dcarver
Well-known member
Would it hurt anything to run a quick compression test, say 4 short 10-second starting bursts, given no oil in the crankcase?
Compression testing -
- Thread starter dcarver
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wfooshee
O, Woe is me!!
I wouldn't do it myself. But since you really ought to "rinse" the oil pan with a change or two, to make sure you get the water out, I think you could be efficient and combine those rinses with your compression testing.
Put in some oil, do your test, drain it again. You might think about another fill/drain cycle, too. You absolutely want to coat all surfaces with good, non-watered oil, escpecially if it's gonna have to sit a while. Nothing rusts like steel parts that have been hot and wet.
Put in some oil, do your test, drain it again. You might think about another fill/drain cycle, too. You absolutely want to coat all surfaces with good, non-watered oil, escpecially if it's gonna have to sit a while. Nothing rusts like steel parts that have been hot and wet.
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FJRay
Well-known member
I would think there is enough residual oil film for a comp test. Under ideal conditions a comp test wants to be at operating temp and wide open throttle but for your test I would go for it.IMHO
LAF
Well-known member
I do not think it would be a good test. If you do not have good oil for the rings then it would not provide valid readings. Also you need to expand all the metal to operating temps. Cylinder, pistons, and rings.
I dont even think you could do a leak down test with out known good oil on the rings of the pistons, and cylinder walls.
I dont even think you could do a leak down test with out known good oil on the rings of the pistons, and cylinder walls.
RaYzerman19
Go Wings!
A cold engine compression test won't tell you much except that you do have some compression. Valid readings only happen with a warmed up engine where oil has coated everything including the cylinder walls. And hot or cold, NEVAR run an engine with no oil. You risk scoring the cam, con rod and crank bearings, and the cylinder walls. Ain't worth it.
Alternate test is a leakdown test, using compressed air into a spark plug adapter with engine rotated to compression stroke for the cylinder being tested, and crankshaft held in that position. But, again, not that valid without oil coating everything.
Alternate test is a leakdown test, using compressed air into a spark plug adapter with engine rotated to compression stroke for the cylinder being tested, and crankshaft held in that position. But, again, not that valid without oil coating everything.
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ionbeam
2 FUN
I agree with what RaY said, and reaffirm that an engine shouldn't even be cranked without oil. I would like to add: If the engine does indeed have a blown cylinder head or cracked block the cylinder(s) involved will have dramatically different compression or leak-down rates from the others, with the engine hot or cold.
wmadoty
Well-known member
I would not crank the engine without oil. I would not have a problem Draining the coolant, changing the oil and filter, and running it long enough to fully prime the new filter and doing a compression test. My guess is you will notice compression problems even with the engine cold.
jeremyr62
Well-known member
It'll be fine. Engines will run with no oil for a surprisingly long time if they are not loaded. Google it.
I've done hot and cold compression tests and the results are broadly the same. Hot it maybe goes up about 5%.
I've done hot and cold compression tests and the results are broadly the same. Hot it maybe goes up about 5%.
ionbeam
2 FUN
But how long will it continue to have a functional life after that? The crank and valve plane bearings depend on a film of oil to float the journals, the crank and cams. Modern plane bearings are made to be 'self healing' to a point. They are able to embed small particles and not score the journals, but when the crank or cams bottom out on the plane bearings it scores them in a very life limiting way. Engines will appear to still run fine, but if you monitor oil pressure you will see that it never develops full pressure. If you do a tear-down and inspect the plane bearings you will find them to all be damaged. I'll not ever run an engine with plane bearings without oil, for any reason.
jeremyr62
Well-known member
It's his engine. He asked, I offered my opinion. I've done it with no apparent harm to engines. All I can say really. He's only talking about turning it over to get a compression reading after all. I really doubt the scenario you portray will come to pass in that short number of revolutions.
dcarver
Well-known member
Thanks to all for good responses! :yahoo:
Given I know it has water intrusion, Woofoo's response seems a best fit to my way of thinking, now that I'm thinking.. :huh:
Oil is cheap, the bike is going to sit for well over a month with no fire in the jugs. Bought 5 quarts of inexpensive Havoline oil on sale at O-Reilley's. Will see if I can find coolant drain (hopefully accessible w/o pulling plastic?) fill cc with oil then spin the motor just for the hell of it hoping to spread good oil about the lower and upper internals. Might even pull the plugs and fog the cylinders too.
FJRay
Well-known member
The sooner you get clean oil in it the better. Antifreeze is hell on engine bearings.
TomInPA
Well-known member
The coolant drain is easily accessible at the 6:00 position where the hose hooks into the engine on the bottom right of the bike below the clutch cover (8-mm bolt and copper washer). The cooling system has some vacuum and it will drain very slowly unless you loosen or remove the cap under the top-left cover. I use a 5-gallon bucket and tilt it against the clutch cover so it catches the coolant that falls by gravity, and intercepts the horizontal stream that shoots out when you remove the cap. LOL :lol:
dcarver
Well-known member
At home sick today but will head to shop right now. My gal needs help!
Very good, thanks Tom!
Back in a bit
SkooterG
Purveyor of Crooked Facts
150,000 miles and you don't know where the coolant drain is? Tsk! Tsk! 
beemerdons
Certifiable Old Fart
Kick his ass, Skooty!150,000 miles and you don't know where the coolant drain is? Tsk! Tsk!
dcarver
Well-known member
Fixed it for yah Don!Lick his ass, Skooty!150,000 miles and you don't know where the coolant drain is? Tsk! Tsk!
Never had to change or drain it myself, Skootie! I have a wonderful independent tech who doesn't charge $650 for a valve adjust.. so I've had him replace with new DI water/quality coolant/wetter each more often than called for valve check. For us who ride a lot, valve checks come often enough the fluid is still fresh and good when changed.
Oh, and this coming from Mr. SkooterG?
- Who needs to grease steering head bearings? The factory knows best!
- You changed *that* tire? It's still good for 7,435.3 miles!
- Changing rear-end oil is a waste of time and money?
- Don't make me drag out that pix of you and your gay Harley again, jes' sayin'!
Hugs n' Kisses!
SkooterG
Purveyor of Crooked Facts
226,000 miles ya bastage. That's what I can get out of an FJR without catastrophic damage and 'Oh, the DRAMA' you seem to incur on a regular basis.
No hugs, no kisses, just.........
:finger:
No hugs, no kisses, just.........
:finger:
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dcarver
Well-known member
Jeesh, that's harsh, :huh: Flipper! :rofl:
Yah know, if you wouldn't crash them bikes maybe you could more miles out of them!
..and no hugs, no kisses?
You've left me for Fairlaner? :wub:
