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I cracked the upper crankcase on my CB200 and will need to replace it. My concern is that the engine number is stamped onto this and changing it will result in a different engine number. Is this going to be a major problem or does it not really matter?
Im in NSW Australia by the way.
Great thanks DrJ! The only other thing is will there be an issue with the different number? For example is it matched to the frame number, or will it be a problem trying to register it? or is it just a number to distinguish engine and had no need other that that?
Some would argue mechanically it actually does matter. Engine cases are machined as a matching set - just like cylinder heads and rocker covers where there is no gasket (which is why they have matching numbers stamped on them).
Your two engine cases were machined to be a perfect fit with each other. Yes, good chance a different 1/2 will work, but you're dealing with a complex set of machined faces over a fairly long span that need to fit perfectly in order to seal properly with a thin layer of Threebond spread on them.
You'd be best off getting a complete set of cases.
Oh, and as to the number on the engine, here in Canada, and I'd think in most places, the engine number has nothing to do with the bike registration. Best thing to do is call up your Ministry or whatever the authority is there and tell them you need to replace the engine in your bike and see if they care. You don't need to say who you are.
Some would argue mechanically it actually does matter. Engine cases are machined as a matching set - just like cylinder heads and rocker covers where there is no gasket (which is why they have matching numbers stamped on them)
It matters if the cases are vertically split like on British motors but not so much on horizontally split cases. Matched cases means the main crank bearing bores are drilled through at the same time while both sides are together. On the horizontally split Honda, the crank is fixed to the upper crankcase half, you can remove the bottom case half without disturbing the top so everything above the crankcase center is still aligned. Also, the bottom half of the Honda case can be purchased separately, it has it's own part number. If the crankcase is matched, you wouldn't be able to buy just the bottom half. And lastly, I've done this with a CB350 motor. I broke the kickstart spring tab on a bottom case half and replaced with another. Buttoned it all up and the motor ran fine. Honda castings are very precise and consistent, everything lines up.
I don't want to be a downer Joey, but I think you will find that the engine number does matter in NSW!
My various rego papers all carry the engine number as well as frame number. When you go for your pink (or blue) slip the discrepancy will probably cause a problem. You will at least need good paperwork covering the purchase of the new case.
If the number on your crankcase changes, it will only matter if you have current registration papers for the bike because the new engine number will not match the rego papers. However if you are re-registering the bike and getting new rego papers, then you need to get a "blue slip" where they make note of the frame number and engine number. From then on those numbers are a matching pair and are noted on the registration papers.
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