Gurgling Coolant '91 VFR750F

So the last time I ran my bike after being at idle for maybe 10-15mins my overflow container of coolant begins to bubble/gurgle. It sounds like my fan turns on but the bike still turns runs hot with the gurgling continuing until I turn the bike off. The coolant is full in both the overflow container and the radiator. Now the solution seems to be the thermostat, however if that is not the issue I'd rather not replace the tstat if I don't need to. Any help is greatly appreciated!

 

Radiator caps sometimes go bad and won't hold pressure................ Bikes don't like idling for prolonged periods and most do tend to overheat due to insufficient airflow.

you're doing no good to the engine by idling too long in warm weather. blame yourself in this case, not the thermostat.

 

If it has the original thermostat in it, it should be replaced anyway.

 

https://motorbikewriter.com/how-warm-motorcycle-engine/

 

Replace the cap as a first measure; gurgling and hissing from the overflow would be sign that the cap is not holding the requisite pressure and allowing the coolant to boil at a lower-than-Honda-intended pressure.

 

Thanks guys, this is my first bike and I am still learning all of the ins and outs. I read this forum and found out one of my initial issues was my stator which I am already replacing, bearing shipping time anyway, but I am new to the mechanical aspect of bikes. I will look into the radiator cap first. Is there anyway to test if the radiator cap is bad? Or is it just a get a new cap and hope that's the case kinda thing and if that doesn't fix the issue try something else kinda thing? Again appreciate the help and advice!

 

It isn’t easy to test the cap, but it won’t be expensive to replace. Easiest would be a genuine cap but you should be able to find a suitable unbranded item at an auto parts store.


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And if the cap happens to not be the issue, is there a way for me to test the T-stat? Or is that another one of those things where I just need to replace it and see if it makes a difference or not?

 

if you get to the point of 'having' to test it - then replacing it IS THE ONLY OPTION.. lol

Basically, testing a 'cheap' part when you have gone to the trouble of removing it seems rather pointless..
By all means, stick it as a spare - it is fairly easier to ck, BUT put a new one in..

 

& its pretty much the same with spark plugs - if you have to pull them, replace with new, clean them up & place in the tail of the bike as emergency spares...

 

You can test the function of the thermostat by the way the radiator heats from cold. If the tstat functions correctly it keeps coolant circulating in the engine only until hot, then releases that to the radiator. So if you start from cold and keep your hand on the radiator, the radiator should stay stone cold until the gauge creeps to about 1/4 then you should get a sudden (and noticeable !) increase in radiator temp as the hot coolant starts flowing there. If the radiator starts heating slowly from the time you start the bike, then it is stuck open. If it never heats up, it is stuck closed.

Or you can pull the thermostat out and dunk it in a pot of water on the stove (when your wife is out). You can visually see the thermostat opening or closing in response to temperature (should open at around 80C). Here's one I cooked earlier:

 

Appreciate the help again guys, I'm gonna check the tstat via the quick test method when I get my stator back on later his week and I'll go from there!