Vintage Dirt Bike Q & A

Honda used the billet crank in some of the 73 cr250's it had the two holes one on each side of the rod and less cut away. What I wanted to know is did they use them for the mt250 in 73? I have two cranks one is the normal crank with a ton of cutaway but the other in pretty round with two holes one on each side of the rod. Is there any benefit to a billet crank?

In terms of strength and durability, billet is superior to cast. Replacing a cast iron crankshaft with a forged billet
crank is ususally one of the first orders of business when building a high performance engine. Most if not all of
Honda's works bikes have billet cranks.

In the case of Honda, The '73 CR250M was the company's first high performance two stroke, having been involved
only in road racing (four stroke) up to that point. I don't know if the billet cranks were used because of concerns
over reliability or due to expediency to get the new bikes to market. It takes less time to forge a billet piece
initially then it does to tool up to produce castings. Once the tooling is done, it takes less time and is far less
expensive to produce cast parts in mass.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

I've got a extra crank (not billet) that has a copperish color to castings?? You guys got any info on it?

From what I understand, Honda put the billet crank in the first thousand or so engines they built for the 73 cr250m. I have a few myself and they do have numbers scribed into them. They are hard to read. I'll try to post pics of them soon.