How generic are radiator caps?

[xX-Alex-Xx]

Got home from an hour's ride to find the bike had pissed a small amount of coolant onto the driveway. Had a look at the overflow tank (which is behind the sump) and it was beyond full. Dropped back down to half again after the bike cooled so I suspect the radiator cap (either that or the bike knew I was thinking of changing the coolant soon anyway so decided to help )

Trouble is I can't find a new cap (in the UK) specifically for the GSR-750. Any ideas what other models of zook would be ok ... I'm assuming they're fairly standard across the range.
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DILLIGAF

[stinkwheel]

Can also be a symptom of a head gasket leak. Feel one of the radiator hoses as you rev up the engine. If it goes hard, you have a problem.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[xX-Alex-Xx]

[jeffyjeff]

I have used a STANT 11233 successfully on Kawasaki EX500, Honda PC800, and Honda VFR800. See if you can find the OE part number and google "radiator cap cross reference". I'm pretty sure you can find an acceptable fitment right in your local auto parts store. Beats paying a premium for the OE cap, and once you find an aftermarket part that fits, replacement will always be readily available. If I had your Suzuki, I would not hesitate to try the 11233.
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History shows again and again how nature points out the folly of men - BOC

[xX-Alex-Xx]

Looks like the rad cap so far. No extra pressurisation of the pipes when revved, and the coolant reservoir only raises when the bike is hot. New one on order so fingers crossed... Good excuse to get another Gixxer thou if not
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DILLIGAF

[Fizzer Thou]

Test the original radiator cap in a pan of water

Suspend the cap in a pan of water and slowly bring it to the boil.If the cap spring mechanism functions as the water gets warm then it will indicate as faulty.

The same procedure is used for testing a thermostat.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[xX-Alex-Xx]

It's pressure operated (16psi), not temperature. Putting it in boiling water is just going to get it warm.

Need a pressure tester to see it's actually working, but a new cap is way cheaper.
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DILLIGAF

[DJP]

The symptoms that you describe are typical of rad cap failure on Suzukis in my experience.
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Suzuki Bandit 1250
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That's http not https

[WD Forte]

[jeffyjeff]

Boiling point increases by 1.67 degrees C (3 degrees F) for every 1 psi. A 4 psi pressure cap raises boiling point at sea level to 106.67 C (224 F). A 16 psi cap raises boiling point at sea level to 126.72C (260 F).
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History shows again and again how nature points out the folly of men - BOC

[xX-Alex-Xx]

Service manual states 14-17 psi for the cap.
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DILLIGAF

[WD Forte]

Not for my 1959 Morris Minor it dont !!
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bikers smell of wee

[xX-Alex-Xx]

[xX-Alex-Xx]

New rad cap sorted it. Spring on the old one definitely felt a bit weak compared to the new one (both rated for the same 1.1 bar / 16 PSI).

For my original query, the same rad cap that fits the bike also fits about half the cars in the world from what I've seen.
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DILLIGAF

[jeffyjeff]

[Islander]

[Fizzer Thou]

[Bhud]

Radiator caps are cheap, and you could test to see if it makes a difference to swap one out. However, overflow being beyond full and pissing on the driveway (I've had that before) could just as well be a case of needing to bleed the system (air expands when it gets hot and displaces the coolant), or else needing to unblock something that's blocked. Have a look at the coolant filter, just in case.