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If the pilots’ are yellow, then they need to be cleaned. Unless your on a different gas than it was previously set up for. What do the main burners look like when lit? It’s not uncommon for foreign particles in the gas lines to be disturbed during a move. Once loose they may burn yellow or partially clog a orifice causing a improper mixture.  The vendor of a used piece of equipment does not want to add a service call to it as he loses money. We don’t know what king of agreement you have with them. But no, it should be a clean blue flame.
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If it continues to burn yellow, you’ll wind up with a heavy carbon deposit above and around it. Sometimes effecting the main burner lighting.