Carburetor o-ring sizes

[Egaeus]

I don't know if anyone has done this, but I estimated the size of the carburetor o-rings while I had it apart since they're so dang expensive from the dealer.  If someone knows the official sizes, please correct me.  It's hard to measure ID etc, on something that flexes.

O-Ring                                                                 Inside Diameter     Cross Section
Vacuum take-off (the small ones on the top)      ~4mm                    ~1mm
Idle mix screw                                                      ~2.5mm                 ~1mm
Float valve seat                                                   ~7mm                    ~2mm
Choke (on the floats)                                          ~5mm                    ~1mm
True Piston Guide (not available from dealer)     ~10mm                   Square Cut - ~12mm OD and 1mm thickness
Improvised Piston Guide                                      10mm                     1mm

[sledge]

O rings are a science on their own and you must always use the correct size item for the application and replace them like for like. This link will give you info that will help you to identify common sizes and materials, ISO reference numbers for ordering and correct groove sizes. You are better sourcing them from a hydraulic engineering company than paying inflated dealer prices.

http://www.prepol.com/index.htm

[GeeP]

Yes, when measuring an O-ring, it can be very difficult to measure the ID and OD due to flex.  To overcome this problem, find a drift pin that the O-ring will slide onto.  Slide it down until the drift brings the O-ring into round but does not stretch it.  Measure the OD with a caliper.  Now remove the O-ring and measure the cord diameter.  Subtract 2X the cord diameter to arrive at the ID. 

If the O-ring is severely deformed in one axis only you can determine the cord diameter by measuring the cord at the thickest point and the thinnest point.  Average the two measurements to arrive at an approximation of the cord diameter.

[coll0412]

If you are looking for common sizes check out www.mcmaster.com

and type O-ring into the search

1mm Cross sectional thickness is a standard size, as well as the diameters you list