Webmaster Note: Contrary to this article, the recommended sparkplug for the R100GS is a W7D*

Herewith the first salvo in the Great Sparkplug Roundup:

Source: Chitech Tuneup Manual

All plugs 3/4" reach and extended electrode

Old Bosch #  New Bosch # Copper Core #  Heat Range   Model/Yr

W175T30	        W7D         W7DC         Hottest     All R80
W200T30         W6D         W6DC                     All /5/6
                                                      R90S
                                                     Some /7
W225T30         W5D     
W230T30         W5D1        W5DC         Coldest     All R100

Notes: The model/yr plug recommendations are subject to variation depending on how you ride the motorcycle and the outside temperature. The rule of thumb is:

If you ride hard, fast, and in hot weather (conditions where the engine runs hot): Use a cold sparkplug (such as a W5DC).
If you ride easy (moderate to slow) and in cooler weather (conditions where the engine runs cold): Use a hot sparkplug (such as a W7DC).
If you are an average rider use the heat range indicated in your owner's manual or the above chart.

Source: Chitech Tuneup Manual
All plugs 3/4" reach and extended electrode

 Old Bosch #  New Bosch # Copper Core #  Heat Range   Model/Yr
 W175T3         W7D         W7DC           Hottest     All R80
 W200T30        W6D         W6DC                       All /5/6
                       				       R90S
						       Some /7
 W225T30        W5D     
 W230T3         W5D1        W5DC           Coldest    All R100

Notes: The model/yr plug recommendations are subject to variation depending on how you ride the motorcycle and the outside temperature. The rule of thumb is:

If you ride hard, fast, and in hot weather (conditions where the engine runs hot): Use a cold sparkplug (such as a W5DC).
If you ride easy (moderate to slow) and in cooler weather (conditions where the engine runs cold): Use a hot sparkplug (such as a W7DC).
If you are an average rider use the heat range indicated in your owner's manual or the above chart.

Source: NGK sparkplug conversion chart published in Chilton's Motorcycle Troubleshooting Guide.
14 mm 3/4"

Old Bosch #             NGK         Champion      Heat Range
                (projected type) (Y=projected type)

W175T2   W175T30        BP6ES      N12Y, UN12Y,     Hotter
		                   N11Y, N10Y
W225T2   W230T30        BP7ES      N9Y, N8Y
W260T28  W265P21        BP8ES      N6Y, N7Y         Colder

Note: This chart is furnished as a guide. Due to differences in design and materials, plugs produced by various manufacturers do not have exactly the same heat range.

Source: Clymer BMW.

Bosch #             	Champion            Model

W175T30 (W7D)		 N9Y         	    R80/7
W225T30 (W5D)		 N7Y                R50/5,
					    R60/5,/6,/7
W200T30 (W6D)		 N7Y		    R100/7, R90/6, S,
					    R75/5,/6,/7
W225T30 (W5D)		 N6Y		    R100S, RS, R100T, RT

Source: Haynes BMW.

Bosch # 				Model

W200T30 (W6D)	                      All R75, R90/6, S,
				      R100/7 up to 1978,
				      All US 1000 models
			         	1981 on
W225T30 (W5D)		              R60/7, R65, LS,
				      All 1000 (except R100/7 1977-'78)
                                      up to 1980
W230T30 (W5D1)			      R50/5, R60/5,/6