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Discussion Starter · #1 ·
just bought a compression tester form Murray's auto parts store.

i've suspected that i have a leak thorugh my cylinders or somewhere for a bit. blow smoke out exhaust sometimes and am loosing oil somewhere.

want to test compression. have tester, but don't know how to use it

help me!!
 

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King of D'bags
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1.Pull out a spark plug and compare the plugs thread to the fitting on the end of the tester's hose. If they match, screw it into the head. If they do not match, you'll need the appropriate adapter.

2. Crank the engine a few times with the spark disabled. You do NOT want the engine to fire. Watch the needle as it cranks to get a feel for how FAST the cylinder builds it's compression.

3. After a few revolutions, the engine will build its total compression. Note the dial's indication, actuate the bleed off valve, remove tester. Repeat for other cylinder(s).

If there's more than a 10% discrepancy between the cylinders, you've got an issue of some sort.

A leak-down tester is a much better tool for this job. Put the piston at TDC of the compression stroke so that both sets of valves are closed. Stick the bike in gear to lock the crank. Pump air into the cylinder. Watch the dial to see if it drops air pressure too fast. If it does, you've got issues. The next area is where a leak-down tester really exercises its advantage. That air has to be going somewhere. If you hear wind in your tailpipe, you've got exhaust valve sealing issues (bad seat, bent face, etc.). If you hear wind in your crankcase vent (make sure it's disconnected from the airbox for this test BTW), you've got pistion ring issues (scored cyl. walls, damaged rings, etc.). If you have bubbles in your radiator or overflow, it's a head gasket. If you hear wind in your airbox/ carb throats, you've got intake valve sealing issues.
 
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Also you want to make sure that the slides are propper open so that the motor is getting all the air it needs. Learned this on a previous thread.

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Discussion Starter · #7 ·
GraVitY said:
Also you want to make sure that the slides are propper open so that the motor is getting all the air it needs. Learned this on a previous thread.

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how do you do that? aren't they vacumme actuated? should i have the trhottle wide open to let more air in?

or do you take the airbox off and stick your fingers in the carbs?
 

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With vacuum assisted slides take a stick with a tag (so that it doesn't fall in) and prop open the slide. A straw would work great cut appropriately) too just make sure it can't fall into the intake.

More here: http://forum.svrider.com/index.php?topic=57232.0

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I knew I forgot something. ::)
 
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