What is needed to beef up the bottom end bearings etc.in Chinese motors

Discussion in '2-Stroke Engines' started by JVROOM, Oct 11, 2012.


    JVROOM Member

    Hi, I tried to post and it crashed sorry, question I've seen some discussion realize these Chinese motors, leave a lot to be desired and I know happy.

    What do I need to do to strengthen the crank assembly? Been working on this a long time and don't want to blow it up now. Thank you for all of your help and consideration.
    Sincerely, John :confused::bowdown::bowdown::bowdown:

  2. Fabian

    Fabian Well-Known Member

    Nothing is needed to beef up the bottom end on Chinese bicycle engines if they are fitted with the crowded roller big end connecting rod bearing.

    Having said that, nothing will stop them blowing up in standard condition if you keep revving them past 5,000 rpm, of which you should be getting a Morini engine if wishing to have a high rpm screamer.
  3. sp454e

    sp454e Member

    recommend bearings 6202.2rsr.c3 these bearing will elimenate alot of the vibration
  4. Fabian

    Fabian Well-Known Member

    What is the technical specification of these bearings ( 6202.2rsr.c3 ) and how do they compare to the standard bearing?
  5. sp454e

    sp454e Member

    on the tech side the bottom end are made loose. you will have lots of vibration from the bearing. the new bearings are made with a closer talorance for less vibration and little more on the rpm. I used to work in a machine shop. A tech rep that repairs the machines told me about this, when I Q. on chattering and vibration on the machines
  6. HeadSmess

    HeadSmess Well-Known Member

    looser bearings

    2rsr means its sealed on both sides. rip out the seal on the inside of each for crank bearings! leave the outer one as a supplement to the cruddy stock crank seals.

    c3.... now this is a tolerance reference. the clearance between the balls and the races.

    the first tolerance, c2, ranges from no clearance to a tiny bit of clearance.

    great for shafts that arent tight, and bores also a lil loose. and low temperature changes.

    cn or standard bearings have a wee lil bit of clearance to just a whisker more clearance. good for a shaft that needs a bit of effort to get on the bearing, or in the bore(not both!). good for some temperature.

    c3 even looser than cn. the shafts tight, the bores tight, and it gets hot.

    c4 looser still for when it gets even hotter and things expand even more! and your using shrinkfits and presses to get them on!

    c5 etc....

    the other tolerance is the abec number and usually abec 3 or 5 is whats readily available... 1 being pretty lousy, 7(or higher?) being super expensive...

    cn is standard. get a standard set of nachi bearings. anythings better than the china ones.

    now if you meant the lil and big end bearings...meh. bushes are best for some, rollers for others... never had any fail....