Vintage Dirt Bike Q & A

Got a few questions that nobody seems to be able to answer with any certainty about the frame and engine numbers for the 73-4 CR250's. How many 73 CR250's were made? What frame # did the 73 CR250's start with? What frame # did they end with? What engine # did they start and end with? Did all the 73 models have hand stamped engine numbers? Did all the 73's come with the billet crankshaft? How far apart can the engine and frame #'s be and still be considered to be correct? You would think that as long as I've been messing with these bikes that I would know the answer to these questions, but so far nobody has had an answer.....only lots of uncertain guesses. I just picked up a 73 CR250 with a frame number in the 1700's and engine numbers in the 1300's. I'm 99% certain that this is a matched frame and engine set, but was looking for examples of other engine and frame combinations to get some idea of how the numbering system worked. If any of you reading this would take the time to make a note of your frame and engine numbers to share with others on this board, maybe we could make some sence of this. If you do take the time to make a note of the numbers, please don't give out the entire number or some crook may get ideas...... Here's an example to start with. Frame number 77X and engine number 49X. Would this be a matched set?

Good questions. All I could find out was that the frame # started with CR250M-1000216

I can only answer about how close frame and engine #'s can be. A good friend and I had 2 CR250's that we bought used in 1975. Mine is long gone and I don't have #'s,but he still has his bought from original owner who never raced it. Frame # 1023xxx engine # 1026xxx they are 388 different. Not to confuse issues but just to give you an idea about Honda serial #'s, here are some I have. 1969 Honda 50 minitrail purchased new in 69 , 5559 between frame and engine,1969 2nd owner 70 minitrail with #'s on original title, 283 between, a 1974 TL 125, 306 apart and 3rd owner 1976 MR 250, 1 apart. You could get ahold of American Honda maybe they would give you the #'s but that would only be for the USA, which opens a whole set of new questions.Did the Australian bikes differ from US ones? Was the numbering the same, they must have come from the same factory, what about New Zealand or Europe? It will be interesting what answers will come up.

It seems that the frame numbers are around 300 to 400 numbers apart. That seems to be a pattern? Your 69 Z50 seems to undermine that idea though. I wonder if they start out close and get farther apart as engines on the line were rejected during inspection?

My thinking is the more produced the further apart they can be. Could that be because more than 1 assembly line is going for more popular bikes? Don't forget some complete engines enter the parts inventory also, but I'm not sure they have serial numbers. Replacement frames have no numbers.

I'd bet that quite a bit of the engine production went into destructive testing and works bikes. To me lower engine number then frame is suspect.

There is the simple replacement of blown engines and spares for race teams. I doubt if they make separate runs for this rather then just stear some of the engines produced into the replacement pipeline. It's quite possible they made twice as many engines as finished bikes for example.

The engine number will always be higher than the frame number, they pulled engines off the assembly line to sell as replacement engines. There were somewhere around 2000 billet cranks, most of which are long gone. They made close to 30,000 73 & 74 Elsinore 250's. There are many differences between the first 73's and the last 74's, both engine and frame. If the engine and frame numbers are within a few hundred numbers of each other it is a good chance they came together from the factory.

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Sam Alexander

1974 Honda CR250M
1976 Honda CR250
1974 Maico MC440
1974 Maico MC250
1977 Maico AW400

Sounds to me that there really isn't anyway to determine if a motor is actually the original matching motor unless they are so far apart that one is a 73 and the other is a 74. Honda must not have thought it important to match motors to frames.

My best guess is that the engines that were frame-specific (i.e. CR250m engine ONLY used in CR250M frame), the closer the numbers would be to each other. In the case of the horizontal 50 and 70 engines, they were used in a lot of different applications, so the odds of being anywhere close to the frame number might be remote.
But as someone guessed, I don't think Honda cared one bit about having frame numbers and engine numbers match. Tooling goes bad during production and some engines and frames are likely scrapped along the way. You could buy replacement engines and frames and they probably were made on the same assembly line as the ones that made complete bike. etc. etc.

hi
i have a early cr250m bought from original owner in spicewood tx.
frame no is 90X
engine no is 110X
billet crank
have another engine 13xx billet crank
jim garvey
sydney australia

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Jim Garvey
1x honda cr250m 1973 in bits
1x honda cr250 champion dirttracker
1x yamaha tt500 dirttracker 1976
1x yetman triumph dirttracker
1x tt500 longtack speedway bike
1 x 1940 350 ariel speedway bike
1 x bultaco astro grasstrack bike antig

CT 70 H motors and frames are real close. Lower production compaired to other models must be a factor some how. 3 of my bikes the frame is a higher serial number than the engine.My MR, probably the lowest in the number of bikes produced compaired to CR's, Z's,CT's and TL's has the engine higher than the frame by one. I'd bet Honda stamped the motors and frames as the individual components were made and as they were delivered to the assembly line and assembled together they could get miss matched.When your building 150,000 Z's a year your not going to slow down or stop the line to keep matching numbers. Other brands with matching numbers must have been stamped after assembly, otherwise how would you keep them together?

I had one with hand stamped numbers not thr cr250m part just the numbers and when I looked into it ,I found out that only the very early 73 models had hand stamped numbers

The very early cases were different, and you could also have a set of replacement cases, those came blank and the dealership stamped your case numbers on the new cases. Lots of the early cases were exploded due to the poorly designed transmission gears. They did make major improvements in a hurry over the first few hundred engines produced. The cases also recieved reinforcements to strengthen them along the way too.

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Sam Alexander

1974 Honda CR250M
1976 Honda CR250
1974 Maico MC440
1974 Maico MC250
1977 Maico AW400