I have to replace the speedo on my 242DL. Found one on ebay with 20,000 more miles than what I have. My question is can I roll back the odometer without screwing it up or taking it completely apart? Or should I leave it alone and document the mileage on both speedos?

If your present speedo isn't working it may be because the gear wheel has cracked and lost its grip on the shaft (as B.C. mentions). Open it up and take a look. A drop or two of Loctite may solve the problem.
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.

The main point is to get one with the same r._ _ _ _ number and max speed number as your present speedo. Otherwise it may fit but tell huge lies.

I can guess that 20,000 miles is 10% or less than your present mileage. Is it? If so, forget it. You can keep track in your records book, take it into account on the t-belt change or other maintenance, then move on.

I understand that the mechanical speedos (as opposed tothe electric ones) fail due to a gear loosing its grip on a turning shaft. That's what happened to my 984 speedo. Thus messing with the gears might precipitate such a failure.

Of course, there might be another BB'er with a better answer.

Good Luck,

Bob

;>)