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Anybody know the size of the O Rings for the Throttle Body Big Brass Screws and for the Oil Fill Plug for a 2002 1150RT? My nearest dealer is 120 miles away, and through Chicago, so I thought I would try getting these locally.


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I don't have the sizes but, O-rings are typically sized by ID and cross section so, for the BBS, measure the diameter of the inside part of the groove and then the width of the groove. Using a cross reference chart to either metric or dash sizes, find the closest match. Ditto for the oil fill.


Another alternative is mail order from A&S or Chicago BMW.

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The oil filler cap “O” ring is 18mm X 4mm. The air screw “BBS” screw “O” ring isn’t listed so on that you will probably need to visit your local auto parts store with an original in hand to match it up. If you buy from a local hardware store just make sure it is oil and gasoline resistant and not made for plumbing applications only.




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Danny caddyshack Noonan


If you have a caliper or mic, look online for metric o-ring gland size chart. Using the dimensions for a static o-ring, you should see the standard size somewhere on the chart. Many of them convert straight over to a non-metric o-ring. Especially in this application since the pressure across it is very low compared to design standards of 1500psi.

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