion Pro Leakdown Test kit:
  • This is a precision instrument. Keep it clean, and handle it carefully
  • When performing the test, it's a good idea to have a mechanics stethoscope and a spray bottle of WD-40 (water works ok, but tends to run off too fast) to look for leaks if indicated.
  • A motor in good condition should hold pressure for several minutes.
  • NOTE: They WILL not hold pressure indefinitely. Most crank seals will allow some bleeding, and on an engine like the LT500, which is equipped with a complex power valve, frequently they will leak through them, particularly if the O-rings are old or worn. This is not terribly serious but an indicator you should service/overhaul the valve.
  • Always perform a leakdown test when doing a top end. The cost of Motion Pro's kit is far less than a spoiled weekend trip due to a blown motor - not to mention jetting/tuning and performance nightmares!
   With the cylinder installed and fully tested, we are ready to reinstall the primary drive, install the flywheel and button up the side covers.    In closing I have two last tips for you...

Before you install the flywheel, clean and lubricate the inside of it with WD-40 and pay attention to the tapered hub. This will prevent corrosion from forming, as well as keep the flywheel from developing an odd molecular bond to the crankshaft, as they are prone to do. If it does nuke itself to the crank, it can be a bitch to remove down the road!

Using the same Permatex Hi-Tack gasket sealant we used on the base gasket, glue the flywheel and clutch gaskets to their covers. Use sealant on the cover side ONLY! This way, if you have to remove a cover in the field, it can be done easily, quickly and it will leave the gasket intact for reassembly.

Your local dealer can help you get any of the Motion Pro products you need!

Click Here!

Motion Pro, Inc.
119 Independence Drive
Menlo Park, CA 94025 Newsletter
Join our Weekly Newsletter to get the latest off-road news, reviews, events, and alerts!