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Thread: no compression at all either cylinder!

  1. #1

    no compression at all either cylinder!

    I just bought a 2002 BMW 1150 rtp with 110K miles. PO said he rode to work and home, next day it wouldn't start. Checked for spark good,, took off valve cover to see if valves were moving, good, and gave up. I trucked it home and after 2 days of work, I'm stumped. There is no compression in either cylinder. Verified with new gauge. I can feel air coming from valve cover area. I removed the left head and cylinder base, and they look fine, great really. I was expecting a hole the the piston or cylinder wall cracked or broken/stuck rings. But since both cylinders have no compression I can't see them both failing overnight anyway.
    So now it's disassembled and I have no clue why there is no compression. I was thinking of doing a leakdown test, but there is nothing to leak down.
    Any ideas would be appreciated.

  2. #2
    Liaison 20774's Avatar
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    Ed -

    Welcome the forum! Sorry it's under these circumstances. This seems like a real head scratcher. My first thought would have been timing chain/belt but you said the valves are working. Did the valves had the proper clearances? Rings would be next to hold compression. If the pistons aren't holed, it really seems odd.
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  3. #3

    Thanks

    Quote Originally Posted by 20774 View Post
    Ed -

    Welcome the forum! Sorry it's under these circumstances. This seems like a real head scratcher. My first thought would have been timing chain/belt but you said the valves are working. Did the valves had the proper clearances? Rings would be next to hold compression. If the pistons aren't holed, it really seems odd.
    The valves had some play on both intake and exhaust when closed, didn't measure. Yeah, it's quite odd. I've fixed many engines, even an old ford 8N tractor that had been sitting for 25 years had better compression (it runs now).

  4. #4
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    I'm not an expert on this at all...just remembering something I read and I'm really very vague about this. Isn't there something on a lot of newer motorcycle engines that releases the compression initially to make it easier for the starter motor to crank over? If that's true, that could be why you have no compression on either cylinder.

    Chris

    Here's a link to a Wikipedia article on it. https://en.wikipedia.org/wiki/Compression_release I think you're chasing the wrong thing by looking at the compression. I'd look at something more simple before tearing it down.
    Last edited by daboo; 05-22-2017 at 03:54 PM. Reason: Add link.
    Elnathan - 2014 BMW F800GT
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  5. #5

    compression release

    Quote Originally Posted by daboo View Post
    I'm not an expert on this at all...just remembering something I read and I'm really very vague about this. Isn't there something on a lot of newer motorcycle engines that releases the compression initially to make it easier for the starter motor to crank over? If that's true, that could be why you have no compression on either cylinder.

    Chris

    Here's a link to a Wikipedia article on it. https://en.wikipedia.org/wiki/Compression_release I think you're chasing the wrong thing by looking at the compression. I'd look at something more simple before tearing it down.
    Yes, my 1500 Intruder had one, it held open one valve during initial cranking. No such device on this bike.
    If it has no compression, nothing else matters, it won't run. Spark, timing and compression it all it takes to run an engine. Even if it's out of time, it will fart, backfire, something, but not without compression. Pour some gas on the ground and light it, it will burn but not explode unless you put it under pressure. Too late on the not tearing it down part. I thought long and hard before I took the head off, not much else to do.

  6. #6
    Registered User dieselyoda's Avatar
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    When you did the compression test, was the throttle wide open?
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case, my baby, fast, fun)
    3xR90/6, two just sold, one for a sidecar. 1983 K100RS (Cafe now)
    Very Rough R80RT. 1987 K1100RS (freaking hooped I think)

  7. #7
    Voni's R1100RS lost compression in both cylinders while riding in a heavy rainstorm. She had just ridden down an Interstate off ramp to go get fuel. At the stop sign the engine died. Water had entered the forward facing air snorkel and made its way into both cylinders. This caused carbon in the combustion chambers to break loose. At highway speed it blew past the valves but at idle, bits of carbon lodged under the exhaust valve heads causing the immediate loss of compression - both cylinders.

    So, could some such incident have caused carbon bits to break loose? What is the backstory here?
    Paul Glaves - "Big Bend", Texas U.S.A
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  8. #8
    Quote Originally Posted by daboo View Post
    I'm not an expert on this at all...just remembering something I read and I'm really very vague about this. Isn't there something on a lot of newer motorcycle engines that releases the compression initially to make it easier for the starter motor to crank over? If that's true, that could be why you have no compression on either cylinder.
    An R1150 does not have a compression release.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  9. #9

    leak down test on remaining intack cylinder good?

    OK, now I'm totally blown away. While waiting for suggestions, I pumped up the right cylinder to 100 psi, and it held! Yesterday I had no compression (even with the throttle held open. Does this mean both my compression gauges (one brand new) were faulty! I guess I'm going to reassemble it and go from there. I'm not doing too well so far on this "simple" project. I lost the cam chain tensioner piston (black plastic pushed by the spring) into the crankcase too. Maybe I can flush it out. Better get a new head gasket too. Does the cylinder base have no gasket, just sealant? That's a new one on me, but this BMW is a new one on me too.
    I have other motorcycles to ride and I'm retired. Why am I doing this again? Oh, for the satisfaction. I'm waiting for that.

  10. #10
    Quote Originally Posted by PGlaves View Post
    Voni's R1100RS lost compression in both cylinders while riding in a heavy rainstorm. She had just ridden down an Interstate off ramp to go get fuel. At the stop sign the engine died. Water had entered the forward facing air snorkel and made its way into both cylinders. This caused carbon in the combustion chambers to break loose. At highway speed it blew past the valves but at idle, bits of carbon lodged under the exhaust valve heads causing the immediate loss of compression - both cylinders.

    So, could some such incident have caused carbon bits to break loose? What is the backstory here?
    Hasn't rained in a month. So did it get fixed without a teardown, just curious.

  11. #11
    Registered User dieselyoda's Avatar
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    I have an R1100R in my shop as the owner was told he had poor compression on both cylinders. Bike ran like crap because the RH throttle cable was out of it's socket and the plugs for vacuum were badly cracked, split open.

    He was told compression was just 100 PSI.

    I warmed up the bike, pulled both spark plugs, compression test with throttle wide open, got 150 on both cylinders. Did cylinder leak down, less than 5%.

    ???

    Put bike back together, corrected all the little problems, checked balance, within 1.5"/hg. I'm happy now, owner happy now.

    As I've said before, keep to simple things first. A compression test will give you an indication that there is a problem but it won't tell you what the problem is.

    Cylinder leak down is the only way to get to the root and can even tell you that cam timing has gone bad if you do it right.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case, my baby, fast, fun)
    3xR90/6, two just sold, one for a sidecar. 1983 K100RS (Cafe now)
    Very Rough R80RT. 1987 K1100RS (freaking hooped I think)

  12. #12

    oops, forgot to remove schraeder valve

    My diy leakdown tester test was wrong. All I was testing was the pressure in the hose, because I forgot to remove the air valve on the part that screws into the spark plug hole. After this came to me, I repeated the test, and it won't hold enough pressure to get up to 10 psi. Sorry for the misinformation. No air was coming out of the intake or exhaust, exhaust manifold removed, intake FI side off too. OT mark showing in window hole, valves loose. Still stumped.

  13. #13
    Quote Originally Posted by edheiser View Post
    Hasn't rained in a month. So did it get fixed without a teardown, just curious.
    I had to remove both heads and manually clean the soggy carbon bits out of the exhaust tract.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  14. #14
    Registered User dieselyoda's Avatar
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    Quote Originally Posted by edheiser View Post
    My diy leakdown tester test was wrong. All I was testing was the pressure in the hose, because I forgot to remove the air valve on the part that screws into the spark plug hole. After this came to me, I repeated the test, and it won't hold enough pressure to get up to 10 psi. Sorry for the misinformation. No air was coming out of the intake or exhaust, exhaust manifold removed, intake FI side off too. OT mark showing in window hole, valves loose. Still stumped.
    Ok, I think I'm reading this right, maybe. You put, say 100 PSI into the cylinder while at TDC of compression/combustion stroke, valves are closed, push rods loose, and it doesn't hold 10 PSI but no air coming from intake or exhaust side of head? The piston can't move, right? You are in 5th gear and rear brake locked solid?

    The air has to go somewhere..........

    If not out the exhaust or intake, take the oil fill cap off and if the air is coming from there, that be bad.

    To get further using a cylinder leak down, you bring your pistons to 45 degrees of stroke on compression, try again. If you still can't hold air, there is a hole in the piston. If it holds some air, start bringing piston towards TDC on compression and if the air leak gets worse, you have bad rings/tapered cylinder bore.

    I should add that you need an air volume of at least 6 CFM as the volume and pressure are needed to make sure the rings are expanded. A bicycle tire pump will just make you confused and frustrated.

    I won't go into confirming that cam timing is your issue at this point because I think your issue is procedural.

    You are welcome to PM me if you need.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case, my baby, fast, fun)
    3xR90/6, two just sold, one for a sidecar. 1983 K100RS (Cafe now)
    Very Rough R80RT. 1987 K1100RS (freaking hooped I think)

  15. #15
    OK, this is the best info so far, thanks!
    You are right, my problem is my little pump and my DIY leak down tester, and I am confused and frustrated! So last night, I got a new leak down tester with 2 gauges, and a 10 gal compressor (I needed a new one anyway since mine quit working). I will try again as soon as I get the correct hose fittings for the hose, I would have thought they came with the new compressor and hose, but no. Of course I gave my old ones away to the scrap guy.
    I am working with one un torn down cylinder since the other is still torn down. Should I reassemble it first, I'd have to use the old head gasket for now, or just test it as is since both cylinders were at no compression.
    Perhaps it is cam timing, that would explain no compression when cranking (valves open at wrong time), I haven't even taken off the front cover yet. Perhaps you can tell me what to look for. This Haynes manual has crappy photos. I also could use a good photo of the cam chain gear (in head) to get it back on correctly.
    Thanks again!











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