K100RS running hot

[Filmcamera]

Hello all.


First the good news - the brick is back on the road and legal again!


New clutch is installed and she seems to be running great.


Now the bad news, while it hasn't actually boiled over the engine runs super hot, either just below the first red line, in it or in the second red line.


I have a manual switch for the fan and it is like this even when the fan is on all the time.  Today I rode on the highway at around 5,000 RPM in fifth gear so around 70mph or so withe the fan on and the temperature gauge was in the red.


I had discovered a leak in the radiator and was told it wasn't fixable so I have brought and installed a brand new radiator which is filled with new coolant.  I also had the engine tuned (it failed to pass the emission test first time) and now the engine seems smooth and powerful and doesn't smell of exhaust etc. but runs super hot (it was running hot before the tune as well so I don't think it is just that it has been leaned out too much).


Could it finally be I am having an issue with the water/oil pump?  Is there way to check?


Any other possible causes I should be checking?

[Ingo]

T-Stat... remove, put in pot with water, heat and check when it opens with thermometer. Install new...

[Laitch]

Nice to know you're still around, Filmcamera!

If your brand new radiator came with a brand new thermostat, do you know the temperature at which it opens? Ingo is on the right track. Water pump problems usually show up as leaks from its weep hole or flat out seizure. A head gasket leak can cause over heating and will sometimes show up as combustion gas in the coolant. Tests can be purchased for that or a mechanic can run a test.

If the Brick doesn't feel unusually hot, the problem actually could be with the gauge.

[Filmcamera]

Thanks for the replies.  I will check the thermostat as soon as I can.


Meanwhile I went for another ride at the weekend and paid extra careful attention to the temp.


It was a warm day (most in in Costa Rica!).  When I started it was in the mid 70's at about 3500 feet above sea level. At the mid point, and slowest, point of the ride it was mid 80's and about 300 feet above sea level before climbing back to 3500 at the end.


I noticed that on a fairly fast (between 40 and 60 mph most of the time) twisty road with lots of acceleration but also lots of braking and coasting that if I changed gear at around 4 -5 k the temp was fine.  However, as soon as I went into much slower section, (20-30mph) the temp started to rise.  Then there was a mid speed steep extended twisty climb (average 30-40mph) at the end of that climb the engine was in the first red section.  As soon as I started descending again the temp dropped back to slightly above the half way point on the gauge.  The last section was freeway, again the temp started to rise if I cruised at anything above 5,000, even though that meant I was doing about 80mph.


So it seems I can draw a couple of conclusions.


1. Air cooling if very important, if there is decent airflow the engine is fairly happy.
2. High rpms, or high engine load, push the temperature way up.


I am not sure if that helps diagnose the problem but at least it gives me some guidelines of how to ride around it.


BTW when it was in the red zone I could definitely feel more heat coming from the engine.

[Laitch]

What's the fan doing during these various struggles? Is there any boil-over? Don't dawdle on checking at which temperature the thermostat opens. Speculating right now is futile.

Bricks are noted for generating heat during exercise. You should have experienced discomfort before now. Maybe you should strip down to a wife-beater, a thong and huaraches, or are those your usual riding togs anyway?

[Filmcamera]

The first time I took the brick on a long ride, 6 hours or so in one day, I had blisters on my left thigh the next day from the heat!


I did manage to buy a used heat deflector which helped a lot!


While not an ATGATT person per se I do use boots, gloves, a helmet and some sort of riding jacket.  I long ago accepted that riding in CR means being I will be hot most of the time!


The fan is on 100% of the time, I have installed a manual switch to allow me to turn i on or off whenever I want.


No, there has not been any boil over yet, so it is hot but not actually boiling, so far.  I find that a little coasting when up to speed will cool the engine fairly quickly if it is getting too hot.

[Ingo]

Could it be low on coolant?

[Laitch]

What you're experiencing is not only engine heat but heat radiating from the fuel in the tank. Martin, a member here, has insulated the fuel rail to lessen its transfer of heat from the engine to the fuel heading toward the tank on return. Verify that the insulation on the underside of the tank is in good shape; otherwise replace it. I use Refectix, fiberglass within quilted aluminum covers.

Some of the riders in tropical Australia mount fuel cool beneath or on the radiator. The fuel gets exposure to cooling air before returning to the tank. Mighty Gryphon installed an elegant version on one of his Bricks. Maybe he'll chime in here. Regardless, there's a pictorial of the process in this thread.

[Filmcamera]

Could it be low on coolant?

I did check it and it seems fine, the expansion bottle has coolant in it and even when squeezing the pipe to help add coolant I could get any more in.

[Filmcamera]

What you're experiencing is not only engine heat but heat radiating from the fuel in the tank. Martin, a member here, has insulated the fuel rail to lessen its transfer of heat from the engine to the fuel heading toward the tank on return. Verify that the insulation on the underside of the tank is in good shape; otherwise replace it. I use Refectix, fiberglass within quilted aluminum covers.

Some of the riders in tropical Australia mount fuel cool beneath or on the radiator. The fuel gets exposure to cooling air before returning to the tank. Mighty Gryphon installed an elegant version on one of his Bricks. Maybe he'll chime in here. Regardless, there's a pictorial of the process in this thread.

I actually have a fuel cooler installed but am not sure it helps, in fact it might even make  worse.


Because of the bellypan the only place the cooler fits is hard up against the bottom of the engine beneath the radiator.  I have been toying with the idea of removing it.


The heat proof aluminum insulation of the under side of the tank is in good shape.

[Laitch]

I actually have a fuel cooler installed but am not sure it helps, in fact it might even make  worse.
Because of the bellypan the only place the cooler fits is hard up against the bottom of the engine beneath the radiator.  I have been toying with the idea of removing it.

A fuel cooler should not create more heat, except maybe in the case of yours. Air must flow through or around a cooler. The air can absorb heat from the cooler and carry it away so the cooler is bathed in cooler air. If your cooler is up against the engine, it is likely that air entering the cooler becomes turbulent and stalls between and around the coolers fins. The turbulent air absorbs engine heat and keeps the cooler bathed in heat instead of fast flowing air. The cooling effect of flowing air that is continually replaced as it carries away heat has been negated. The fuel can become even hotter.

The thread with Mighty Gryphon's work also shows other examples of sites for a cooler where air can flow through or around and then past it. Martin insulated the fuel rail and a few other components. Maybe he'll chime in here, too.

Let's get on with testing the thermostat despite evidence that the system seems to be working as designed because the overheat light hasn't been lit.

Maybe a johnny blanket would help.