Rocket 3 Roadster Possibly Overheating?

atomsplitter said:

Yes, top up and seal up and you're golden.

A bit of understanding of your cooling system might help here. Water is the actual coolant because it has a very high specific heat capacity (symbol cp). If you raise the temperature of water to 212F it achieves 'saturation' meaning it can't hold any more heat without going thru a phase change. The amount of heat to change one pound mass water to one pound mass of steam at 212F (at atmospheric pressure) is 970 BTUs. That's a lot of BTUs (a BTU is defined as the amount of heat required to raise the temperature of one pound mass of water by one degree Fahrenheit at about 60°F). It's called the "latent heat of vaporization" and it's how the heat in your engine is moved from where it's produced in the combustion chamber to atmosphere flowing across the cooling fins of your radiator. Once water at atmospheric pressure reaches saturation adding heat will NOT raise its temperature, only vaporize the mass faster. One gallon of water has 8.34 pounds-mass so if your cooling system holds a gallon of water, it has the potential to hold 8090 BTUs circulating in the system. As you raise pressure on the water the BTUs it will hold goes UP before boiling occurs. That's why the cooling system of your motorcycle has a pressure relief cap to increase the total BTUs the system can remove effectively from the combustion process to atmosphere. To understand how your system was designed you need to know the heat load and how much has to be removed to maintain material properties desired (too much heat expands metal beyond operational limits). You can arrive at that heat value by calculating the total heat of the fuel burned per hour at full throttle for the maximum heat load. The cooling system can then be designed to remove that heat load plus an added safety margin of say 20%. To calculate the size of the heat exchanger needed (radiator) the engineers use that heat load value and how much air differential temperature is needed. That leads to how much water flow is needed to move those BTUs so the result is: Rate of Heat is equal to the mass flow rate times the differential temperature of the source to heat sink.

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I’m gonna call you professor! lol believe it or not I appreciate the explanation truly. Wish I had this additional knowledge growing up. Instead I’m all computers and video which I love

You're welcome.

Also the Stant cap is available on Amazon for order:

buddazero said:

I’m gonna call you professor! lol believe it or not I appreciate the explanation truly. Wish I had this additional knowledge growing up. Instead I’m all computers and video which I love

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Atomsplitter is fine. I was a licensed nuclear plant operator and then senior licensed power plant instructor teaching plant systems, procedures and operations. Like I said I have a head full of stuff that needs vented from time to time. Passing on the knowledge is a treat when someone wants to learn.

I’m someone who wants to learn everything even though I may not understand it right away lol I’m more of a hands-on person so being hands-on with my bike is definitely helping me to learn faster.

If I had someone like you in New York, I would literally take my whole bike apart just to put it back together just so I can learn everything

buddazero said:

I’m someone who wants to learn everything even though I may not understand it right away lol I’m more of a hands-on person so being hands-on with my bike is definitely helping me to learn faster.

If I had someone like you in New York, I would literally take my whole bike apart just to put it back together just so I can learn everything

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Well, I'm available to solve your mechanical mysteries whenever you have a need, I retired in 2017. I do spend time riding my bikes so please be patient for an answer, but feel free to DM me with specific questions whenever you need.

atomsplitter said:

R-III-R Turbo is correct. The 50-50 mix is to ensure the cooling system does not freeze in extreme low temperatures. In the summer you could run a very low mix of antifreeze in the system to prevent corrosion, and it will be fine. ​

Any coolant you buy off the shelf is typically a 50-50 mix of distilled water (evaporation process) or demineralized water (resin bed filtration process). The water is what actually does the cooling, so having more water than antifreeze makes the cooling system more efficient. Maximum efficiency would be 100% demineralized water alone in the cooling system, however there is a tradeoff for going that route. The anti-freeze component of the coolant mix provides corrosion inhibitors and has pump seal lubrication components in the fluid. Using only water would allow corrosion to build up in the system and could damage water pump seals. So, adding more water than anti-freeze has only one small drawback and that is reduction of the freeze protection in winter. If your winters are mild (rarely gets below 10F) you are probably safe since the freeze protection limit is stated on the bottle is -35F. Here in North Texas a 50/50 mix is overkill. If your area never gets that cold (-35F), then a 60/40 or 70/30 mix may be fine. To verify your freeze protection is within limits you can purchase a hydrometer to see what your coolant protection level is for about $5.00 at any auto parts store. Be sure to run the bike for a few hundred miles to ensure a few cycles through the expansion tank so the mix is homogeneous and you are good to go. If the protection isn't quite enough, add some straight antifreeze to the expansion tank and ride a few hundred miles and test again. You'll eventually get the mix and protection limits you want.

You can order a coolant tester from Amazon for about $5.50. To test your coolant, you draw up a sample from the radiator, and the pointer will indicate the protection temperature of the sample. You can return the sample to the radiator when done.

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Antifreeze along with pressure also raises the boiling point inside cooling system, so 50-50 mix is beneficial and practical.

Gerald said:

Antifreeze along with pressure also raises the boiling point inside cooling system, so 50-50 mix is beneficial and practical.

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Absolutely true. The saturation temperature of water is pressure dependent. From the steam tables you can get a correlation between temperature and pressure:



The pressure cap maintains the system at a maximum pressure since it's a relief to the expansion tank. The OEM cap specifies pressure at 1.2 Bar which is equivalent to 3 psig (or 17.7 psia), The above table can be interpolated to about 222F at that lift pressure. The reason the water temp is allowed to slightly exceed that temperature for a short period (temperature above 222F raises pressure above 1.2 Bar lifting the cap) is to drive off water in the oil system since it operates from atmospheric pressure at start-up to slightly below atmospheric pressure (crank case ventilation system) under load. As the thermostat opens and cooling increases from added water flow through the cooling tubes in the radiator, cooling system pressure drops closing the radiator pressure cap relief to expansion tank. Any water in the oil comes from the combustion process (assumes water pump seal not leaking) and is a detriment to engine internals as it's lubricity and friction resistance are incompatible with engine internals. The thermostat in the cooling system is there to ensure the oil is heated as quickly as possible to drive out the water and the crank case ventilation system continues to vent moisture from the crank case to airbox through the crank case vent. The airbox is maintained slightly below atmospheric pressure by the piston intake strokes, so the boiling point of water is less than 212F in the crank case and any water vapor is vented to the airbox. The cooling system operates as a heat exchanger to support engine operation at higher power levels. (when under load). If the engine had been designed to operate at 40 or 50 HP it could be air cooled and no water needed for added cooling (i.e. how many vintage motorcycles have water cooling systems?). While it adds a layer of complexity to system operations the cooling system on new bikes is to permit higher power limits for a given displacement. Big power means big heat and the cooling systems are designed to dump that excess heat to atmosphere.

Any update on the overheating issue?

atomsplitter said:

Any update on the overheating issue?

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Trust me, I plan to update. Thanks for checking back!

My torque wrench and the correct bolts was delivered, as well as the proper coolant coolant so I don’t need distilled water anymore. All I’m waiting for is the god**** pressure cap to arrive lol

I ordered the one from Amazon that you sent me, but I won’t be here till Saturday, but maybe the pressure Triumph pressure cap I ordered will come first? Either way I’m just waiting, haha!

The pressure cap from AutoZone that I sent you seems that it would do the trick, but I’m not taking any chances so I don’t mind waiting.

buddazero said:

Trust me, I plan to update. Thanks for checking back!

My torque wrench and the correct bolts was delivered, as well as the proper coolant coolant so I don’t need distilled water anymore. All I’m waiting for is the god**** pressure cap to arrive lol

I ordered the one from Amazon that you sent me, but I won’t be here till Saturday, but maybe the pressure Triumph pressure cap I ordered will come first? Either way I’m just waiting, haha!

The pressure cap from AutoZone that I sent you seems that it would do the trick, but I’m not taking any chances so I don’t mind waiting.

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You won't need three caps so it's all good, just was curious how it was coming along.