IamTheMarcus
Young & Dumb
I've recently drained the oil from the bike, but I also obtained a compression gauge to test the compression. Should I put oil in her before attempting the compression test? Help is much appreciated.
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Do you need Oil in your Motorcycle to do a Compression Test?
- Thread starter IamTheMarcus
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- engine how to maintenance
If you just want to use the kick starter, then go ahead and do the test.
The compression test is best done on a warm/hot engine, so ideally the engine should be run before the test. I guess that means oil in the engine
Cold engine readings may be lower than when hot.
The compression test is best done on a warm/hot engine, so ideally the engine should be run before the test. I guess that means oil in the engine
Cold engine readings may be lower than when hot.
IamTheMarcus
Young & Dumb
I do have a electric start, can I use that?
Paulrxs650
XS650 Enthusiast
Yes, but if you want an accurate compression test you'll need a warm engine as RG says. Best to put the oil back in start, warm it up, then do the test with kick or electric
IMHO, I would not. Wait until you have oil in the engine.
alfredo
1978 xs650 Special
Yeah. I would put oil in the motor. In theory you don't need any else you have blow by on the pistons . . . . but metal on metal is NEVER good no matter how low the RPMs.
If you are talking a fresh rebuild then assembly lube the cylinders. If it's a motor thats been running recently (within a month or so) and you just drained the oil then you should be fine with a few turn overs. Otherwise always error on the side of caution.
If you are talking a fresh rebuild then assembly lube the cylinders. If it's a motor thats been running recently (within a month or so) and you just drained the oil then you should be fine with a few turn overs. Otherwise always error on the side of caution.
IamTheMarcus
Young & Dumb
Lubing the cylinders is just squirting a little oil into the spark plug hole isn't it?
Thanks for the help!
alfredo
1978 xs650 Special
If you are talking about a fresh rebuild/hone then I would say no in my personal opinion. I always give a good coverage skim of assembly lube on my cylinder walls with a lint free rag. Until the rings seat for good you don't need all that heat from dry metal.
If you are talking a used motor then . . . sure. Just make sure you use something that burns clean and do the spray when the cylinder is bottom dead center.
You should do the compression test to see what sort of reading you gert, If it is very low. Like well below 100 psi then do the wet test by adding a few squirts of oil in the cylinders. This helps determine if a low reading is the valves or the rings. If the compression comes up a large amount after you add oil then the low compression is a result of bad rings. If it doesn't come up much then it's the valves.
If the bike has set very long it may have low compression, like 100- 125 psi, both side close to the same, and just running it for a few hundred miles may bring the compression up to the 140-150 psi range.
If the bike runs, put in the oil and warm it up. Do the compression test as the engine is.
Then do it again with a few squirts of oil in each cylinder.
Report back what your readings are.
Leo
If the bike has set very long it may have low compression, like 100- 125 psi, both side close to the same, and just running it for a few hundred miles may bring the compression up to the 140-150 psi range.
If the bike runs, put in the oil and warm it up. Do the compression test as the engine is.
Then do it again with a few squirts of oil in each cylinder.
Report back what your readings are.
Leo
IamTheMarcus
Young & Dumb
Thanks for the help guys, still waiting on the oil filter and a few other parts from Mikes XS. I'll let you know if I have any other problems.
