Piston slap: How will it end? - BMW F800 Riders Forum & Registry



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  1. #1
    boraaski's Avatar
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    Probably made more noticeable by the recent and inevitable cold Minnesota weather, my 2007 F800ST (29,000 miles) is now showing signs of piston slap. It is worst in the morning @ startup getting much better after several minutes of warm up. Stethoscope observations indicate it is worst for the right hand cylinder and the timing chain region of the motor (LH side) is quiet.

    Here are my options:

    1. Rebuild the engine with new pistons and put up with the increased vibration one gets w/o having replaced the balancing rod. (…and possibly replace the balancing rod too? $$)

    2. Continue riding the bike in its "slapping" state until the engine gives up. At that time look for a used post-2008 engine with proper pistons and do an engine swap.

    3. Trade the bike in on a 2009 or newer F800 ST. Yup. I like the bike enough to stay with it. Additionally, I'd just move my farkles over to the new bike.

    4. Hybrid option: Keep the existing bike going for another 2+ years and then trade for a GT.

    Questions:

    1. Have I missed any options?

    2. How does a motor with piston slap eventually die? Does it grenade or putter out?

    3. How long are F800 engines exhibiting piston slap lasting these days? Any data?

    Thanks in advance!
    Kirk
    2013 F800 GT: Rostra Cruise Control, Pelican 1500 saddlebags, Stebel Nautilus Airhorn, Sigma 1609 speedometer 

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  3. #2
    Elgin, Scotland ST404 is offline Volunteer Moderator - GT
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    Kirk

    Have you approached BMW for a goodwill payment as the piston slap is a known issue.

    I think you will struggle to find data on how long the engine will last if left to it's own devices as most have already been repaired

  4. #3
    Zelhem, Netherlands de100kb is offline Volunteer Moderator - Global
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    The official BMW point of view is the engine will not fail catastrophically but will only get louder and louder until it's unbearable.

    As to your options: in your situation I would go for option 3 if I could afford it and 2 if the money's too tight for option 3 at the moment, but only if the dealer confirms it looks like piston-slap.

    For extra options: trading it in for a GT right now? Would be more expensive for the short run but it could be cheaper in the long run, especially if you value peace of mind.

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  6. #4
    N4HHE's Avatar
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    Have you ever removed the left side cover and updated the gasket? It leaks internally. If it leaks bad enough the low-oil light illuminates at idle. I suspect if it doesn't leak bad enough or your oil pressure sensor is more sensitive than some you won't get the indication. Yet there will be less oil and less pressure feeding the crankshaft, bearings, and cylinder walls.

    I think this gasket is a primary suspect in the "piston slap" issue. Yes, BMW/Rotax changed the design of the pistons but no design change of pistons can make up for the lack of oil. Believe this gasket changed at the same time as the magical piston redesign.
    2016 Yamaha FJR1300A; 2016 Beta 430RS; 2007 BMW F800S; 2009 Husaberg FE450; 2016 Subaru Outback; 2018 F150; 2013 Tesla Model S 85; 1983 Porsche 928S; 9 cats 

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  8. #5
    notacop is offline The original Schwartz Wald Troll
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    Golly, I shoulda kept my deer crashed bike and parted it our. 64.5K miles and as strong as the day it was new. Woulda been cheaper that farting with corporate BMW over a known problem they had with the first batch of 800's.
    Much luck getting this sorted out. Maybe the problem with a low mileage bike is they don't get worn until long past warranty.

  9. #6
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    Thanks for the feedback everyone.

    The bike was purchased used at a local BMW dealership 2 years ago and I haven't yet approached them with the problem. Honestly, as long as the outside air temp is 40 F (5 C) or above, the piston slap isn't noticable above the usual clatter the engine makes.

    David: I noticed the flickering oil light 2 years ago shortly after buying the bike and consequently replaced both the side cover gasket and the oil pressure sending unit. The old gasket was in perfect condition. Not sure if it was the gasket or the sending unit that was the problem but I haven't had a flicker since.

    Karim: As you suggest, peace of mind is very important but $$ matter too. I haven't sorted out just where to draw the line. Maybe what I need to do is test drive the GT at the local dealership for more information. (No good can come from this)
    2013 F800 GT: Rostra Cruise Control, Pelican 1500 saddlebags, Stebel Nautilus Airhorn, Sigma 1609 speedometer 

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  11. #7
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    You missed these options:

    1. Selling (rather than trading it in) it now
    2. Sourcing a s/h motor

    Neither of them easy choices for various reasons. Motors come up second hand and it wouldn't be too hard to swap it out, but you may have the same trouble again. A repair is fiddly and costly and may have vibes as you suggest.

    Having had a model with what I strongly suspected was the dreaded slap, I mulled it all over as you have and ultimately sold the bike. I sold it cheap, well below market value that would have left room for the new owner to replace the motor s/h and still not be out of pocket. I took the view that I'd had my money's worth out of it in fun and saved fares.

    I bought a well priced late 800s model s/h with a nice quiet motor and am so much happier with it. I could never get over the clacking noise, despite ear plugs and a pipe!

    So why not move on?

    Good luck with whatever route you take.

    BTW my bike was not overly sensitive to temperature in terms of noise levels. You absolutely sure is is the slap? Lots of owners just report noisy motors.

  12. #8
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    Quote Originally Posted by simclair View Post
    BTW my bike was not overly sensitive to temperature in terms of noise levels. You absolutely sure is is the slap? Lots of owners just report noisy motors.
    I agree, temperature sensitivity is unexpected. Points to something about the motor oil. Motor oil leads to suspect cam chain tensioner.
    2016 Yamaha FJR1300A; 2016 Beta 430RS; 2007 BMW F800S; 2009 Husaberg FE450; 2016 Subaru Outback; 2018 F150; 2013 Tesla Model S 85; 1983 Porsche 928S; 9 cats 

  13. #9
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    Quick update: I opted for peace of mind. Now I have the new 2013 GT to look at all winter long!
    2013 F800 GT: Rostra Cruise Control, Pelican 1500 saddlebags, Stebel Nautilus Airhorn, Sigma 1609 speedometer 

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  15. #10
    WildWilly's Avatar
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    Quote Originally Posted by boraaski View Post
    Now I have the new 2013 GT to look at all winter long!
    I forget, is winter in Minnesnowta 9 months or 10 months? What color tripped your peace of mind trigger? If it's white, tie a helium balloon to the handlebars. Easier to find in a snow bank. THINKING SPRING in Ioway!!!!!
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  16. #11
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    Quote Originally Posted by boraaski View Post
    Quick update: I opted for peace of mind. Now I have the new 2013 GT to look at all winter long!
    You have my sympathies. That must be painful. Will your wife let you keep it in the living room until spring? Replace your favorite chair. Sit on the bike while watching TV?
    2016 Yamaha FJR1300A; 2016 Beta 430RS; 2007 BMW F800S; 2009 Husaberg FE450; 2016 Subaru Outback; 2018 F150; 2013 Tesla Model S 85; 1983 Porsche 928S; 9 cats 

  17. #12
    Doghouse's Avatar
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    I also had increased 800st cold weather slapping noise on 2007 800st. Improved with gasket replacement and semi synthetic oil. I never thought it was piston slap. Similar if not colder riding weather 500 km north of you in Winnipeg.

  18. #13
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    I can't believe the piston slap debate is still going on. My 07 was so diagnosed in '10 @ 50k km. I ignored the advice to 'rebuild' the piston crank assembly but do oil\filter 8k km intervals instead. The bike is slapping merrily away with over 140k km on the clock. Im unsure what the machine will die of but slapping pistons dont appear to be a terminal disease. I have a '12 for distance touring but find the older st just as reliable.

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  20. #14
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    I've just had my piston slap sorted under warranty, and it turned out that I have no idea what piston slap sounds like as the bike still sounds exactly the same (to my untrained ear!).
    Apparently it's fixed, but the noise I thought was the piston slap still continues, and I think BMW told me it was the injectors(iirc?) I can hear????

    For what it's worth, and seeing what Bren has experienced, I wouldn't worry too much about it! Keep on top of the oil changes and all should be fine and dandy?!

  21. #15
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    Good for BMW in humouring dissatisfied customers. Even low end Asberger types buy F800's. Life a'int perfect. !!!

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  23. #16
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    Hello
    Bought a spare F800S engine for parts.
    Any guesses what has happened here...

    VIDEO: https://streamable.com/0uuton

    Click image for larger version. 

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  24. #17
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    Broken rings/bore wear?

  25. #18
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    Not the worst in my opinion, haven't got to the rings yet

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  26. #19
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    BMW asks for two different spark plugs in their service manuals iirc. So if yours looks like that - maybe a fuel issue? What did the oil look like?

  27. #20
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    Spark Plugs operational, oil deposits all over the spark plug tips.
    The oil looked normal, not that much drained out from the oil pan. This one was burning oil heavily.

  28. #21
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    THIS is how it will end.

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