I did something similar. I bought aluminum mesh off of Amazon. I cut, bent and painted it myself. I got a sheet large enough to make 2 for less than one prefabricated.I added aluminum sheet metal that I picked up from Home Depot by cutting it to shape and sticking it under the plastic radiator guard. Much cheaper than a canned aftermarket solution and I think it turned out great on my Scout ABS. No overheating or airflow issues. I rode without something for about 300 miles after buying the bike and noticed little dents in the radiator, so I would recommend picking something up.
Other members have reported success with using this aluminum alloy grill that you can get for cheap on Amazon. I might switch over to it eventually, just for aesthetics.
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