Bridgestone Motorcycle Parts Discussion Board
General Category => General Discussion => Topic started by: moonpup on July 02, 2015, 12:21:42 PM
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While recently cleaning up some parts, I recognized some numbers that I hadn't thought about since I got out of the 240Z car club. Thought I'd post a little something about these in case anyone here was curious about them.
I "borrowed" this from the old car site I was a member on and changed the numbers to reflect the ones that are in the pic in an effort to give y'all a quick easy explanation...
"These numbers are dates in the Showa format. Without getting into too much history, 'Showa' refers to the Emperor of Japan and at the time of your motorcycle's/part's assembly, the Showa period was in existence. The Showa period begins in 1925 (the Emperor's date of birth) and the '42' in the pic added to it (kinda smudged), is the year (1925 + 42 = 1967) and the '8' would be 8th month or August and the '10' would be the 10th day."
So the right side crankcase cover that this number is on, was made (or inspected) on Aug. 10th. 1967.
Voila ;D
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WOW DM, learned something new again, your just an overflowing wealth of useful information...DL 8)
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Next time you need to break the ice with a stranger, ask them if they know anything about the Showa date format.
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Next time you need to break the ice with a stranger, ask them if they know anything about the Showa date format.
haha... does it work with women? :o
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that's very interesting you learn something new every day
listed under is everything I know about women .
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hope that helps
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Probably works better than "you come here often".
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I learned to read , by trying to read Floyd Clymers Cycle Magazine. So this just continues my education. thanks
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Thanks for that Moonpup, I enjoy information as such. I'll try to remember to include it in my next article for Tansha magazine, should impress a few.
Z
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Hi Mike,
Great bit of information. Another piece fitted in the the BS history jigsaw.
I have often noticed these numbers and thought they could be a production batch code or a date but couldn't reconcile the year. This would explain it.
Just had a look at two right side covers in the workshop, 42 6 8 and 43 3 9 which do give matching production year dates for GTRs with VIN code dates of July 67 and June 68.
Not too sure about the last two digits, I agree, they do look like month/day numbers but I don't remember ever seeing a number higher than your '10'. Any of you guys got a part with a number above 10 ?? Did imperial Japan use a different dating system.
Great post DM, Brian.
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Not too sure about the last two digits, I agree, they do look like month/day numbers but I don't remember ever seeing a number higher than your '10'. Any of you guys got a part with a number above 10 ?
Hi Brian,
This "dating system" has been discussed quite a bit over on the Z site and by some very knowledgeable "experts" that are well versed in the Japanese way of doing things. I'm confident that the 8 & 10 in my example refer to the month and day respectively.
The Z cars have a ton of parts with these stamped markings in one form or another, with many examples pictured having numbers above 10. Unfortunately, there doesn't seem to be as many opportunities to find these stamps on our bikes. I've only seen 2 or 3 examples myself.
I'll keep my eyes out for more though and in the meantime, maybe some other members will chime in with their finds.
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Here's another right side crankcase cover I had access to. This one is 42.8.12 or August 12th. 1967.
As far as how high the "day" will go, who knows, maybe production for this particular part was limited to the first 2 weeks of the month and then they moved on to another piece? I'm not very well versed on how manufacturing companies do things.
On a side note, 8/12/67 was a Saturday.... ;D
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Hi Mike,
Well, that gets us up to 12 but either number could still be a month or a day. I'm not questioning your knowledge on this one, just curious.
Do any other parts have similar numbers on them. I've just done a quick check on the alloy parts that I can get to easily and can't find one. The set of crankcases I'm working on have been vapour blasted so won't show a number.
Keep up the good work, Brian.
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one of mine says 42 9 26 the other has nothing
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God Bless you Coxy! ;D :D ;D
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The stamping on mine is too faint to read from a July '67 build GTR. ???
...bert
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Do the Hondas,yamahas, etc have these date stamps on there parts?
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Do the Hondas,yamahas, etc have these date stamps on there parts?
Hey Paul, My guess would be yes considering they're all over the Z cars and can also be found on some of the Bridgestone parts. Probably a government requirement of some sort.
Here are a couple stamps I got off the car site to show some different styles. The ones I posted from my Bridgestone show a faint circle off to the bottom of the numbers but they don't sit on top like these nor do they have a Japanese characters as well...
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Hi Mike,
'Me of little faith' :D ;D :D. Coxy's number settles it - Year, Month, Day as you said Mike.
My money would be on it being an inspection mark at some stage in the engine manufacturing process. A final check the engine was timed correctly, gears and kick start worked and everything was in place before the right side cover went on ?? The left crankcase side covers don't have any stamps, suggesting these are not production dating marks.
Brian.
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Good guess Brian. Mine was a date of manufacture mark. It would be interesting to see if these are all unique to the specific Bridgestone part or if we find duplicates. Duplicates could indicate a lot code or that multiple engines were completed per day or ???
...bert
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I have 3 right case covers available (didn't picture one) and they are....
42.8.10 / 42.8.11 / 42.8.12
3 engines, 3 consecutive days.
I'm sure I saw them on something else, just can't remember what and can't find it or any others at the moment.
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Ok guys, after an exhaustive search in the Great Library of eBay I discovered another one of the elusive number stamps. This one dated 40.11.25 and was located in an nos wheel hub.
This prompted me to take on a potentially dangerous journey to the desolated hot & humid garage cave located in the north east corner of my ancestral lands, where in the hub of an ancient relic, I found the numbers 42.8.14! Unfortunately, I was unable to take any pictures as the extreme heat, humongous cockroaches and leaping lizards forced me to flee. :o
I must rest now before any other expeditions are attempted! ;D
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ok so why would one of mine have nothing ? maybe it did not get inspected
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I inspected 4 of my stones today, same find as coxy, but in my case no stamp on any of them?
DL
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I bought the 200 motor that Richard listed for someone in the classifieds. Turned out to be a 175, but that worked out better for me and more on that later.
Here are the insides of the cases of that motor that was on a October 1966 built 175DT.
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...snip... My money would be on it being an inspection mark at some stage in the engine manufacturing process. A final check the engine was timed correctly, gears and kick start worked and everything was in place before the right side cover went on ?? The left crankcase side covers don't have any stamps, suggesting these are not production dating marks.
Brian.
Wouldn't the inspection stamp on the nos wheel hub I found on eBay indicate it was placed there as an approval of the part itself vs. the assembly process?
As far as no stamps being found on the left covers or some of the other members right covers, wish I had an answer for that, but I'm clueless for the moment. ???
On the Z cars, they're on a lot of electrical parts, on the backside of the dash, on top of the gas tank, gauge housings....ect. However on our bikes, at least for now, they seem to be relegated to aluminum parts only. Hummmm?
EDIT: Been doing some more thinking Brian ( probably taxing the grey matter a bit much ;D ), and since the wheel hub I found on eBay is not a separate piece by itself but part of a complete wheel (hub/spokes/rim), the stamp could very well have been put there to approve the assembly of the total piece and not just the hub. Oh well, back to the drawing board....
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Here's something else to think about. These are the dates from 3 different pieces off the same engine.
The first is on the upper main crankcase (42.9.12), followed by the one on the lower main crankcase (?.8.28) and lastly, the number on the right crankcase cover (42.8.11).
They're all over the place (date wise). Did it really take over a month to put these engines together or does this suggest individual part dating? You'd think that if it was an assembly inspection, then the right cover would have the highest date.... right?
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Makes me think this isn't an assembly related stamping but either a manufacture date, manufacture batch date or manufacture inspection date. I'm not sure what the quality control measures were 50 years ago in an assembly area where these bikes were built.
It's great chewing gum for the mind Mike - keep it up.
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Looks like (as dcr says) lot code, inspection code, or date of manufacture code for the specific part to me.
...bert
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do you think it would be :o to find a person that worked at the plant back in the day and interviue them?????? i worked at a tool and die plant back in the 70s..... my job was to take 55 gal. barrles off the line... see how much they weighted... looked up the parts # taged it... then stored it.... parts go togeather by the ##s we allso made the shells for the handgernades for nam...... i never saw were they went.... ::)
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Nice DM, have to agree with dcr and "The Bertski", parts mass produced, dated, then shelved until needed for final assembly...DL
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do you think it would be :o to find a person that worked at the plant back in the day and interviue them?????? ...snip....
I would love for that to happen and it could potentially provide some answers to a lot of interesting questions. However, that would need to happen soon, as those folks aren't getting any younger!
The Z car community was fortunate to have access to several key individuals involved in both the design & manufacturing end of things. If only we had the same access.....
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Where would you even start to find a former Bridgestone motorcycle assembly plant worker? Craigslist?
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Kotaro-san might have an idea.
...bert
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Hi All,
Mike, dcr, Bertski and DL, you've cracked it.
All the stamped alloy parts have extensive machining operations and other ancillary parts which had be fitted before they go on to an engine, such as the oil baffle plate in the upper crankcase and the oil pump drive bush/oil collector trough for rev counter drive in the right case side.
You would think the left front case side should be stamped as it has the clutch operating screw fitted. Maybe its just worn or washed off over the years.
Brian
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Right On Brian, sounds like a perfect time to crack a cold one...Cheers
DL
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Another case cracked by the BS archeology team. Nice!
...bert(ski)
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Here is another "what does this mean" item I noticed but never really thought about. The left and right crank bearings on my 175DT have "C3" manually engraved in them. I know what the C3 means, but I wonder why they inscribe it on the actual bearing. These are the only 2 that have it - none of the transmission bearing have this marking. I have disassembled four 175 motors and they are all the same in this regard.
For those wondering, bearings have a rating of C1 thru C5 which indicates the internal clearance. Bearing internal clearance is defined as the total distance through which one bearing ring can be moved relative to the other in the radial direction (radial internal clearance) or in the axial direction (axial internal clearance).
Suffix Radial internal clearance
C1 Less than C2
C2 Less than Normal
CN Normal, only used in combination with letters indicating reduced or displaced clearance range
C3 Greater than Normal
C4 Greater than C3
C5 Greater than C4
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Not sure I can explain the upper pic, but the 6304 designation is standard bearing interchange nomenclature. If you look at many BS bearing part numbers you will find a 4 digit 6xxx in the number. This indicates BS bought off the shelf bearings for that particular application. In the above case a 6304.
...bert
Some more info on bearing nomenclature.
Bearing Nomenclature
You can learn a lot about a bearing just from its part number.
A typical bearing is the 6203ZZ bearing. This part number can be divided into it's components:
Type Code - 6
Series - 2
Bore - 03
Suffix - ZZ
For more google bearing nomenclature.
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Suffix Radial internal clearance
C1 Less than C2
C2 Less than Normal
CN Normal, only used in combination with letters indicating reduced or displaced clearance range
C3 Greater than Normal
C4 Greater than C3
C5 Greater than C4
C3 clearances are normal for electric motors due to the armature shaft and inner race normally running hotter than the surrounding housing and outer race, so the internal clearance is greater than normal at room temperature, but normal under operating conditions. I'm not certain if this is the reason for the crankshaft bearings being C3 clearance or if it is an alignment or axial thermal growth or ??? We do know the crankshaft flexes enough to fatigue and break the center pin, so it may be an alignment issue. Another subject for speculation.
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Hey gang, I found these letters stamped behind the knee pad on the right side of a 350 gas tank . I don't recall ever having seen anything like them before and haven't a clue what their purpose/meaning is. ???
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Hey You..... Maybe a suppliers identification...technicians identification...quality controls stamp?
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Here is a tank from my 175DT.
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Rods from 3 different 175 motors. Any guesses on the meaning of the single digit letter/number?
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Here is a tank from my 175DT.
Nice, different model, same first letter and different second. Also looks to be on the right side of the tank as well.
Gotta mean something..... ???
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Dan
I also noted different numbers on 90 con rods. It would be interesting to know what they indicate.
RayK
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What, no BS inside the keystone?
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Are their weights slightly different ?