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Discussion Starter #1 (Edited)
POST 31K miles (50K KM) full engine check

ok after my engine did 50k KM on motul 7100, the crank needle bearing decided to die.
so guy have a taste of the full CBR 250 engine dissembly including full checks and expected engine components life spawn.

for now i posting the pictures and will post full measurements and calculations i a while

have a look on the inside feel free to ask anything
https://plus.google.com/photos/102273974749410979141/albums/5864527495782303249?authkey=CPjH2KrBobDhIg


here you can see the old piston and the new piston compared, you can clearly see that the molybdenum coating of the old piston is worn.
and the piston skirt coating is worn
 

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I'm surprised by the extent of the build up of oil deposits inside the engine... had you been using the Motul 7100 since the bike was relatively new, or did you switch to the synthetic oil more recently?

What was the typical operating RPM for your bike?... Cruising RPM?

Was the bike operated primarily for short rides, or for longer continuous distances?
 

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Discussion Starter #3
I'm surprised by the extent of the build up of oil deposits inside the engine... had you been using the Motul 7100 since the bike was relatively new, or did you switch to the synthetic oil more recently?

What was the typical operating RPM for your bike?... Cruising RPM?

Was the bike operated primarily for short rides, or for longer continuous distances?
the engine don't have any oil build ups it's just fresh oil which i didn't wipe before taking pictures, i serviced the bike at 48384KM the engine died at 49873KM

the engine did 1000KM on agip semi syntetic
6000KM on repsol syntetico
another 6000KM on repsol syntetico.(11K on repsol in total)
and the rest is motul 7100
the bike is mine since day 1
most of the time i was riding out of the city on twisted country roads.
most of the time the engine was working at 7000-8000 rpm
 

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You have driven an astonishing amount of kilometres since buying it. How old is this bike? 22 months? (your forum join date)
 

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I still don't like synthetic oil, in fact, now more than ever.
It does seem to work well in low rpm automobile applications, however.
But not in my bike!
Correct me if I'm wrong...

IR
 

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At what mileage was the first service done? Have you ever UNDER filled the oil level?
Surely these engines should be capable of a lot more mileage than this has done without damage.
 

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Discussion Starter #7
RED the bike is 14 month old

Island Rick
the oil looks very good all engine parts looks new, i have critical wear only on the piston skirt.
the crank died because of factory defect. so i will go for synthetics from now.
for low rpm applications synthetics almost the same as mineral oil the difference come at high rpm applications

DJSB
as i wrote: the first service was done at 1000KM
the engine was never ever ever under filled with oil
 

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Google tells me 7100 is a full synthetic.
engine lasted less than half a life.

now what have I been saying all along about what Honda recommends?
 

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So is it still under guarantee? If so, does Honda accept that it is a defect and are they willing to accept resonsibility. If they accept it's a defect why are you doing the repair yourself and not a dealer. I'm just worried that this is the NORMAL life of these engines. If It's a defect in manufacturing surely we all need to know about it unless it's a one off.

David.
 

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... the crank died because of factory defect...
How did you determine that this was a factory defect?

If it was the result of a factory defect, you would think that the needle bearing would have failed much earlier on, instead of surviving nearly 50,000 km's. Just saying that when it comes to an internal load bearing part like this, a defect due to material or workmanship will, more often than not, rear its ugly head much sooner than later.

Looking at the original piston, It would seem that the rings were not seated very well during the initial break in of the engine, allowing a significant amount of combustion blow by to occur over the course of 50,000 km. That amount of combustion blow by could then have lead to the excessive wear on the piston skirts. And all that material from the piston skirts has to go somewhere... into the oil, which would then carry that piston skirt material to the lower end crank bearings. Of course this is just a theory of why the needle bearing failed...

Not trying to start an argument here... just throwing other questions and possibilities out for consideration. ;)
 

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So is it still under guarantee? If so, does Honda accept that it is a defect and are they willing to accept resonsibility. If they accept it's a defect why are you doing the repair yourself and not a dealer... David.
If the bike was still under warranty, the OP has (by tearing apart the engine himself) by most standards pretty much eliminated the possibility for a warranty claim with Honda.
 

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So I suggested that synthetic oil works best at lower rpms, like in a car engine. You say at lower rpms it's similar to mineral oil, and that the differences show at higher rpms.
My point exactly. Your Honda lives at higher rpms, and self destructed way too soon using, guess what, synthetic oil.
I think from now on we should ask high mileage posters what type of oil they have been using. For now I remain a mineral loving guy!

IR
 

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RED the bike is 14 month old
Wow, not even a taxi would do that mileage! Did you sleep on it?

Someone else on these boards -tom- I think, rode the hell out of one and it only did 27,000km before the needle bearing in the cam/rocker failed.

I'm beginning to wonder how well built or otherwise these new engines are. I suppose this website, is provided by Honda for such real world feedback.
 

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Discussion Starter #14
ok you throwing lots of wrong statements before knowing whats going on,
the exact failure happened in 20 seconds.
the bearing separator which was cracked from factory caught in the rotating crank, the crank shredded the separator, all the needles got below the piston rode and this made the piston to hit cylinder head.
the piston deformed and rings stop moving. this is how the gases go in.

now about oil all engine components looks new including clutch.
its at 2.72 per friction disk and at 1.2 per spacer way more than service limit (2.27 disk , 0.15 spacer)
the piston pin is within spec.
the gear don't have any wear, the cylinder almost new.
the damaged parts is only the piston which deformed and the crank which bearing has broke.

if it was oil problem i would have excessive wear on every component, but i don't have any wear except the piston skirt.

i think honda did cheap piston(only 34$) and we paying the cheap price with low piston life.
it's sound awful that piston pin costs 40$ and live's more than the piston itself
 

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... the bearing separator which was cracked from factory...
So this needle bearing cage was cracked from the factory, since day one?... and was able to run trouble free for nearly 50,000 km before a sudden and complete failure? I'm finding that very hard to believe.

How did you come to the conclusion that the needle bearing cage was cracked before the bike ever left the factory?



... caught in the rotating crank, the crank shredded the separator, all the needles got below the piston rode and this made the piston to hit cylinder head.
the piston deformed and rings stop moving. this is how the gases go in...
The combustion gas blow by that is evident around the ring lands of your piston, did not just suddenly occur when the needle bearing failed etc...
As I said in my previous post, combustion blow by to that extent is typically caused by rings which did not seat to the cylinder adequately during the engine break in process.

How do you explain the excessive wear to the piston skirt?
 

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Discussion Starter #16
The new piston has very thin molybdenum coating, so thin layer can't last long.

About the bearing ,the needles absolutely not worn,the failure come from the cage only.
Before the failure the engine doesn't did any noises nothing was running like new.
I don't get where you saw lot's of gases going through?
The piston almost clean.
 

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I don't get where you saw lot's of gases going through?
The piston almost clean.
Those gases are the hot air in MotoMikes argument. His hobby horse is piston rings and he loves arguing about it. Don't get bogged down there.:p
 

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The new piston has very thin molybdenum coating, so thin layer can't last long.

About the bearing ,the needles absolutely not worn,the failure come from the cage only.
Before the failure the engine doesn't did any noises nothing was running like new.
I don't get where you saw lot's of gases going through?
The piston almost clean.
The needle bearing cage failed, I get that... you still haven't said how it is that you came to the conclusion that it was cracked from the day it rolled off the assembly line. Were you there at the factory when they assembled your crankshaft, and witnessed the engine builder install a needle bearing with a cracked cage?

What would you (feel free to chime in with your answer as well, Red) call that bronze/brown coating on the sides of the piston, in between the ring lands? Dried beef au jus?
It's called combustion gas blow by, and it's visible and plain as day in your opening post photo of the original piston (next to the new piston). Even Ray Charles and Stevie Wonder would be able to see that the piston rings were not seated properly.
 

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Be interesting to see if this is a common occurance as more cbr250's start to rack up more mileage. (or kilometer-age) Some have posed questions as to how long the 250 engine will last. If there is more dead bikes at ~50k km makes me glad to be selling my bike in ~6 months. Would also give me doubts about the durability of the new bargain basement 500's. And if dead 250's at 50k km becomes common and common knowledge that will be a negative when it comes to resale.

and yes this is just one bike out of thousands. but i would say most that have a 2011+ do not have 50k km yet. I am just coming up on 16k. If this year is as good as last year i be close to 30k by October.
 

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Having an old-fashioned shim under bucket Honda 250 engine with over 48k KM that has had frequent (every 2k KM) oil changes with Castrol GTX 10W-40 (yes auto oil), I'm hesitant to buy into this as an endemic problem with the "new" cbr250 engine. I know that the design changed to make the shims more accessible, but, you still need to get the rings seated during the break-in process.
 
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