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POST 50K KM full engine check

55K views 197 replies 37 participants last post by  Dalap 
#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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#2 ·
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?
 
#3 ·
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
 
#6 ·
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.
 
#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
 
#10 · (Edited)
... 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. ;)
 
#8 ·
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?
 
#9 ·
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.
 
#11 ·
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.
 
#12 ·
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
 
#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
 
#15 ·
... 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?
 
#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.
 
#19 ·
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.
 
#20 ·
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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#21 · (Edited)
To MotoMike
I agree that worn rings are needed to allow that residue build up, but it is just one photo on a website. We are not in a garage and we don't have the full picture.

That is to say, this motorcycle is not typical. It has done 50,000 km in 14 months. We don't know anything about it apart from a few scant facts and one photo, which gives little ground to make any generalizations about this engine. I just don't know enough about it.

To me is it just a small piece of data to make a mental about. These are new engines. We don't how many birthdays they are going to have. The data is still coming in.
 
#23 ·
I Just emailed the Honda Dealer here in South Africa.

They Use Semi-Synthetic oil for the Break-in process.
As you stated in the beginning of the thread you also had Semi-Synthetic for your break-in period.

Out of every single thread I've read about, the break-in period says NO to any type of Synthetic Oil.

Maybe because the use of synthetic oil made the Rings Seated incorrectly causing the rings to wearing incorrectly cause the oval shape. Meaning there was blow back. making the oil in the Long run degrade Quickly.

To many variables to know exactly what went wrong.
 
#24 ·
There were no oil degradation, the oil alwas were clean.
Again the gases blown by on 2 sides after the rings sized .
If the rings wouldn't set from day one I would have lots of ash and deposits in every oil change.
And I alway got clean oil except the last oil which I drained before disassembling the engine
 
#26 · (Edited)
Yep and the most intresting is the shredded copper cage and how it hapen?
The cage shredded, the the needles got broken into pieces, and all the needles going below the crank, thepiston to cylinder head Clarence decrease and piston hits the cylinder head.
The piston deformed this coused the rings to size. And this coused the gasses to blow to the oil


That's the chronological order of events
 
#27 ·
Yep and the most intresting is the shredded copper cage.
The cage shredded, the the needles got broken into pieces, and all the needles going below the crank, thepiston to cylinder head Clarence decrease and piston hits the cylinder head.
The piston deformed this coused the rings to size. And this coused the gasses to blow to the oil


That's the chronological order of events
I have to disagree with the last part of your order of events. The combustion gas blow by, as evidenced by the discoloration on the piston, could not occur in the very short period of time (a few seconds, if that) that the crankshaft continued to turn over after the needle bearing failed, and the top of the piston hit the cylinder head (which should have also damaged the valves). This engine would have died almost instantly.

That degree of combustion gas blow by takes a significant amount of running time to build up. I'll say it again... this combustion gas blow by is the result of piston rings that were not well seated during the initial run-in of the engine when it was new.

I'm still curious as to how you are certain that the needle bearing cage was cracked from day one? (sorry, but I have to keep asking this question)
 
#29 ·
Sounds to me that Strelok understands exactly what happened, and it doesn't sound implausible at all. Let's hope that the issue here was one cracked bearing cage that eventually failed, rather than Honda having used a whole bunch of bad bearings...or that there is a design defect here that will result in this happening to a whole lot of engines at some point

Dan
 
#30 ·
From behind my computer hard to judge what happended , you gave a plausible description of the events leading to the failure but from your photos 30 and 39 this piston is not looking good. The photo 39 shows lots of undercrown deposits that are there for a while , they hinder cooling and that may lead to extra piston groove deposits causing the rings to no longer perform their sealing task and cause increase in blowby gasses.

I wonder if the Motul 7100 has been up to its task it's specs are OK for what I could find (API SL , JASO MA) but it's not exactly advertisement the way it made your piston look.

I am interested in the overal cost (ballpark OK) for this repair if UR willing to share.
Richard
 
#31 ·
i live in very hot climate, i live in Israel i was using the motorcycle in 44 Celsius (111 F) or more on twisty roads with lots of up hill riding so it's very good for my climate to have this little amount of deposits

the rings have enough room to move freely in the groove it was the first thing i checked, if the rings can move freely.
so it's not the case

i ordered the parts from partzilla
the parts i used(i putting absolute number without cents):
piston 34$
rings 11$
2 X new piston pin clips 0.5$
crank 163$
gasket kit 18$
oil filter 5$
4 X valve shims 19$
cylinder head stud and the nut 1$

251$ + 50$ shipping and handling
so pretty much 300$ is the total cost
 
#33 ·
... the rings have enough room to move freely in the groove it was the first thing i checked, if the rings can move freely.
so it's not the case...
I have just a couple more questions (I know, I'm starting to sound like Columbo)...

So when the piston hit the cylinder head, it didn't do any damage to the valves, or the cylinder head itself?

Do you have access to a Flex Hone (Flex Hones, Flexible Honing, Flex-Hone®), sized for the CBR cylinder bore?
The reason I ask this, is because a new cylinder for the CBR is inexpensive as well... from Partzilla about $45.00 USD. I've bought a few Flex Hones over the years and they can be pricey, especially for the DIY'er with a one time need (hopefully).
 
#34 ·
it took me 4 hours to disassemble the whole thing , clean and measure the major parts
i think the whole work will take me 8-10 hours

I have just a couple more questions (I know, I'm starting to sound like Columbo)...

So when the piston hit the cylinder head, it didn't do any damage to the valves, or the cylinder head itself?

Do you have access to a Flex Hone (Flex Hones, Flexible Honing, Flex-Hone®), sized for the CBR cylinder bore?
The reason I ask this, is because a new cylinder for the CBR is inexpensive as well... from Partzilla about $45.00 USD. I've bought a few Flex Hones over the years and they can be pricey, especially for the DIY'er with a one time need (hopefully).
not any damage to the cylinder head,and the valves didn't touch the piston only small deformation on the piston itself on the sides,
the piston is very cheap made, very thin walls and very soft aluminium
honda just did some hard coatings on the piston to piston pin contact surface
and molybdenum coating on the piston skirt
but the piston is cheap and very light weigh

nope i don't have access to flex-hone, i don't going to do any honing , i measured the cylinder with bore gauge and its almost ideally polished except for one small scratch on the piston skirt to cylinder contact zone which i going to polish a bit and just baby it for the first miles
 
#36 ·
First the dealrs in Israel very unprofessional. They can't rebuild engine that last for long term.
They don't even have micrometers and needed measure instruments.

Buying new cylinder involving ordering gasket kit a 35$ and payin for new shipping 50$ so its 120$ in total.
And if I will not gain full power raplacing rings and cylinder is very easy task, so I will replace them if needed later
 
#122 · (Edited)
First the dealrs in Israel very unprofessional. They can't rebuild engine that last for long term.
They don't even have micrometers and needed measure instruments.
Today I managed to get some info from Honda dealer mechanic in israel.
He says its a well known issue on this engine.
They already replaced dozens of cranks.

And the dealer told me, they don't do any honing.


Giko, not all engines getting honed before assembly
:confused:

My head is starting to hurt. Can someone pass around the big bottle of Motrin IB... 400mg should just about do it. :eek:

Perhaps that statement should read "not all engines in Israel getting honed before assembly"... Strelok you can't speak for Honda Motor Co. here... I know for a fact what their manufacturing standards and procedures are. You sir, are so full of it, the bullshit must be gushing from your ears.

Giko, if you believe that statement, I'd really like to show you that beautiful Florida swa... err... land. It includes water rights, lots of water. :D
 
#37 ·
So you don't need any new top end gaskets (Gasket Kit A) to finish your rebuild? They sell any of those gaskets individually as well... cylinder base gasket is less than a dollar.

What would the dealer there in Israel charge to order the new cylinder and base gasket for you?
 
#38 · (Edited)
I ordered kit b with cylinder base gasket

The dealer here charges 75$ for clutch cable - 3$ at part zilla

And 1170$ for crank

I don't even bother asking for gaskets.

To replace cylinder I need new head gasket and new base gasket and new cam chain hole gasket.
I will try with old one, if the ring would not settle properly I will replace cylinder and rings.
I don't have time to wait to another package

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