Roller Bearing Failure Survey Thread

Discussion in '2-Stroke Engines' started by Skyliner70cc, Apr 28, 2008.

  1. Skyliner70cc

    Skyliner70cc Active Member

    Please list the following if you had a wrist pin roller bearing fail on you.

    Engine Seller (Boygofast, dax, powerking, kings, simpson, livefast etc..etc..)
    Engine speed/load at time of failure
    Miles on engine at time of failure
    Oil ratio
    Oil type (synthetic, conventional, castor, castor blended etc..)
    Does engine have lube holes drilled on the con rod area? Yes or no

    Please no discussion regarding this issue. This thread is for survey purposes. I never had a bushing engine fail on me..never had a bushing engine wear out on me when I used a castor blended 2 stroke engine. I'm thinking that the added complexity of a roller bearing is not improving reliability at all.

    BTW, I rode down the same hill at full throttle on a Dax engine (a bushing one) powered bike that I have abused over the past 2 years. Guess what, it did just fine but wasn't as smooth as the other engine that died.
    Last edited: Apr 28, 2008

  2. Skyliner70cc

    Skyliner70cc Active Member

    Boygofast engine
    Full throttle doing down a steep hill
    50 miles on engine
    At least 25:1 oil ratio
    Oil: Synthetic/castor blend
    No lube holes
  3. You may have something there. I mean if roller bearings are all that,how come automotive engines use bushings?
  4. BoltsMissing

    BoltsMissing Active Member

    Large Filipino
    Because they have a oil pump forcing oil.
  5. lennyob

    lennyob New Member

    Roller bearing failure

    I had this happen to one of the generic ebay type 70 CC kits. Don't remember the sellers name, but all these kits seem identical. I bought another kit from boygofast and it's identical to my first kit. At time of failure:

    - Engine had a few hundred miles
    - Speed about 15 MPH
    - non-synthetic oil
    - gas/oil ratio 24:1

    From the forums here, it seems this failure is common after a few hundred miles. I'm going to go the other way - that is, to replace the roller bearing on my new engine with a bushing, before this engine is destroyed also. Has anyone else done this on a new engine? Comments on how it worked out?
  6. spunout

    spunout Member

    this IS a discussion forum. not a survey-specific site. you can whine about this post if you like. we dont need anyone bullying the moddies, either.
    word of advice: let discussions go where they may, as long as they stay on-topic. the worst that can happen, is that you just might learn something useful.
    your first post in this thread, was full of things other than the bare minimum data, that you are demanding from us.
    Last edited: Apr 29, 2008
  7. Skyliner70cc

    Skyliner70cc Active Member

    If a person specified a survey and no discussion I would honor the request of the original poster. I can't recall how many times moderators in the past harped about keeping things on topic. The intent was to survey how frequent the bearing failure is occuring to see if it is a new problem. Dicussions regarding this topic/issue can be started on another posting.

    Its kinda funny and a little sad that the moderators themselves are the ones for not honoring my request.
    Last edited by a moderator: Apr 29, 2008
  8. thatsdax

    thatsdax Guest

    never ever go full throttle down a hill. ever.. If you do and your engine survived, consider yourself lucky...Thanks... enjoy the ride...
  9. Well there you go. THAT's why automotive bushings work. I mean they all even have an oil hole there.

    And I agree with DAX. That's why the Happy Time has a manual clutch. So you can pull that clutch lever when you're going down hill.

    My e-bay purchased Happy Time has a roller bearing. It has by now 2,000 miles on that puppy. I've taken it to full speed three times in it's entire life. And I ALWAYS clutch in when going down even a slight hill that keeps my bike rolling.

    But we've also seen bushings fail as well here. Same reasons it seems.
    Remember that guy with that seized engine and burnt out bushing from across the pond wanting a free engine from DAX?

    Remember the Happy Time. Be nice with it. Don't abuse it.

    Skyliner. Why on earth would you go down a steep hill at full throttle when you can go MUCH FASTER going down the same hill with the clutch in?
    Last edited by a moderator: Apr 29, 2008
  10. azbill

    azbill Active Member

    sounds like deliberately grenading a good engine...
    not even 'broken in yet'
    just to whine that it happened
  11. spunout

    spunout Member

    one of my motors is a Kingsmotorbikes (NOT Powerking. ppl get that confused) 70cc. 2years old, over 10,000miles, and STILL no bushing failure.
    other motor is a Dax w/roller bearing. unknown miles. no failure.
    i genuinely hope this helped in some way.

    EDIT: both motors have been run equally as hard. I'm NOT easy on them, by any means. since they're different in the bushing/bearing thing, i wonder if bushing/bearing failures are due not to design but to defect or slop in the part ITSELF.
    we know how "quality control" are just words of the past in China
    Last edited: Apr 30, 2008
  12. Jixz

    Jixz Member

    150 miles
    Going down a hill, open throttle..
    20 ish' :1
    synthetic oil

    Can I get some links to some 3rd party bearings, id like to try some more hight quality bearings with the repair..

    Repeat after me. Oh noes. I'm about to go down a big hill. It's time to PULL IN MY CLUTCH!!!!!

    That is my rant for the week.
    Thank you for letting me vent.
  14. Jixz

    Jixz Member

    :[ I Know.. Wish i had been told before. I'm just a speed demon, and only 15, cant get my Kawasaki ninja that i want o-so dearly
  15. hot70cc

    hot70cc Guest

    You better change your ways, cause you will be dead in a couple of years with that attitude,,,, Think first;)
  16. Wildman 1965

    Wildman 1965 Guest

    I have a chris hill 70cc i bought in August of last year,i rode it all winter here in ontario canada.I ride every day.The motor runs awsome and never had any problems with what so-ever with this motor!! Starts every time with no choke and goes like abat out of ****!! lol!! Chris has top quality bearings through-out his kits!! And would recommend to anyone that wants a quality kit!! I,m a very satisfied customer!! No bearing problems Here!!
  17. BoltsMissing

    BoltsMissing Active Member

    When I got my very first kit, it was obvious to those who have worked in mechanical repairs, to identify that metal is not just metal.
    There is not enough space and time to explain my version of how I know this and the same may apply to anyone else who has done or doing this type of work.
    The same in principle, I would not know how to identify a quailty hair dryer if I saw one,but a hairdresser would.

    So, having said this, take it for granted when we try to express a quality issue and why this occurs, it's basicly the fault of the consumer, that's what it comes down to.

    Let's say a HT is manufactured by 6 differant factories in China, and factory A insists on a very high standard of quality.
    Everything is finished to a fine art and it takes a day longer to do this. Plus the cost of quality parts adds another $200 to the price of the kit.

    Factory F (6th) does the cheapest price, it uses screws that "melt" like plasticine when you try to tighten or undo. The engine runs, but you have constant "silly" problems, such as roller bearings with no case hardening on the clutch pin.
    To upgrade this motor your self, it will cost you at the end the same as if you were to purchase from factory A, but it will take you months of trial and error.
    Factories B,C,D, and E have various levels of price and quality, so A and F are at either side of the scale.

    So, we have Kit A @ $500 and Kit F at $300
    We know Kit A is Quality +++
    and Kit F is Quality ---
    All 6 kits are from the exact same "blueprint" of the HT.

    You as the consumer on a budget and time restarints, meaning you cannot afford to be off the road, which kit will you settle for ?

    The $300 or the $500, when you already know to get a $300 kit up to specs. it will end up costing $500 anyway,
    only thing is you have to DIY.
  18. Fabian

    Fabian Well-Known Member

    Now here we have a person who is speaking with sound logic - people should listen to this guy and follow his instructions to the letter. I'll add my two cents worth too:

    Quote Large Filipino


    Repeat after me. Oh noes. I'm about to go down a big hill. It's time to PULL IN MY CLUTCH!!!!!

    Reply and advise in kind:

    A very quick tutorial on 2-stroke engines and their reciprocating load bearing requirements.
    - Any reciprocating engine will have two load transfer points to the connecting rod, either using plain metal shell bearings or roller bearings.
    Roller bearings are a requirement if the load bearing surface does not have pressurised lubrication, such as common 2-stroke engines.
    As the connecting rod moves about on the crankshaft and the piston gudgeon pin, swinging fore and aft the needle rollers attached to the bearing cage rotate clockwise and counter clockwise through 360 degrees of movement.
    It doesn't take much intelligence to understand that the needle roller have weight and a spinning object wants to keep spinning unless there is an opposing force applied to it.
    As the connecting rod moves backwards and forwards in relation to the crankshaft pin, it also moves the needle rollers clockwise and anti clockwise. Everything is looking good so far.
    Now you are travelling down a hill and, naturally, you want to go fast, so ovver revving the engine is the result.
    Ok, you've just played a healthy part, setting in motion the time for your engines destruction.
    Those little needle rollers have a speed rating. If exceeding the speed rating the needle rollers will try and keep spinning whilst the connecting rod is trying to reverse their rotation. Naturally the connecting rod will drag the needle roller cage around on the crankshaft pin and at some pint the needle roller will stop spinning and momentarilly be dragged accross the pins surface whilst stationary.
    This has the effect of wearing a very microscopic flat spot on the crome surface/hardened surface of the needle roller.
    As you keeping over revving the engine (outside the maximum specification of the needle roller bearing) more and more microscopic flat spots will occur on the needle roller surface.
    This happens in micro seconds and after 2 mins of excessive revs, the crome hardening will start to break up, exposing the softer base metal.

    Now you are well and truely on the way to bottom end bearing failure.

    As time passes and periods of over revving occur (typical of single speed setups) the needle roller starts to get flat spots on the softer base metal.
    Now you no longer have perfectly round needle rollers and as they rotate, they vibrate the heck out of the needle roller bearing cage, hammering out the reciever slots for the needle rollers.
    Another decent downhill run at this pint will have the needle rollers break out of the needle roller cage and all those needle rollers will fly about inside the engine, jambing themselves in between the bore and anywhere else they can find a suitable home, bringing the engine to a rattly stop at best and engine ceasure at worst.

    Please listen to Large Filipino when he says - DO NOT OVER REV YOUR ENGINE - PULL THE CLUTCH IN WHEN GOING DOWNHILL.

  19. Fabian

    Fabian Well-Known Member

    My other two cents worth

    To avoid over revving the engine whilst maintaining reasonable speed - GET YOURSELF A SickBikeParts Jackshaft Shifter Kit - your engine will thank you for it.

  20. Skyliner70cc

    Skyliner70cc Active Member

    Yep, with the jackshaft, I can go downhill at WOT all day long with no issues :)