D.I.Y. Cam Chain Replacement

Discussion in 'Parallel Universe' started by Dieselboy, Sep 22, 2011.

  1. TheJoker

    TheJoker Adventurer

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  2. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    I know that the says so. And I also now that they somewhere explained that the sump on the bottom is not a sump but a reservoir placed under the engine for better cooling. I can agree that F800 has separated crankcase and the pump is sucking out the oil from the crankcase but not to fill in the oil reservoir but to lubricate gearbox. So it is not a traditional wet sump lubrication system, more like first stage is a dry sump lubrication, second wet sump lubrication. F650 single have dry sump lubrication where oil was pumped into frame. The same in Yamaha MT-01.
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  3. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    It's been a long time since I read that thread...

    I'm lost on this part:
    "Heres how you check: First remove the timing chain tensioner so that the tensioner will not deploy further as removed, then remove the tensioner. Once removed, pull on the tensioner. If the tensioner is on its last notch of adjustment (or within 2 notches) the cam chain has stretched excessively."

    I think he is talking about removing the tensioner and then installing the mythical measuring tool?
    My tensioner does not have notches....
  4. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    Mine too.
    There is no easy way to test how much the timing chain has stretched.
    Theoretically it can be done but it is very tricky.
    The best way to check the slack of the timing chain is to set the BDP on 1'th cylinder ( still both valves closed). Than move another 10-20 degrees and hold when exhaust valve od the 1'th cylinder start to open. Than can remove the tenisoner cup can push the tensioner note how deep it went in (using some push-rode ore something) . This value should be compared with the same procedure done on non stretched timing chain.

    It is not a god idea to turn the engine without the tenionser plugged in. It can lead to some damage of the engine due to misalignment of the valves.
  5. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    The way the mythical BMW tool was explained ...
    It would measure the "composite" / total wear in the chain + guides.
    This would be a close approximate, and if we could find the damn tool ... easy to do... but ...................
    the damn tool can't be found ............. :dunno
  6. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    Ok finally some free time.
    I removed my tensioner and I discovered at least two major flaws. But about that later.
    First some photos of the disassembled tensioner.

    1. Full set.
    IMG_20181227_175302.jpg

    2. Outer piston (shell) from the chain side.
    IMG_20181227_175346.jpg

    3.Outer piston from the nut side. Sealing inner surface is clearly visible.
    IMG_20181227_175338.jpg

    4. Inner piston with lock ring and one-way ball valve.
    IMG_20181227_175453.jpg
  7. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    5. Lock ting
    IMG_20181227_175716.jpg

    6. The one-way ball valve from the inside of the inner piston.
    IMG_20181227_175511.jpg

    7. Inner piston on the nut.
    IMG_20181227_175558.jpg

    I have not attach any springs photos since are generally not that relevant for the general functioning.
  8. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    As you can see this is the new design of the tensioner. They improve the nut and the inner piston.
    Generally it is a very good design. It should last for at least 100k km easily without any excessive wear signs. So as the cam chain.
    But the manufacturer made a two terrible mistakes.
    First off all, the inner sealing surface is to small. It is about 5mm. It should be at least twice as that or even better have full length of the outer piston insides.
    And than the most crucial part of the hole system. The dimension. The inner sealing surface of the outer piston have ( in my case) 10.90mm and the inner piston outer surface in 10.75mm.
    That leads to leaking of oil.



    The hole inner piston is wobbling. This tensioner will newer work as it should.

    At the beginning I though it is caused by the wear of the elements but after careful measurement it turned that I have about 0.025mm of wear on the inner piston ( no visible signs).

    I made a simple drawing how this tensioner should work.

    8. Tensioner work-flow looking from the top (from the cam shafts side).
    Napinacz 1.jpg

    For the clarity of the drawing i skipped the springs once again.

    Throu the inlet nozzle oil is pumped to the chamber 1 and from there into the outlet nozzle (not on the drawing) and into the chamber 2.
    If the oil pressure in the chamber 3 is lower than in chamber 2, pressurized oil is flowing through the one-way ball valve into chamber 3.
    If the tensioner has no tension on the chain the chamber 3 will expand by pushing out the outer piston until it reach the chain and stop. Than the pressure in chamber 3 will rise until it will be the same in all chambers 1, 2, 3.
    This going to be our steady state.

    Situation 1.
    Now lets assume that the pressure of oil in chamber 1 will be constant ( engine is running).
    The only force that can interact in the system will come from the chain (from the left to right) on the outer face of the outer piston.
    In that situation pressure in chamber 3 will rise and it will be higher than on chamber 2 and 1. That difference (and the spring in the one-way ball valve) will close the one-way ball valve so the oil will not escape from chamber 3.
    So the outer piston should not move back no matter what force the cam chain will exerts on the face of the outer piston. The chain will be always tight.

    Situation 2.
    Now lets assume that the pressure of oil in chamber 1 will decrease ( engine is turned off).
    The chain will still pressing on the outer face of the outer piston. Pressure of oil in chamber 1 will be very low so as in chamber 2.
    But since the one-way ball valve is closed the pressure in chamber 3 will remain the same so the outer piston will not move back and cam chain will remain tight.


    That is the way how this hydraulic tensioner should work.
    So why it is not working this way?
    Because of the leakage.

    9. Leaking tensioner.
    Napinacz 2.jpg

    Since the sealing surface is small and the gap between the inner and outer piston is huge any excessive force on the outer face of the outer piston (cam chain) will cause a leakage of oil (red arrow) from chamber 3 to chamber 1.
    That will lead to move back the outer piston. That will also lead to excessive wear of the tensioner and the cam chain.

    The Remedy.

    Chamber 3 should be as sealed as possibile. The gap between the inner and outer piston should be no more than 0.025mm and all the surface should be highly polished. Than the viscosity of oil will seal the chamber and keep the pressure in chamber 3 for days.

    There are few possibile ways how to deal with the problem.
    1. Extended the sealing surface. BMW did it partially in the second generation of this tensioner. First gen had the same small sealing surface on the inner piston as it is on the outer one. That and the bigger movement of the inner piston ( old nut had lower height) caused massive oil leakage and losing cam chain tension. That is why BMW did change the tensioner first (during the warranty clams).
    2. However the best way to deal with the problem is t making the precise tensioner ( no more than 0.025mm) and longer sealing surface at the same tame.
    Why BMW did not do the trick?
    Because it is bloody expensive!!!
    Tensioner made ot of hard, polished steed with the precision of less than 0.025mm on the sealing surface 20mm long will cost about 500-700$ each.

    However I am implementing much cheaper method to seal chamber 3. Here in Poland should cost around 40$ and it can be used on the old tensioner as well.
    I will keep you posted about the results but bear in mind that it is a Christmas time and it can take up to 3 weeks.

    P.S.
    The reason why I have not mentions about the springs is that in the ideal situation they are not needed at all. They only keep the parts in more-less ok position and help with the first start (after the new tensioner has been installed or after a number of days without the run). In normal every-day life they have minimum impact on the tensioner. In our ( leaking tensioner and stretched cam chain) case they are very important. How important? I will describe it next time.
    Cheers,
    Chris

    P.S. 2
    Sorry for my English. Still learning.
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  9. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Thanks Chris!
    Your English is much better than my Polish... and my Spanish ;-)
    I'm looking forward to hearing about your $40 upgrade! :beer
  10. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Chris & all:

    two thoughts I had last night over a beer:

    1) is it possible BMW intentionally designed the device to leak so as to offer some "compliance" to the assembly?
    (and save money)?
    there was a conversation here on ADVRider a while back where in one opinion was that having a mechanical tensioner that was set
    and offered no "give" would be a bad idea and would cause high stress in the chain system during some conditions.
    I personally don't know if this is true or not.
    the old Honda engines I worked on had a "mechanical" adjustment, but there was some give in the system due to the bow of the spring steel tensioner which was covered with some teflon like wear surface. There was a service interval at which you were supposed to readjust the the tensioner to take up wear in the system. (I'm talking about 1970's type designs here... ;-)

    2) Is there much difference between the function of our tensioner and that of a hydraulic lifter found in the valve train of many cars?
    I replaced a set of lifters a few years back and was surprised to find I could purchase them for about $10 each...
    I was expecting to pay much more given my perception of the precision ground parts inside these units.
  11. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    1) I do not think that BMW intentionally designed our tensioner to have such a huge leak. Hawing no "give" will definitely have no bad influence on chain. Furthermore, less jerking in the system should prolong cam chain life. Any give will result jerking. This is why bikes with more hay-way riding have more mileage on the clock with the same cam chain problems than this with a city use (like mine). Lower RPM, more jerking. Lower oil pressure, more jerking.
    By the way, what some condition are we talking about? It is quite important.
    Besides, with our home made methods there is no possible way to seal the inner piston to be completely leak free so there will always be some "give".
    Manual adjustment of the tension is possible but we have to remember that most of the manual adjusters (like this: https://www.ebay.ie/itm/BMW-F700GS-...N-TENSIONER-/292846753817?hash=item442f06d819) is a bad design. I did not have any in my hands but judging from the drawing there is no sealing between the oil inlet/outlet and the crank case which results that most of the oil will not go to cam's oil rails. But once again I did not had one in my hands and on the ad they did not say anything about the design.
    There is also another issue. How do we now that the adjusted tension is good or bad. Maybe it is to tight or to loos. There is no hard knowledge.

    2) Not there is generally much no difference in terms of the idee. But it is in scale and in sealing. Most of the hydraulic lifter have some Teflon-like surface to seal the inner piston. But not all of them. Both of them have those one-way ball valves.
    However there is also another difference. Dimensions. Generally hydraulic lifter have no more than 6mm in diameter (to keep the mass low) and maximum of working length ( the value of play which it have to eliminate) is very small (no more than 0.5mm) In our case it is sometimes 4mm. So that makes the hole process lot cheaper.
  12. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Thanks for your kind reply @Wacholek

    The old Honda design used a tensioner spring to set the tension so it was pretty easy to do correctly.
    Like you I have no confidence in the simple mechanical designs are a good option.

    Keep us posted on your modification experiments.
  13. Zoef zoef

    Zoef zoef Long timer

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    I believe some leakage is intended, to ensure oil is often enough renewed. As long as oil flow in is same as oil flow out, after start, all is ok for me.
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  14. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    Some, maybe. However, hydraulic lifter are very much sealed. Oil change is done during normal work of the engine not when the engine is off.
    In our case should be the same. Like I said before there is no way to make our tensioner sealed enough to not have any leakage. So oil change will be provided.
  15. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    The news.
    I still waiting for my prototype part for my new tensioner. In the meantime I did some test at home.
    First of all I did measured again all the parts. There where some errors during past measurements so I have used very precise equipment this time.
    Besides I got almost new 5k km tensioner to compare wear.
    The Results.

    1) 5k tensioner.
    - Outer diameter of outer piston: 14.01mm.
    - Inner diameter of outer piston: 10.90mm.
    - Outer diameter of inner piston: 10.73mm

    2) 27k tensioner.
    - Outer diameter of outer piston: 14.01mm.
    - Inner diameter of outer piston: 10.90mm.
    - Outer diameter of inner piston: 10.72mm.

    So, there is almost no difference.

    I also made a test inner piston using brass. Diameter 10.80mm so with quite a big gap.
    Surface was dry but not flashed with petrol so there where some oil residue.



    By the way, I disassemble a new car hydraulic lifter. Difference between inner and outer piston was 0.05mm and have sealing surface about 12mm long. Very nice sealing.
  16. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Nice testing!

    So in the BMW assby the clearance is ~0.17mm or for us Americans 0.0067"
    As you said ... that's a LOT of clearance ... is BMW just being cheap?
  17. Wacholek

    Wacholek IN SEARCH OF PERFECTION.....

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    We have to remember that those engines where not made by BMW but by Rotax. Who took the blame for the first bad design of the inner piston? We would probably never know that.
    Probably that was a Rotax bad design. Why it was not repaired properly?
    There is more questions than answers in this matter.

    You have to remember that those chain tensioners are not universal. I has been used only in F800 family engine. I have no idea why BMW/Rotax did not used the same tensioner in all of BMW bikes. I did not heard about the problems with this part in F650 singles.
    Ordinary hydraulic lifter is produced in huge volume compared to our chain tensioner and that makes it much cheaper.
  18. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Thanks Wacholek!

    Yes of course it was a Rotax design.... so not truly BMW's fault in the beginning.

    i'll be watching your progress with interest!

    Jim
  19. michalkow

    michalkow n00b

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    Hi, it’s my first post here. I just did the change with DID’s open chain. As I look on this now I think it wasn’t so bad :) A couple problems, but now it’s looking good. Probably I will try to start engine on Sunday. Wish me luck :)
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  20. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    "Open Chain" .... sorry to be dumb (I'm still on my first coffee of the day :lol3)
    What is open chain?