Motion Pro 08-0071 - Manual

MOTION PRO TWO-STROKE LEAK DOWN TESTER P/N 08-0071
Pressure testing is a test performed on a two-stroke engine to ensure that the engine has no air leaks. An air
leak in a two-stroke engine can cause a lean condition in engine fuel-air mixture. This in turn can result in
engine overheating, piston seizure, detonation etc.
WARNING!
Wear eye protection to prevent eye injury from escaping gas and/or flying particles. We recommend that
a qualified mechanic in a properly equipped shop perform this procedure.
1. To leak test the engine: cylinder, head, reed cage, intake manifold and spark plug must all be installed and
torque correctly. Exhaust pipe and carburetor must be removed.
2. Seal round exhaust ports with the correct size rubber expansion plug. For 1986-1991 Honda CR250R and
1985-2001 Honda CR500R, remove the exhaust manifold and seal the exhaust port using one of the flat metal
plates with a rubber gasket. Optional plate 08-071O is available separately for 1987-1989 CR125R. The black
vinyl cap and #32 hose clamp are used to seal the oval exhaust port on 1993-1994 and 1999-2014 YZ250.
3. Insert the correct size carburetor adapter (#1, #2 or #3) into the intake manifold and tighten the manifold
clamp. Teflon tape the thread on the quick coupler and install coupler into the carburetor adapter.
4. Push the nylon hose (from the pump/ gauge assembly) into the quick coupler. If the nylon hose leaks where
installed into the coupler, push the hose into the coupler assembly while under pressure. It is important to have
the system under pressure while attempting to seat the hose to coupler. To remove hose, push green (or gray)
ring on quick coupler towards brass fitting while pulling and twisting hose out.
5. With all test equipment in place and the piston at bottom dead center, use the hand pump to pump 6 PSI of
air pressure into engine. Never exceed 8 PSI of air pressure or damage to the seals and/or engine may occur. If
loss of air pressure occurs, spray soapy water over mating surfaces to see where soap bubbles appear. Repair
any leaks that may appear and redo test. A leakage rate of 1 PSI per minute is acceptable; however the lower
the leakage rate the better your engine will perform.
6. By carefully listening at various points, you may be able to locate air leaks that are not easily accessible with
soapy water. Crankcase seal leakage may be heard by removing the magneto cover or if on primary side may
be heard through the oil filler hole. Leakage at the power valve seals and O-rings can be heard by removing the
power valve linkage covers or through the transmission oil filler hole. On water-cooled engines, head gasket
leakage may show up as bubbles in the radiator coolant.
7. On the Yamaha Banshee, RD 350/400, RZ350 and TZ250 (parallel twins) the center crank seal (labyrinth
seal) will allow low velocity air to pass from one side to the other side. Therefore, both the left and right
cylinders/ crankcases are tested together. To do so, seal both exhaust ports and one intake port. Then, install
the correct carburetor adaptor into the remaining intake port. Perform steps 1 thru 6. There is no way to check
the labyrinth seal; this seal will normally out last the crankshaft main bearings. On Suzuki RM motorcycles, the
power valve breather hoses must be plugged off in order to pressure test the engine correctly. There is no seal
in the power valve chamber.
8. Each leak down tester is tested for leaks at Motion Pro. To insure that your leak down tester remains leak-
proof it should be tested periodically. To test simply connect leak down tester hose to a 1 quart leak proof
container and pressurize to 6 PSI. If no leakage occurs in ten minutes the tester is leak proof. To locate leaks
spray a soapy water solution over fittings and connections and look for soap bubbles. On pipe fittings, use
Teflon tape or pipe sealant. Occasionally, the check valve between the hand pump and hose will leak. Clean the
check valve with contact cleaner and re-grease the ball in the check valve to insure a good seal, and then retest.
I08-0071 04/2012