Thruxton Low Clip Ons Thruxton S Brake Level

Hi

The angle of the low clip ons means that the brake fluid is at best half way up the sight glass and sometimes considerably less depending on where I turn the handlebars. However, I can't find a level position to top it up. No matter what position I have the bike on the stand or where I turn the bars the fluid is up the top of the reservoir in one corner and dry at the opposite one.

Just seems odd, and I worry it could get air in the lines.