TOPIC:

So maybe I should consider a 7 blade fan then or a more powerful aftermarket one.
The fan cuts in a little before halfway, the non original temp switch came from Canada if I remember rightly and was meant to cut in before the standard one but actually if anything cuts in later, not good. Having said that the engine got hot before but something has happened since the rebuild that makes it get REALLY hot.
Maybe having a manual switch might help but can't help but think in heavy traffic and the 30+ air temps we have here in summer it's still going to get too hot eventually. Once the engine is off the fan goes for ages, stops and then with heat build up comes on at least twice more. Good job I've got a good battery,,

Petez13 wrote: Ive checked the fan and it's blowing the direction it should, the rad was flushed through and externally is not jammed up with bugs etc.
Is there a way to check the stat is working? I guess the bypass pipe should be hot while the rad is cool until the stat opens.
Is there any advantage with the 7 blade fan? Or won't it make much difference?
Just another idea to try and cool things down, especially with our hot summers.
Btw, I've just ordered from ebay a bottle of water wetter.

Thermostat testing is described on page 206 of the manual.

Page 202 of the Service Manual has a circuit diagram of the coolant flow and as you can imagine if the thermostat does not seal in bypass or in circulate position them the coolant flow is disrupted. It's really important that the valves in the thermostat are functioning properly. Also note, that when this type of coolant circuit is working properly you can see the temperature swings on the temp gauge. When you first start up the bike from cold and start running the bike, you can watch the temp gauge rise until the thermostat opens, then the temp gauge should swing downwards indicating the cool coolant has transferred from the rad to the engine. Then the temp starts rising again until the engine coolant has reached the opening temp of the thermostat, then the thermostat opens and you should see the coolant temp drop again indicating another exchange of coolant from the rad to the engine.
So how to interpret what you see. lets say you witness the first cycle of coolant and you see the temp rise and then a drop in temp. That's good, you can assume that the thermostat is closed properly on bypass while the engine temp is coming up and then opening properly and recirculating the coolant from the rad. All good.

What if on the second , third, or fourth cycle, you notice not so much of a drop in temp. It's important that the coolant in the rad stays in the rad and gets a chance to cool the coolant. If the coolant stays in the rad and the rad coolant tubes are blocked then there's little or no heat disapation, then when the coolant cycles you won't see a temperature fluctuate. The other scenario is that if the thermostat does not close properly, then the coolant doesn't stay in the rad to cool but is constantly recirculating picking up more and more heat until you finally say "time to pull over and let it cool off"

Your question about a 7 blade fan- Will it flow more air? Yes it will. I made the modification just because I could and it's described in my post "Kawboy's conversion of a B2 to an A2" if you wish to see what/how I did it. Do I believe it's a necessary modification? Absolutely not. If there was an overtemp problem with the design, Kawasaki would have come up with a recall or changed the design in the early years. There never was a change in the fan design over all of the years of availability so this substantiates my belief that it's not necessary. If you have an overheating problem it's a problem. Fix it. Don't put a band aid on it. Always, always, always go back to basics. Understand your problem come up with a fix, execute the fix and monitor for change. Once you start bastardizing your systems you tend to create other problems. Changing fundamental designs usually wreaks havoc. I'm a firm believer in the KISS principal- Keep it simple stupid. If you assume all operating problems are a design problem you'll over complicate your issues to the point that your modification create other problem and now you have no idea what the real problems are.

I hope this helps with your issues.

KB

Petez13 wrote: So maybe I should consider a 7 blade fan then or a more powerful aftermarket one.
The fan cuts in a little before halfway, the non original temp switch came from Canada if I remember rightly and was meant to cut in before the standard one but actually if anything cuts in later, not good. Having said that the engine got hot before but something has happened since the rebuild that makes it get REALLY hot.
Maybe having a manual switch might help but can't help but think in heavy traffic and the 30+ air temps we have here in summer it's still going to get too hot eventually. Once the engine is off the fan goes for ages, stops and then with heat build up comes on at least twice more. Good job I've got a good battery,,

As Kawboy says, without discovering the cause, all of these suggestions are just putting a bandaid on the problem. It still exists whether you use water wetter or a 7 bladed fan. The point is your engine shouldn't be getting hot enough to require these fixes. These things can be used to lower your operating temperature when you are operating in extremes like hot traffic in very hot weather but your bike shouldn't overheat under normal use.

You've established your fan is coming on and its turning the correct way. You are pretty sure your rad is clean. That's a good start. I would explore the thermostat as the next likely culprit. Just because it was new 6 mos ago doesn't mean its working properly now.

If you just put the bandaid on it then it will come to a head very quickly at some time. Because you said that when it gets hot it doesn't cool quickly when the load comes off then that is very typical of a radiator not flowing correctly, either because of the bypass not closing off or a blockage.

Yes it's true I need to find the root cause, it looks like the stat will have to be taken out and checked. I think thats done by putting it in a cup of boiling water. I did see movement with the engine running while the rad cap was off but maybe not enough.
Should the coolant flow be obvious, I had to get a friend to lean the bike over to the right before I could see the flow last time.

Have you checked the cap itself? An improperly sealed system will cause your engine to boil over faster since the pressure keeps the coolant from boiling sooner. There are caps that will raise the pressure so the boiling point is higher.

Are sure you are not leaking coolant elsewhere, especially into the oil? If you have a dud head gasket that can cause overheating, not too mention coolant in the oil which can eventually take out your bearings by pitting them.

Yes, you can test the stat by placing it in a pot of water with a thermometer. The stat will have a specific temp where it is supposed to open. As the water comes up, see if it is opening at the right time. Also see if it closes when the temp goes back down. I'd try cycling it a few times to make sure it works consistently.

Make sure you clean all the coolant out of the stat and thoroughly wash the pot and thermometer. Coolant is poisonous but you already knew that.

If that checks out, The only thing I could suggest is checking the water pump and maybe a pressure test. I've not had much experience with cooling problems so I am running out of ideas.