Boiling gas – Overheating – Weep hole 70 degree motors 2010

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Thats good to know. I had my '09 450 boil the gas on the trail after some moderate bush wacking on a cool day.
The bike barely ran, it was not a pleasant experience on my first trail ride. I have since added more insulation to the pipe, but connecting the fan to blow all the time could be a quick fix if I do boil the gas again.

Just remove the connector from the switch in the rad and ground it somewhere. Maybe I can add a tab that can be used for this.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

A photo would help.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Yes, this site is a bit challenging when it comes to posting photos. Thanks for making the attempt!

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

to add a photo all you need to do is use the "Img" button that is in the middle of the grey buttons above the text box to insert where you want the photo to appear

then just copy and paste the address of your photo between these

the only issue is the photo you load has to already be uploaded to the web be that on a social networking site, a photo hosting site or even in the gallery here.

its really rather simple.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

If you want the fan to run more often, just get the 85C thermo switch, instead of the stock 100C switch.

It may also be that your thermo switch is not right, meaning the contacts are not closing at 100C, put it in a pot of water, use a candy thermometer and bring the temp up slowly checking the switch to see when it closes. 100C = 212F.

With the fan/thermo switch functioning properly, your 390 should not be boiling over.

Another thing that could be wrong is that your rad cap is weak. If you can get it checked.

I agree that the fan running more often will help keep things cooler, and will in turn help keep the gas from boiling.

Have you had the ECU reflashed to the competition map? That helps a lot with keeping engine temps down.

As well, opening up the air box like I did also allows a lot more cool air from above the motor in, and helps keep engine temps down as well.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Dale,
I think you're onto something important with that thermo switch for the fan. Are only 100C and 85C switched available, or is there a range of switches? Do you know where to go for part numbers?

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Ruger said:

Dale,
I think you're onto something important with that thermo switch for the fan. Are only 100C and 85C switched available, or is there a range of switches? Do you know where to go for part numbers?

Click to expand...

Just look up the fan kits for the last generation bikes.........they came with the 85C switches, but, everyone wanted the 100C switch to keep the fan from running so much b/c it drained the battery, b/c, there was only 25W of DC power going to the battery. I did a stator rewind from SPARKS on my 04, and rewired that bike to run on all DC, SPARKS rewind put my stator output at 120 watts with a lower primary voltage, as compared with the standard way of just floating the neutral.

On the new bike, 09-, everything goes to the battery all 200 watts, so the fan running all the time is not a problem.

I'd check and make sure that switch is functioning normally first then proceed.

The 85C is = to 185F, I looked at the parts book for the current gen bikes and it does not indicated what temp the thermostat is. But, the old switches used to have the fan running most of the time.

Keep in mind that you need to keep at least 180F on the water jacket around the cylinder for proper ring sealing.

I don't know if the switches come in anything other than the 85 or 100's. 100 C is 212F and really should be sufficient to keep the coolant from boiling under the 1.8 bar cap.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

You're welcome Todd, and thank you for the compliment!

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Another fan switch option is available for around $20 from NAPA, Altrom Imports part number ATM 1435033. The switch is 95/90C and works a peach. Per my trail tech temp gauge, the water temp coming off the head is 203F when the fan comes on, vs. about 223F (again, temp read from the head) for the stock one. The fan runs more, but not all the time.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Dunken, that's the middle ground option I was hoping existed.
Brilliant!!!
Do you have the NAPA part number, please?

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

I did a bit more checking...........

I believe the stock thermostat opens at 70*C = 158F.

Keep in mind this is the temperature of the coolant coming out of the motor after it has made its full pass through the motor.

So depending on the coolant flow rate, which is proportional to the engine RPM, and the amount of air flowing over the radiators, will depend on how much heat transfer the coolant gets on each pass through the radiator.

One of the things I found in past with my 04 550, was that to help keep it from boiling over, (before I switched to Evans ) was to keep the revs up a bit when going slow, moving more coolant through the radiator, FWIW.

And FWIW, if you have the ECU flashed with the comp map, it will put more fuel into the motor at any given point, thus lowering EGT's and combustion temps. It is my understanding that when the coolant temperature sensor see's a high coolant temperature, it will begin to richen the mixture to lower EGT's, so if you have the "green" map, the ECU will be not able to deliver as much fuel as the comp map.

Also, by making the air box mod that I talked about, this allows much cooler air to be drawn from the top, instead of its main source of pulling in air from the bottom through the whole where the fuel line goes through. This makes it a submarine, but, also means that you are pulling in that superheated air you mentioned. See the thread here: viewtopic.php?f=7&t=15312 With this mod, you will hear a lot more of the intake noise as well.

This has two effects. First the air entering the motor is much hotter than ambient, thereby raising combustion chamber temps, and therefore overall motor temps.

Second, there is an Intake Air Temp (IAT) in the air box, that, in conjunction with the Manifold Abosolute Pressure sensor (MAP) lets the ECU determine the density altitude, and adjusts the over all mapping of the motor. Air Temperature has a huge effect on density altitude, E.G. if the air is hot, the density altitude is much higher than it would be if the air was cooler, so the ECU delivers less fuel to the motor to compensate. Check this site here to see what I mean: http://wahiduddin.net/calc/calc_da.htm

Pilots use density altitude all the time to determine performance characteristics of the aircraft they are flying, and when I was jetting my FCR I kept track of this information so that I could make jetting changes before I left the garage to where I was going to ride since I ride in some greatly varying conditions.

For instance, when riding at 8500' with a temp of 30 degrees, the density altitude is 8614'. At 95 degrees it goes up to 12,567'. The ECU on your bike is always looking at IAT sensor and adjusting how much fuel is being delivered to the motor, the beauty of EFI, so, in slow going where it is pulling all that really hot air off the top of the motor, it is going to really lean down the mix to keep the motor running clean, plus you have the radiant heating coming from below the IAT from the mid pipe which is directly below it.

This will continue until the coolant temp gets too high, and the ECU will begin over ride the density altitude to richen the mixture to try and bring down the coolant temp.

So, I totally understand you wanting to make the easiest fix, KISS principal right? Keep it simple stupid! I believe that with your fan solution, you will still greatly benefit from the air box mod, and wrapping the mid pipe when you have time. The air box mod will yield noticeable performance results as well.

One other thing that a mechanic friend of mine showed me is that every once and a while, pull the radiators off after you have washed the bike, and lay them in a tub of water with dish soap overnight. You will be amazed at how much more crap comes out of the cooling vanes. If you look closely at the vanes between the radiator tubes, you will see that there are small louvers in the vanes to increase the surface area of these vanes, or heat sinks. These little louvers get full of crap and regular washing you give your bike will leave these louvers clogged.

I know this is a lot of "stuff" but I've spent a lot of hard learned lessons learning all this stuff, and in the end the cumulative effects are substantial.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

Dale, lots of good info there. Sorry for the slight hi-jack but my FX doesn't have a thermostat. I have my TT voyager temp sensor on the return hose back to the radiator. with any air flowing at all I thought (good excuse to go for a ride) that my temp was showing under 180 all the time.

I have the FX (2 stroke also) fan but I have not installed it yet. the instructions show putting the temp sensor in the short hose going to the water pump. wouldn't it be better to have it on the return also, sort of give it a head start? the stock temp switch would probably be fine on the return but a lower one seems smart on the cool hose.

What is the lowest temp switch you would recommend running?

I also just got back my FMF megabomb that has been ceramic coated by performance coatings, that should cool things a little also.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

UPSguy said:

Dale, lots of good info there. Sorry for the slight hi-jack but my FX doesn't have a thermostat. I have my TT voyager temp sensor on the return hose back to the radiator. with any air flowing at all I thought (good excuse to go for a ride) that my temp was showing under 180 all the time.

I have the FX (2 stroke also) fan but I have not installed it yet. the instructions show putting the temp sensor in the short hose going to the water pump. wouldn't it be better to have it on the return also, sort of give it a head start? the stock temp switch would probably be fine on the return but a lower one seems smart on the cool hose.

What is the lowest temp switch you would recommend running?

I also just got back my FMF megabomb that has been ceramic coated by performance coatings, that should cool things a little also.

Click to expand...

Hey there UPS,

Good question.......If you put on a 85C switch, which is equal to 185F your fan is going to be running a lot. However, you have the stator to run it that way, and you should not have a problem with battery charging. As the original poster said, having the fan running all the time cured his boiling gas problems as well as his boil over problem.

As mentioned before, on the old bikes that didn't have enough power dedicated to charging the batter/running the fan the battery would go flat with the 85C temp switch so everyone wanted and went to a higher temp level switch.

Personally, I am going to leave my 100C switch in place so the fan doesn't run all the time. My 570 only recently boiled over during the National Hare & Hound I raced a couple of weeks back, but, it was around 110* in the canyons, and 100* when the race started I was using my clutch a lot, and I am pretty sure that the radiator cap had given up the ghost and was lifting at a lower pressure than it was supposed to. I'd like to add a second fan to it, and probably could, but, for the reasons above, I have not really pursued it.

The reason I'm pretty sure of this is b/c a week later I had my bike idling in the garage for a while, and the fan normally will cycle on and then off while it is idling with no problem. However, this time it boiled over with the fan on. I took the cap off of my other/newer 09 and put on the one that was boiling over and no more problem. This is the second time I have had a radiator cap go bad.

All that being said, I have run my original 09 through some pretty brutal stuff, and the fan was running all the time, and there was never a boil over. That is why I suggested to the original poster to have his cap checked as a 390 should not boil over with a fan on it, UNLESS, you have it some pretty harsh conditions. Could also be the thermostat.....not sure if I mentioned checking that or not.

However, on your bike, you just want to keep it from boiling over, so I'd go with the 100C switch, which I believe comes with the kit?

One needs to keep in mind that you want to have a certain amount of heat in the motor. The bikes that come with a thermostat, have the stat open at roughly 160 on the output side of the radiator, as I mentioned before, the amount of heat that is transferred to the air is dependent on coolant flow rate and the heat transfer capability of the radiator AND the coolant. Otherwise know and Delta T. Coolant like Evans do not boil until 370 at zero psi, however, their heat transfer rate is much less than regular ol' Ethylene glycol / distilled water. The advantage of Evans of course is that it stays in the cooling system, even if the motor runs 15-20 degrees hotter, and runs at zero pressure.

Re: Boiling gas – Overheating – Weep hole 70 degree motors 2

I was concerned as you said in an earlier post that you needed to keep the water in the jacket over 180 but i'm hardly ever seeing that in normal riding according to my TT gauge measuring temp as it exits the motor.