Topic: Compression test:Is it too late with the engine out?

[denward17]

I have my engine out and just thought of doing a compression test (I know it would have been easier to do with it in the frame, but I have a habit of doing things backwards sometimes).

I took it out to clean and replace the pucks (oil leak).  But something is nagging at me to perform either a compression test (cold) (with kick starter) or a leak down test.

What are my options with a cold engine and the oil drained?
Engine has 22k miles.

Thanks in advance.

[Flyin900]

A leak down test is the gold standard vs a compression test. A leak down kit can be purchased off Amazon for around $50 or less in a blow moulded case. You just need a small compressor and I usually run 50-75 lbs into each cylinder being tested.
It will give you a good idea of the condition of the motor, yet if your pulling the head I would expect you will do some type of valve work/clean up while your in there.

[BenelliSEI]

Leak down would be OK. A reasonable compression test would be best on the electric starter. Not a good idea unless you hook up a temp oil tank (and put the oil filter back on?).

[newday777]

A leak down test is the gold standard vs a compression test. A leak down kit can be purchased off Amazon for around $50 or less in a blow moulded case.

Not available.......

[Tracksnblades1]

A leak down test is the gold standard vs a compression test. A leak down kit can be purchased off Amazon for around $50 or less in a blow moulded case. You just need a small compressor and I usually run 50-75 lbs into each cylinder being tested.
It will give you a good idea of the condition of the motor, yet if your pulling the head I would expect you will do some type of valve work/clean up while your in there.

+1

Check local sources you can may be able to rent a leak down tester.
Some are calibrated @ 100 psig, make sure your on TDC..

[Flyin900]

A leak down test is the gold standard vs a compression test. A leak down kit can be purchased off Amazon for around $50 or less in a blow moulded case.

Not available.......

Lots available on Amazon when I looked recently, not just one item that you have indicated. Local automotive parts stores may have them for rent for free too as noted. Deposit is returned after the tool is returned in good condition.

[denward17]

I checked with a couple of local auto parts stores that do loaner tools, neither had a leak down tester, so I went on amazon and ordered one.  This one is supposed to let you dial the input pressure up to 100psi.  I guess I will find out.

Thanks Guys...

[HondaMan]

A word of caution:
if you spin the engine without the oil tank connected (and full of oil) you will pump out the oil in the pressure side of the oil pump. At the very least, this will cause you a [very] difficult time of re-priming the oil pump when you put it back together, causing 0 oil pressure. Consider rigging up a way to connect the oil tank with oil aboard before spinning that baby with the starter. I have a spare 77/78K oil tank (but no hoses!) if you want it, for postage.

You won't likely be able to do this with the kickstarter, out of the frame.

[denward17]

A word of caution:
if you spin the engine without the oil tank connected (and full of oil) you will pump out the oil in the pressure side of the oil pump. At the very least, this will cause you a [very] difficult time of re-priming the oil pump when you put it back together, causing 0 oil pressure. Consider rigging up a way to connect the oil tank with oil aboard before spinning that baby with the starter. I have a spare 77/78K oil tank (but no hoses!) if you want it, for postage.

You won't likely be able to do this with the kickstarter, out of the frame.

Thanks Mark, I decided just to do a leak down test, so no spinning.  Hopefully just getting it to TDC a few times won't hurt.  When back together will kick start many times to prime the oil pump before trying to start.

[HondaMan]

A word of caution:
if you spin the engine without the oil tank connected (and full of oil) you will pump out the oil in the pressure side of the oil pump. At the very least, this will cause you a [very] difficult time of re-priming the oil pump when you put it back together, causing 0 oil pressure. Consider rigging up a way to connect the oil tank with oil aboard before spinning that baby with the starter. I have a spare 77/78K oil tank (but no hoses!) if you want it, for postage.

You won't likely be able to do this with the kickstarter, out of the frame.

Thanks Mark, I decided just to do a leak down test, so no spinning.  Hopefully just getting it to TDC a few times won't hurt.  When back together will kick start many times to prime the oil pump before trying to start.

I have modified my advice about re-priming these pumps lately: while the steps found in my book are still valid, I have ADDED the extra step of pouring at least 1/2 quart of oil into the engine (thru a valve tappet's cover, with a little bitty funnel...) to help the pump. What this does is: the shaft seal in between the 2 pump halves is now getting pretty stiff (if you didn't change it) and when the suction side of the pump is empty it lowers the suction in the pressure side's impeller by letting it suck thru the shaft seal. This takes less vacuum than pulling oil from the tank, so it can make re-priming troublesome. So, pour some in after the engine is back in the frame and the tank hooked up and oiled up with at least 2.5 quarts (in the post-1975 smaller tanks). If it is cold in the garage, maybe also put an electric heater right up against those oil hoses for a while (I do it for an hour in 20 degree weather here) to make sure the oil in the hose isn't too stiff for the low vacuum. The volume of the hose is enough oil to fill the pump's pressure impeller, which then usually kicks things off well.