Can I use an R6 radiator cap on my WR?

4 replies to this topic
  • Bitteeinbit

Posted May 07, 2016 - 05:52 PM


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? 

  • Krannie McKranface

Posted May 07, 2016 - 06:13 PM


If it fits, it fits. 

If you were loosing coolant at the cap, there would be steam and visible fluid.............


Is you oil milky colored ?


Do your exahust fumes smell like sugar ?

Edited by KRANNIE, May 07, 2016 - 06:13 PM.

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  • Bitteeinbit

Posted May 07, 2016 - 07:22 PM


No visible steam, though I lose maybe 300-500ml per ride. It's been around 37-42c here lately, so definitely hot. I'll post a picture of my cap in a bit, but it definitely doesn't look like the rubber is good (and finally enough, looks totally different from other WR caps I checked out). Might be worth going for a ride with a different cap ($8) to see if it fixes the problem.

Exhaust might smell a tiny bit like sugar (but not really?). Hard to tell. Is that a sign that I'm too rich? Bike definitely gets hot. I sometimes ride in shorts or thin pants and the exhaust side is dang hot.

I did have a bad waterpump leak last month and changed the seals and bearing (and remachined the impeller shaft a bit). Last week I had a small seal leak so drained the oil. It didn't look very black (perhaps milky), but it was virtually brand new oil (one ride on it). Milky would be a sign that my seals weren't properly seated and coolant is mixing with the oil?

Edited by Bitteeinbit, May 07, 2016 - 07:32 PM.

  • Krannie McKranface

Posted May 08, 2016 - 05:08 AM


Milky oil means you have major head gasket leak or a pump seal leak (the most likely problem)



Sweet exhuast means you have a minor head gasket leak in the the combustion chamber


You cannot take metal from the impeller shaft to 'smooth it out'. It must be replaced.

Edited by KRANNIE, May 08, 2016 - 05:09 AM.

  • Bitteeinbit

Posted May 08, 2016 - 05:51 AM


Thanks, my head gasket is fairly new as the head gasket was busted when I got it, so hopefully that isn't the issue. I'll check the torque specs again just in case. I'll also double check the oil.

FYI, this is what my cap looks like (2005). Is it normal for the rubber to extend beyond the plunger piece? As you can see from the first two pictures (mine), the slightly work out rubber goes beyond the metal, whereas in other bikes I noticed it doesn't (pictured). It's flush with the metal. Is your cap the same as the first two pictures (extends beyond) or more like the third one (flush)?

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Edited by Bitteeinbit, May 08, 2016 - 05:53 AM.


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