Roller Bearing Failure Survey Thread


Active Member
Local time
7:47 PM
Nov 17, 2007
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.
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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
You may have something there. I mean if roller bearings are all that,how come automotive engines use bushings?
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?
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.
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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.
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never ever go full throttle down a hill. ever.. If you do and your engine survived, consider yourself lucky...Thanks... enjoy the ride...
Large Filipino

Because they have a oil pump forcing oil.

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?
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