Frame and engine serial numbers, do I have an original motor?

Discussion in 'Honda CT70/Z50 Registry' started by Dakotaborn, Aug 12, 2018.

  1. Dakotaborn

    Dakotaborn New Member

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    I have a project CT 70 that I'm wondering about.

    The frame tag has the date of manufacturing as 9/71 with a vin of 2010992

    The engine is stamped CT70E-211143.

    My assumption is that this is an early K1 with a later motor.

    Can I get some help with this?

    Thanks.
     
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  3. OLD CT

    OLD CT Well-Known Member

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    Yes it is original and the engine is 151 #s apart. You have to take the 0 in the vin and add it in the second position of the engine #. Now it is 2011143, now minus them to get the split.

    2010992
    -minus -
    2011143 = 151 apart.
     
  4. red69

    red69 Well-Known Member

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    Correct me if I'm wrong, but in this case that makes the engine number higher than the VIN. Given that Honda trashed frames that weren't acceptable, that would make the engine number lower than the frame.
     
  5. OLD CT

    OLD CT Well-Known Member

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    I have seen higher and lower.
     
  6. racerx

    racerx Administrator
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    IDK if SNs were discarded, from the production sequence. They werr stamped into the frames so, more logical that would have been done to frames that passed Q/C...imho. Look at the uneveness of the characters.

    That said, looks like a mere 1-2 days worth of production...of both.
     
  7. red69

    red69 Well-Known Member

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    Looking at all that, what would you attribute the disparity of matching sequential numbers between frames and engines?
     
  8. red69

    red69 Well-Known Member

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    Could it be that the left frame half was stamped before the halves were joined and later possibly discarded as defective after final assembly?
     
  9. cjpayne

    cjpayne Well-Known Member

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    If there was a quality issue with the motor, they would grab the next motor and send the other back to be put in later. I guess they did this with the frames too.
     
  10. racerx

    racerx Administrator
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    We're kinda heading out toward left field, hereo_O.

    The explanation is a lot simpler & straightforward than Q/C issues, some of which don't make sense, in the context of a production line. What quality problems could be discovered with an engine, at that stage of the assembly process?

    In that era, engines would have been virtually hand assembled...on their own, dedicated, line. That's pretty much how carmakers did things then, as well. Frames, engines, etc were produced in batches...and at varying rates. With "numbers matching" classic cars, that typically meant having the right date code...within a few weeks, or months.

    IMO, far more likely that the frames were inspected, then VIN stamped before paint. Once there was an adequate batch lot of engines, frames, etc they were joined on the assembly line. Gotta give the OEM credit for keeping the SNs as close as they did. Never heard of a "SN assignment manager" job title...
     
  11. red69

    red69 Well-Known Member

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    In addition to OLD CT, has anyone else seen higher number engines mated to frames? Bob, you've probably seen more of these CT's than anyone. Have you ever come across this?
     
  12. kirrbby

    kirrbby Well-Known Member

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  13. allenp42

    allenp42 Well-Known Member

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    I have seen it several times on bikes that smell like an original unmolested. Agree, not very scientific but I have seen it. My HK0 has an engine a few hundred above the frame vin. I tend to agree with Bob on this one. Seriously doubt there was spec during manufacturing to keep the VINS within "X amount". The normal rule I thumb I go by is +/- 400ish.
     
  14. allenp42

    allenp42 Well-Known Member

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    Just checked my 77. It too has an engine 184 higher than the frame.
     
  15. OLD CT

    OLD CT Well-Known Member

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    Which one? 2 Bob's involved here, LOL! My HK0 vin is higher than the engine.
     
    #14 OLD CT, Aug 13, 2018
    Last edited: Aug 13, 2018
  16. red69

    red69 Well-Known Member

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    Not me, the other one with with all the knowledge.
     
  17. allenp42

    allenp42 Well-Known Member

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    True. I was referencing the comment about the "S/N Manager". I doubt Honda was thinking about the vintage market that would spring up 50 years down the road when they were assembling CT70's back in the early 70's. One "theory" I've heard is that Honda would pull engines now and then and send out as replacements. No idea if this theory is correct or not. Just know what I've seen and really don't know definitively if real world examples are factual or been altered in the last 40+ years.
     
  18. Gary

    Gary Well-Known Member

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    Good theory but.... Replacement engines I think or cases,I know for sure don't have serial numbers,so I think replacements did not come from the bike assembly floor. I'm guessing frames and engines were stamped somewhere after being assembled but before being delivered to the production line. If they were stamped on or near the line why didn't they just stamp the frame number on them as they came down?Unfortunately due to our different cultures we will never know. Frame serial numbers never seem to have paint in them as if they were stamped after painting,I know replacement frames have no serial numbers stamped. Does anyone know for sure if a replacement engine has serial numbers ? I know Triumphs serial numbers matched and were stamped at the same time while on the line being assembled.
     
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  19. cjpayne

    cjpayne Well-Known Member

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    My HK1 is too. 183 higher.
     
  20. allenp42

    allenp42 Well-Known Member

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    I have only seen one and I think it was a 78. It did have a serial number, and was on e-Bay for about a year before it sold. In reading through some postings here on LH, others have seen a few replacement engines with serial numbers. I don't have the slightest clue as to how many.

    Somewhere, I have a file with notes of HK0's I have seen where I noted the frame, engine numbers and a few minor differences. I don't have anything on K0's, and haven't looked closely at vins beyond the bikes that I own.
     
  21. racerx

    racerx Administrator
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    X2...
    The last little bit of :poop: in this game...time. SN & model numbering requires have changed over the years. A model year declaration was required as of 1975. That further blurs an already murky situation...the question being how many motors were service replacements and how many were pulled from bikes, or never went in. I've seen late-model (i.e. 12v-era, CDI) motors that wore serial numbers, mostly CRFs and they've typically retailed for $1698. Bear in mind that the "sample" number is very small, too small imo to bet the farm. Even more confusing, some of the early ST70 Dax model engines also lacked SNs and these were installed in production bikes. Best info I have is that, for the most part, Honda never sold complete engines but..."never" can be a dangerous word. It's not much of a stretch to believe that a few brand new bikes were damaged before they could reach a showroom, which would explain why there are a few widely-scattered NOS engines, with factory SNs.
     

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