enginearin
|
| posted on 5/10/12 at 10:09 AM |
|
|
Compression test on engine out of bike
Hello All,
Further to recent gearbox woes i have sourced a new CBR1000RR engine. It's out of the bike already and, although it has traceable service
history, i want to check it over as fully as possible before handing over the cash.
Could someone please advise the best way to perform a compression test? I was planning on turning over the engine with the plugs out via the bolt used
to rotate engine during a cam timing check (under the round cover on clutch side of engine).
Are there any issues with doing this by hand using a ratchet?
Would it be better to use my electric drill or impact driver to turn the engine over?
Should i ignore both of those ideas and wire the starter to a battery instead (obviously there will be no fuse inline though)?
Any other thoughts on what i should / could be checking? I might be able to borrow a fibre optic inspection camera, but i don't really know what
i'm looking for... excessive carbon deposits? scratches to the bores? holes in the piston?
Any advice greatly appreciated
Thanks
Tim
|
|
|
|
|
snapper
|
| posted on 5/10/12 at 10:22 AM |
|
|
You won't get a true compression reading
I crank on the starter,plugs out, WOT, several turns until the guage stops moving up.
Doing it by hand slowly will leak compression until all valves are closed, when an engine turns fast the compression starts to build 50 thou before
the valve is fully closed.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
|
|
|
designer
|
| posted on 5/10/12 at 10:24 AM |
|
|
You will have to power up the starter motor and spin the engine to get a proper reading.
|
|
|
enginearin
|
| posted on 5/10/12 at 10:40 AM |
|
|
Thanks for the quick replies.
Daft question now... if he has drained the oil, presumably i need to refill prior to compression testing with a battery, or will there be enough oil
floating about to do the short test bursts without damaging the engine?
Also to save messing about with WOT could i just pull off the throttle bodies instead? I suspect that i'll need both hands for fiddling with
battery cables.
|
|
|
designer
|
| posted on 5/10/12 at 11:10 AM |
|
|
There should be enough there to stand a few second spin on the starter.
|
|
|
adithorp
|
| posted on 5/10/12 at 11:25 AM |
|
|
quote:
Originally posted by designer
There should be enough there to stand a few second spin on the starter.
There should... but if I was the seller wouldn't be too happy. DON'T DO THIS untill you've paid for it and if you bleep it up
it's your problem! On top of that, you'll empty the oil pump of oil and it can be a pain to get it primed again.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
enginearin
|
| posted on 5/10/12 at 11:35 AM |
|
|
quote:
Originally posted by adithorp
quote:
Originally posted by designer
There should be enough there to stand a few second spin on the starter.
There should... but if I was the seller wouldn't be too happy. DON'T DO THIS untill you've paid for it and if you bleep it up
it's your problem! On top of that, you'll empty the oil pump of oil and it can be a pain to get it primed again.
Hmmm... for the sake of £30 worth of oil, i think i'll take the four litres i've got in the garage with me.
Thanks again
|
|
|
BenB
|
| posted on 5/10/12 at 12:02 PM |
|
|
Presumably a leak-down test is out of the question?
|
|
|
enginearin
|
| posted on 5/10/12 at 12:57 PM |
|
|
quote:
Originally posted by BenB
Presumably a leak-down test is out of the question?
Don't think i have the kit for that... i've borrowed a compression tester from a friend.
What's required for the leakdown test?
|
|
|
BenB
|
| posted on 5/10/12 at 01:57 PM |
|
|
A leak-down tester and a compressor (or a supply of compressed air).... you can get low pressure leak-down testers which I suppose it would be
possible to jury-rig some kind of lash up using a spare tyre as a pressure resevoir but don't hold me to that!
|
|
|
BenB
|
| posted on 5/10/12 at 01:59 PM |
|
|
If you use a low pressure kit it will also be easier to lock the output shaft. 100PSI down the cylinder might make it a tad tricky when it's out
of the bike.
|
|
|
enginearin
|
| posted on 5/10/12 at 02:16 PM |
|
|
quote:
Originally posted by BenB
If you use a low pressure kit it will also be easier to lock the output shaft. 100PSI down the cylinder might make it a tad tricky when it's out
of the bike.
Thanks for the info, however i think this is a bit beyond my capabilities and the equipment i have available.
Anyone near Dorchester, Dorset have a low pressure leak down tester, know what they are doing with it and fancy helping me out about 5pm on Sat 
|
|
|
