Mikuni BSR36 float valve seat & needle jet o rings

The Mikuni BSR36 found on the S and SM commonly have the float valve seat o ring leaking.... its not normally the needle or seat damaged or worn.

The O ring is an odd ball size 7.75 I.D. x 1.53mm only seen available from the OEM in a valve set for this model. VALVE ASSY,NEED 
13370-29FA0

More commonly found is a 1/16 by 5/16

Chemical-Resistant Viton® Fluoroelastomer O-Rings 

It is a little tight but with some O ring lube it will work...

the Dash Number is 2-011

 

Or 

Chemical-Resistant O-Ring Viton® Fluoroelastomer, 1.5mm Wide, 8mm ID

If using Viton try the durometer 75A (Medium) or durometer 60A (soft)

 

If you can find the right size in Viton material, all the better. it will resist ethanol in the gas for longer periods of time then the rubber o ring commonly used. Keep a few on hand and if removed for cleaning replace each time,  as they get very difficult to use a second after aged a bit without damage to the O ring or carb body.

Thanks to @S.O.A.N.Z for finding the O ring dimensions for the needle jet O ring part #13246-43010
D1 = 5.3mm
D2 = 1.85mm
This O ring is available as an individual component, unlike the float needle seat, but if your looking for a non OEM source, you now have the size. 

 

Jet needle O ring in RED
Float needle seat O ring in GREEN

5a78703fd038e_seatandNeedleJetOring.jpg.0bb101e2fb661c36e8909be6c91aa0c0.jpg

Edited by Erik Marquez
New information

Another Edit: Thanks to a forum member another source for the proper size viton O ring was found on Amazon 
Amazon sellers and links are perishable so I wont include a link.... but a search of "1.5x7.5 Viton O-Ring, 75A Durometer, Round, Black, Viton, 7.5 mm ID, 10.5 mm OD, 1.5 mm Width (Pack of 10)"  or some part of that string gets you a hit on Amazon now, and should in the future if a seller has these listed. 

I paid $3.00 for a pack of ten at the time I ordered 26 Jan 2018