GSXR400 radiator cap rating

[hutchwilco]

Hi guys,
My GK71B has some Nissan cap on the radiator put on by some previous owner obviously.
The rating label on the top has peeled off and I can only make out a possible "0.9"

A quick search tells me a common rating for Nissan caps is 0.9 bar which is 90kPa.

My GSXR manual specifies 110kPa +/- 15kPa = 1.10Bar.

Previously I've had issues with the bike heating up on long rides (more than 45 minutes). I've had the coolant dripping out on hill rides. Luckily my daily commute is 20 minutes. I'm tempted to blame this on the cap, before I start blaming thermostats and radiators.

My logic here is given that water boils at higher temperatures when under pressure, this lower pressure cap releases the water at a lower pressure and allows flow to the overflow too soon. This means the water boils sooner than it should.

Can anyone give me ideas on where to get a 110kPa cap that will fit this radiator? Obviously I can try suzuki but I've found the service from the local place to be useless (just don't call back).

[hutchwilco]

For reference, I replace the 0.9bar nissan cap with the manual specd 1.1 and overheating has essentially gone.