Oil temp, Coolers, and oil opinions

[martysgone]

I just got back today from 7 days/800+ miles of the UTBDR on my stock (mechanically) bike. I wanted to post some opinions and observations on oil temps. Before leaving I installed an Opmid multimeter that takes oil temp from the stock sensor. Realize that this is the hottest point you can take measurement, but I believe that is the most valid measurement.

Riding in 100+ temps I would typically see temps above 320F. Once I climbed to altitude the temps dropped (80's?) but the climbing and thin air kept me in 2nd gear a lot of the time. This is where the temp would really rise. I could easily hit temps in the 370F range and would stop to let the bike cool. Once I got back to SLC driving in traffic it would often hit 300+ in summer heat.

I have heard it said that stock motors do not need an oil cooler. This may be true but I would credit it to the quality of the machine and would still argue that they get too hot under the conditions I ride in. Which leads me to these conclusions: Only use synthetic oil designed for motorcycles. Conventional oil cannot handle the heat these little work horses generate. Secondly, if you do any serious overlanding or high mountain trail riding an oil cooler seems to be a necessity. I used synthetic oil and will change the oil tomorrow even though it has only seen 800 miles. I will also not go on another long adventure like that without an oil cooler to ease my anxiety.

Now, what oil cooler for a stock cylinder???

 

[NMCoyote]

oil coolers do some good with the temps but is now potentially a source for road damage failure depending on where you put it. For it to work the best it would need to be the coolest air flow available, but then that also exposes it to damage.

 

[NMCoyote]

and Dinosaur oil displaces heat better then synthetic oil, just sayin! Synthetic oil holds up to higher friction pressures created by very tight tolerances in modern motors better but does not displace heat as well. And the Honda engine in these just don't require the cost of Synthetic oil or the lubricating properties of a high performance engine.

 

[dmonkey]

You could mount an electric fan for active cooling to the fins

In all seriousness, I've ridden my CT125 quite a bit in the mountains and summer heat without real issue (just some oil consumption) using Honda's GN4 10w30 conventional oil. It's a simple, cost effective, and reliable engine design that is tried and true for a wide range of real world riding situations. The stock bike doesn't need an oil cooler or different oil, but it certainly could benefit from them as almost any air cooled engine could. As @m in sc has mentioned elsewhere on this forum, the stock oil temp sensor gets oil splashed on it which doesn't make it a reliable data source. If you want consistency in oil temp readings for comparison under various operating conditions, you may want to mount an oil temp sensor elsewhere on the engine. You can also change the oil more frequently if you're worried about it cooking and degrading.

With the stock cylinder and head you might be able to run a kit like this if you want to add an oil cooler:

Morin Racing Oil Cooler Kit - Grom 13-20 Models - TBparts.com

The Morin Racing Oil Cooler Kit for the Honda Grom (and MSX125) is a high quality accessory designed to help the Honda horizontal engine run cooler.

www.tbparts.com

That kit is for a Grom so expect that it may require some modification to fit and mount on the CT125.

 

[martysgone]

Dino oil breaks down at 300F or lower so I am unwilling to run it during the summer. Our little motors can hit that easily on a hot day. Good synthetics can handle that heat. Dino oil may dissipate heat better but not enough to keep our motors below 300F when they are pushed in hot conditions. You don't fry food with olive oil. And I definitely agree, changing your oil more frequently when you are riding them hard is cheap insurance. But we all get to decide what we think is best for our machines .

 

[Cpd419]

I’m changing to Honda full synthetic next oil change. Probably don’t need to but I bought 3 quarts and that’s what it’s getting.

 

[dmonkey]

If this engine's temps were cooking the recommended conventional oil it likely would have been observed a long time ago with the Honda NF series.


OPMID product notes about the temp sensor:

Displays the measured value of the genuine temperature sensor. The displayed value is the same as the output value to the OBD2 tool.
A genuine temperature sensor is attached to the passage where the oil that has become hot in the cylinder head returns to the crankcase. Since it is measured at the hottest point, it always means a value higher than the average temperature of the whole oil and the drain bolt temperature at the bottom.
In addition, since the discharge amount of the oil pump increases or decreases according to the engine speed, it refers to a value close to the temperature of the hot oil during running when the circulation amount increases, but the running wind does not hit and the oil circulates. When the vehicle is stopped (during idling), the amount of heat generated> the cooling power, and the value of the genuine temperature sensor near the combustion part starts to rise immediately.
In addition, CT125 has an average engine temperature of about 15 ° C higher than Monkey 125 due to the fact that the total amount of oil is about 20% less and the frictional heat of the centrifugal clutch.
Reference value) Temperature around 20 ℃ ・ Normal engine
Monkey 125:
110-115 ℃ while driving, 120-125 ℃ while stopped
CT125:
125-130 ℃ while driving, 135-140 ℃ while stopped
“Stopped” for several minutes It is the value of waiting for the signal of, and it rises as it stops for a long time.
As an option other than using a genuine temperature sensor, the multimeter is equipped with a reading circuit that can also be used with a retrofit temperature sensor. A drain bolt type temperature sensor common to Monkey 125 and CT125 will be released around the spring of 2021.

These notes are likely for the JA55 rather than the JA65 (2023) model which is higher compression but also has an improved piston oil jet design.

 

[m in sc]

when i put in the over sized oil pump i increased the orifice in the case dowel to almost 2mm to feed the topend. would recommend. no issues and it flows like crazy up there. been like that for about 1k. that cooler will fit, mount it high though. thats where i had mine on the grom and it never saw damage. (mine was a 5 row though)

 

[AZ7000']

I would guess the conditions you have in the summer are pretty equal to Southeast Asia in their hot season, but more humid there.

I don’t think it’s a precision instrument, more of a daily driver workhorse. Enjoy whatever path you choose, I’ll bet the stock engine survives either way.

 

[martysgone]

Yeah, they will survive. I think of the crazy abuse I put my old 90's through. I was doing idiotic treks on them long before I dreamed they would reinvent the CT's. Reading through too many forums it seems the common denominator with destroyed engines is either bad fueling or ridiculous rpms. But I don't think my conditions are entirely equal to SE Asia because of the altitude. Where I saw my temps really spike was at 9,000 feet and higher asking the poor thing to climb steep hills it could only hold in 1st or 2nd gear with 40 lbs of camping gear. If I can do anything to minimize my guilt for treating it that way, I will. How much more is it to buy a single quart of synthetic. And I do plan on an oil cooler for mine but will leave my wife's stock. As long as it gets hot enough to cook off condensation, I can't see a negative to it. But I do agree these things can take some abuse!