Page 1 of 4 123 ... LastLast
Results 1 to 15 of 51

Thread: Big end banging

  1. #1
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31

    Big end banging

    https://youtu.be/CWBSJ8QFtLw


    This is my scooter's (BMW C1 with Rotax engine very similar to Leonardo) noise that is worrying me a lot. Strangely enough the knock is only audible at idle which is not expected from rod knock.
    Any ideas please?
    Mileage: 83.000 Km


    Thanks

  2. #2
    apriliaforum expert
    Join Date
    Apr 2011
    Location
    Clearwater, Fl
    Posts
    7,568
    I hear it through the entire rpm range. Time to check things out methodically before you blow the engine and throw the connecting rod through the engine block. You are going to have to tear it down and inspect the crankshaft and crankcase. If it has the same engine as a Leonardo then its a 125 which is severely under powered for a BMW C1 with the roof and all the automobile type comforts. The reliable bike was the Leonardo 250 which had the Yamaha Majesty VOG 250 engine.

    Like member TomD mentioned in the video comments you gotta stop that before you damage it beyond repair. That engine should not be started again until after its rebuilt or it can quickly become a total loss. Once repaired it will still be an under powered bike with a 125cc engine that really needs a 250cc.

    Note that the Chinese cloned the C1 and used a Honda GY6 to power it. It may be cheaper to look into transplanting a generic GY6 from China into that bike rather than spend a lot of money on repairing that 125.

  3. #3
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    I would like to test if possible before opening the engine if there is some rod bushings problem. Any idea how to do?
    By the way, when the engine is cold then I can't hear the banging sound but after some minutes the banging is very loud (makes the same sound like when a car has higher than normal gear in transmission and tries to drive uphill - this "trembling of the engine" weird sound).

  4. #4
    apriliaforum expert
    Join Date
    Apr 2011
    Location
    Clearwater, Fl
    Posts
    7,568
    TomD is the expert here on those engines however you may want to check the oil pump to ensure its not impacted by sludge or a weak bypass valve and that the oil filter is new with all seals in place along with the correct oil is being used. The timing chain may be a bit off so maybe some valve interference however I do not have high hopes on that one but you could start by also verifying that the valve tensioner, timing and clearance are also good.

    How long have you owned the bike and how many of those KM did you put on before this all started?

  5. #5
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    I have the bike secod hand. Bought it @ 10.000 km's. Now it has 83.000 km's.
    Recently I experiencec oil light flickering at idle (only with hot engine was flickering) but it stopped after I swapped oil pressure sensor AND fixed electrical problem that was not allowing the radiator fan to kick in.
    I will measure oil pressure and compare with my other (same model but younger) scooter.

  6. #6
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    Today I measured oil pressure on bike with problem AND on my second C1 which is much younger (20.000 km's).
    Surprisingly, both measured almost the same. I could expect some lower values from the one with 83.000 km's.
    In brief:
    Cold idle: Problematic bike starts with 0,8 and quickly climbs to 3,4 bar / Other bike starts at 0,5 and climbs quickly to 1,65. Strangely enough the older bike has higher oil pressure at cold idle.
    Warm Idle 77 degrees Celcius: Problematic bike settles around 1,65 bar / Other bike settles around 1,5 bar. Almost identical and above minimum limit.
    Warm @ 7000 rpm: Problematic bike around 3,65 bar / Other bike around 3,3 bar. Almost identical and above minimum limit.


    So in essense I can't notice any difference. Maybe you can explain it differently.
    By the way, the test with screwdriver shows no problem. I press hard and the piston doesn't move even a little.


    Random thought 1: Last thing I changed was a water pump. Maybe something wrong there (however it is a knocking sound - not pinging or rattling).
    Random thought 2: Higher rpm's don't worsen the knocking sound but make it smoother - when I drive eg at 70 kmh I swear the sound of the engine is the most melodic one, like perfect. This may mean that something frequency tuning may take place.
    Random thought 3: The temperature should be at least 60 degrees celcius before this banging sound starts. It's so strange that it sounds also melodic when I cold start it but when it reaches the 60 degrees then at traffic lights is annoying in a way like it speaks to me that it something is really bad.


    I now upload the video clips on youtube and will post later when they finish.
    Last edited by aware; 10-10-2018 at 10:33 AM.

  7. #7
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    Given the fact that this takes places @ temperatures higher than 50-60 degrees, I start suspecting debris formation leading to knocking.
    This engine should have compression of around 14 bar and recently has risen from 15 to 15.5 bars.
    What do you think?
    By the way revving up lowers substantially the knocking sound.

  8. #8
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    So until now basic conclusions: 1) it is not oil pressure related but temperature related (above around 50-60 degrees Celcius) 2) it diminishes gradually as rpm's increase. Go figure...

  9. #9
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    Lots of carbon residues.
    https://drive.google.com/file/d/1Kbq...w?usp=drivesdk


    https://drive.google.com/file/d/1nsh...w?usp=drivesdk


    https://drive.google.com/file/d/17-G...w?usp=drivesdk


    Darkest picture is "wet" piston after cranking it to measure compression.


    I need to clean and see if anything improves.
    Last edited by aware; 10-11-2018 at 09:42 AM.

  10. #10
    apriliaforum expert
    Join Date
    Apr 2011
    Location
    Clearwater, Fl
    Posts
    7,568
    Quote Originally Posted by aware View Post
    Today I measured oil pressure on bike with problem AND on my second C1 which is much younger (20.000 km's).
    Surprisingly, both measured almost the same. I could expect some lower values from the one with 83.000 km's.
    In brief:
    Cold idle: Problematic bike starts with 0,8 and quickly climbs to 3,4 bar / Other bike starts at 0,5 and climbs quickly to 1,65. Strangely enough the older bike has higher oil pressure at cold idle.
    Warm Idle 77 degrees Celcius: Problematic bike settles around 1,65 bar / Other bike settles around 1,5 bar. Almost identical and above minimum limit.
    Warm @ 7000 rpm: Problematic bike around 3,65 bar / Other bike around 3,3 bar. Almost identical and above minimum limit.


    So in essense I can't notice any difference. Maybe you can explain it differently.
    By the way, the test with screwdriver shows no problem. I press hard and the piston doesn't move even a little.


    Random thought 1: Last thing I changed was a water pump. Maybe something wrong there (however it is a knocking sound - not pinging or rattling).
    Random thought 2: Higher rpm's don't worsen the knocking sound but make it smoother - when I drive eg at 70 kmh I swear the sound of the engine is the most melodic one, like perfect. This may mean that something frequency tuning may take place.
    Random thought 3: The temperature should be at least 60 degrees celcius before this banging sound starts. It's so strange that it sounds also melodic when I cold start it but when it reaches the 60 degrees then at traffic lights is annoying in a way like it speaks to me that it something is really bad.


    I now upload the video clips on youtube and will post later when they finish.
    Could be a plugged oil gallery or maybe even a defective oil filter based on those reading. Oil has to make it to the bearings in order to do any good. Are you using the same oil and brand filter in both bikes?

    Did it overheat before you changed the water pump?

  11. #11
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    It had overheated some 20.000 km's ago.

  12. #12
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    Aha moment:
    One tooth off for both cam sprockets.
    Exhaust clearances very tight (0,11 vs minimum 0,20)
    Wrong timing probably brought quick wear of the valve seats.
    Rockynv mentioned about timing etc. Thank you so much.

  13. #13
    apriliaforum expert
    Join Date
    Apr 2011
    Location
    Clearwater, Fl
    Posts
    7,568
    Quote Originally Posted by aware View Post
    Aha moment:
    One tooth off for both cam sprockets.
    Exhaust clearances very tight (0,11 vs minimum 0,20)
    Wrong timing probably brought quick wear of the valve seats.
    Rockynv mentioned about timing etc. Thank you so much.
    Glad it was something simple and that you caught it before it became something worse. Do you have any idea why the timing chains jumped their sprockets?

  14. #14
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    https://drive.google.com/file/d/1eUM...w?usp=drivesdk

    No clue why it happened and still after retiming I wonder if the knock will be still there.

  15. #15
    apriliaforum prov-nov
    Join Date
    Oct 2018
    Location
    athens
    Posts
    31
    Another mystery is that the right sprocket if the chain jumped one tooth then the mark should be lower by one. Mine is higher.....

Page 1 of 4 123 ... LastLast

Similar Threads

  1. Flywheel nut /// Big End bearing
    By aprilakias in forum RS125 Euro-archive
    Replies: 5
    Last Post: 11-30-2006, 05:35 PM
  2. Big end bearing
    By joer1989 in forum RS125 Euro-archive
    Replies: 12
    Last Post: 10-08-2006, 08:46 AM
  3. big end bearings
    By philhansen in forum RS125 Euro-archive
    Replies: 5
    Last Post: 03-30-2005, 12:29 PM
  4. Big end/crank bearing removal
    By GavinR96 in forum RS125 Euro-archive
    Replies: 3
    Last Post: 02-20-2005, 09:19 PM
  5. big end
    By JakeRS125 in forum RS125 Euro-archive
    Replies: 2
    Last Post: 05-19-2004, 10:12 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •