BTC1984: Before you order this belt, if you haven't already, you might want to see if you can find the numbers on your existing belt that indicate the length of the belt. This could vary from the length of the belt on the stock B4200 tractor. While the M18 engine is a Kubota Z600, which appears to be what was used on the B4200 tractor, the alternator setup on your engine may be different than was on that tractor. And in any case, in the ensuing 30 plus years since the Z600 was made your setup might have had modifications. For instance, the Z600 in my boat uses a 990 mm (39") length belt vs what I think is the 789 mm belt you posted. The one you posted may be correct for your setup but you might want to check that. If there are no numbers on your belt you can get at least a rough idea of the length by wrapping a string around the existing belt and then measuring that.
Sorry if what I said about the M18 being a Z600 might have misled you about the belt length. For actual engine parts such oil and fuel filters, injection pumps, gaskets, coolant pump, injectors, cylinder heads, glow plugs etc. you can use Kubota specs. For things that are extraneous to the engine, like the alternator, or not on the stock tractor engine, like a raw water pump, you have to look away from Kubota.
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