My WR has been boiling over lately, and I noticed the coolant wasn't returning back to the radiators. It would take a LONG time before it would finally get sucked back in (20mins), vs the usual 5 minutes from when I first got the bike (2005 bike bought a few months ago). Also, I have to top off coolant after each ride, but no obvious leaks in the system.
After checking my radiator cap and comparing it to other WRs and a few Honda's, I noticed it's likely busted and that's how I'm loosing water/coolant. The rubber ring underneath isn't flush with the metal plunger piece (way bigger) and the rubber has a tiny hole and worn/torn a bit. No original caps around so I went looking for second-hand ones. Found a crappy Chinese one (tin metal and 0.9 rating), but later on managed to find found original ones from an R6 (or R1, forgot now).
Are all Japanese bike manufacturer radiator caps the same (size-wise)? A bit of research reveals the R6's radiator cap is also 1.1, and I'm assuming the cap and radiator openings are the same size.... Am I wrong in assuming this?