Engine Temp

[Dia1Up]

Well now that the riding season is over here in Canada.... Mod season as begun


This is my first motorcycle, and even more important, first air-cooled thing. I live in an extremely hilly area. 1st and 2nd gear up steep hills for periods of time (like the trail near my house) the engine gets really hot of course without any sort of speed to get some air flowing. Originally I was getting some good amount of pinging. I switched to 94 octane no ethanol, and that has helped massively, but there is still a touch of pinging. I swapped to a colder plug, also helped a bit too. The ping was mostly gone, but could still creep up on particularly hot days. I changed my oil before winter storage, which was 10w-40 full synthetic and replaced with the same 10w-40 synthetic, but even after only 1300km it was looking fairly cooked. So now I'm wondering if I want to spend a bit of money on a few fooling mods like a finned filter cover and valve covers for a bit of extra surface area


Oil temp gauges are hilariously over priced, but the question is what head temp should I be looking for?

Easy to measure with a little infrared reader. I imagine air cooled engines have a very wide range that comes with the nature of course

 

[dmonkey]

Any mods to the engine, or stock? If ethanol gas is available, it should run cooler. Unless you're putting the bike in long term storage, ethanol really isn't going to hurt it.

 

[m in sc]

ethanol inhibits detonation as said. Ive been running the corn squeezing's for many years, its fine. just run the bike every once in a while. just spend and get the opmid, i had one on my grom and it was great. however, on a stock bike really isn't needed. define 'hot'. all air-cooled motors run 'hot' as they have to obviously shed heat. you can run a colder plug to reduce combustion chamber temp at high rpm as well.

some info from the grom guys below as far as oil temp gauges.

Oil temp gauge (cheap and effective)

Could someone point me in the right direction. I've been looking all over and cant seem to find what I'm looking for. Every gauge I come across when I search for oil temp gauges ends up being cylinder head temp. I've found the tto oil temp gauge but cant seem to find an adapter to run it in the...

www.hondagrom.net

 

[BergyPatty37]

You could look into an oil cooler install. Will increase the oil capacity (very slightly but still) and cool the oil. I know some of the folks on here have done that, usually in conjunction with big bore mods.

 

[dmonkey]

Also if you're comparing temps, keep in mind that temps from other models and generations of engine won't be an apples to apples comparison, just a general reference. The semi-auto bikes run hotter than the full manual bikes due to lower oil volume (0.1 US qt or 0.1 L per the owners manual's spec for oil capacity after disassembly for the latest engine) and more friction from the centrifugal clutch, but the Euro5 engine redesign on the JA65 has improved oil delivery to the top end which should improve cooling there. The stock JA65's engine has better options for adding an oil cooler than the earlier JA55's engine if you do go that route.

 

[Dia1Up]

Any mods to the engine, or stock? If ethanol gas is available, it should run cooler. Unless you're putting the bike in long term storage, ethanol really isn't going to hurt it.

Bone stock 2025

 

[Dia1Up]

ethanol inhibits detonation as said. Ive been running the corn squeezing's for many years, its fine. just run the bike every once in a while. just spend and get the opmid, i had one on my grom and it was great. however, on a stock bike really isn't needed. define 'hot'. all air-cooled motors run 'hot' as they have to obviously shed heat. you can run a colder plug to reduce combustion chamber temp at high rpm as well.

some info from the grom guys below as far as oil temp gauges.

Oil temp gauge (cheap and effective)

Could someone point me in the right direction. I've been looking all over and cant seem to find what I'm looking for. Every gauge I come across when I search for oil temp gauges ends up being cylinder head temp. I've found the tto oil temp gauge but cant seem to find an adapter to run it in the...

www.hondagrom.net

I was running 91 with 10%, switched to the fancy 94 ethanol free which helped with the pre-ignition, 1 step colder plug helped as well. Still some ping. It's also worth noting the gas station here has a dedicated pump for the 94, with as small as the tanks are on these little bikes, I have to wonder even if you choose "91" on the normal pumps, how much actual premium ends up in the tank. Regardless, seems odd a basic little bike needs fancy gas in my mind


Not sure on actual temp, not sure. But hot enough to ping once warm.


It may not be temp, but the symptoms of ping when warm, reduced with higher octane, and slightly reduced a bit more with a colder plug. As well as (I think) more cooked oil than it should be, is telling me too hot. Sadly even searching Groms, not a whole lot of info, these engines tend to be completely bullet proof for the most part



(Side note, everything I can find online regarding ethanol, it seems to make engines run hotter oddly. Although, I doubt it matters in modern engines like the JA65 has)

 

[dmonkey]

A new bike shouldn't be doing that stock, I'd bring it back to the dealer. These don't even call for premium gas.

What you might be reading about is having an engine tuned for E0, and then running E10 without a closed loop fuel system. That would run leaner and could result in higher temps. Not an issue on this PGM-FI bike built for fuel with ethanol in it. In Thailand, where they're built, they run them on E20.

 

[m in sc]

well, it doesn't,. people just hate it for irrational reasons, usually emotional or political, not science based. But thats their choice... I have a garage FULL of vintage bikes (1967-up), some with tiny carbs & i run them a lot, and ethanol hasn't hurt a single one ever, even after some sit for a few mos..

This bike was designed to run on it, just like every. modern. car. I also seriously doubt you run hotter engine temps than i do, im in South Carolina and mine on 100+ degree days wringing its neck. its never pinged once, stock or not (its been both) You may be hearing something else. But since 2021, the only overheating issue i ever ran into was with a big bore kit and running it lean w too small an injector, and that was MY fault. Even then, it really didn't detonate. Air-cooled motors aren't inherently quiet. .02

 

[Dia1Up]

well, it doesn't,. people just hate it for irrational reasons, usually emotional or political, not science based. But thats their choice... I have a garage FULL of vintage bikes (1967-up), some with tiny carbs & i run them a lot, and ethanol hasn't hurt a single one ever, even after some sit for a few mos..

This bike was designed to run on it, just like every. modern. car. I also seriously doubt you run hotter engine temps than i do, im in South Carolina and mine on 100+ degree days wringing its neck. its never pinged once, stock or not (its been both) You may be hearing something else. But since 2021, the only overheating issue i ever ran into was with a big bore kit and running it lean w too small an injector, and that was MY fault. Even then, it really didn't detonate. Air-cooled motors aren't inherently quiet. .02

I think there's a difference between wringing it's neck at 40+ mph, vs wringing its neck at about 12 mph. I think that's where I'm having the most issues. 30C outside (or more), going up steep hills not breaking 25km/h in second gear. Lots of heat, little air flow. (We are talking hills are full throttle in 2nd, some I have to gear down to 1st)


So I guess sill ask again, is there an engine temp I should be looking for?

 

[m in sc]

honestly, not really. you're describing 2 different things. pinging is combustion chamber pre-detonation. oil temp is another thing. while the heat is created by the combustion (and mechanicalfriction), typically oil temp around 190-240f w conventional oil is good. the spark plug will show pred-detonation conditions but predetonation will typically hole a piston if its extreme.

these motors are designed to do exactly what you're describing you use it for..pushing a motorcycle atv40 mph wide open vs 12mph wide open .. heat is heat. . it takes very little airflow to cool an aicooled motor. thqts the beauty of them.

be aware. a cold motor can ping, and an overly hot motor doesn't always.

 

[DeadguyAle]

@Dia1Up
Air cooled motorcycle engines have been around since day one so the technology is pretty well sorted out and can take a lot of hard use without becoming problematic.
The "cooked" oil is most likely just normal oil from a wet clutch bike. The wet clutch sheds particulate matter that darkens the oil and can make it smell somewhat burnt.
Google is saying that air cooled motorcycle head temperature can run up to 375 degrees F with 270 F and above being on the high side. Get a laser temp reader and use it to track the head temperature, will help to identify if overheating is actually contributing to the issue.
Pinging or pre-detonation can be caused by carbon buildup, doubtful in a low mileage bike or possibly a small manufacturing defect in combustion chamber or timing issues.
Ongoing pinging pre-detonation problems would indicate a trip to the dealer might be in order before it becomes a major breakdown.

 

[Dia1Up]

@Dia1Up
Air cooled motorcycle engines have been around since day one so the technology is pretty well sorted out and can take a lot of hard use without becoming problematic.
The "cooked" oil is most likely just normal oil from a wet clutch bike. The wet clutch sheds particulate matter that darkens the oil and can make it smell somewhat burnt.
Google is saying that air cooled motorcycle head temperature can run up to 375 degrees F with 270 F and above being on the high side. Get a laser temp reader and use it to track the head temperature, will help to identify if overheating is actually contributing to the issue.
Pinging or pre-detonation can be caused by carbon buildup, doubtful in a low mileage bike or possibly a small manufacturing defect in combustion chamber or timing issues.
Ongoing pinging pre-detonation problems would indicate a trip to the dealer might be in order before it becomes a major breakdown.

Tytytyty


I do notice it's in mid throttle, I wonder if it's just leaning out a bit much. Sadly common with modern fuel mappings. I've decided that I'm going to ignore the spark knock tbh, it's 9 very laid back hp, and an engine that is known to be absolutely insanely reliable.

 

[They Call Me Jello]

What is a "Colder plug"? Never heard of this before

 

[Austin125]

Spark plug heat range…

One of many explanations

 

[They Call Me Jello]

Spark plug heat range…

One of many explanations

WOW and thank you for the explanation. Who 'da thunk it

 

[Dia1Up]

So far running in 7-15C weather, I've had 0 knocking at all. We will see once things heat up this summer. I still think I might see some issues once we get into the 25-35C+ range for sure

My town can hit 40c+ at very low humidity in the summer generally

 

[Dia1Up]

honestly, not really. you're describing 2 different things. pinging is combustion chamber pre-detonation. oil temp is another thing. while the heat is created by the combustion (and mechanicalfriction), typically oil temp around 190-240f w conventional oil is good. the spark plug will show pred-detonation conditions but predetonation will typically hole a piston if its extreme.

these motors are designed to do exactly what you're describing you use it for..pushing a motorcycle atv40 mph wide open vs 12mph wide open .. heat is heat. . it takes very little airflow to cool an aicooled motor. thqts the beauty of them.

be aware. a cold motor can ping, and an overly hot motor doesn't always.

I'm not describing 2 things differently at all I don't think


A big factor of pre-detonation/knock is temp. In an air cooled engine, oil is a very large part of temps over all.

I have a feeling it's more of a lean thing with mid throttle at low RPMs when the engine is hot, not enough fuel to cool cylinder temps. Dumping fuel into the cylinder can reduce knock, hence why I don't have issues at higher throttle or "wringing it's neck at 100+ degrees" (also why modern cars like direct injection)

On one hand I stand by what I said about not caring because this engine is indestructible, on the other, knock is bad heh. We will see how this year goes.

 

[m in sc]

detonation will blow a hole in a piston, break rings, destroy crank bearings, groove piston pins, etc. pinging is igniting mixture when the piston is still moving up. might as well hit the top of the piston with a hammer. Oil temp has nothing to do with that. However, High oil temp can be caused by a motor that detonates. they are absolutely 2 different things. I have motors that don't use engine oil. (2 stroke) and they can detonate w no other heat issues. air or liquid cooled.

 

[Dia1Up]

detonation will blow a hole in a piston, break rings, destroy crank bearings, groove piston pins, etc. pinging is igniting mixture when the piston is still moving up. might as well hit the top of the piston with a hammer. Oil temp has nothing to do with that. However, High oil temp can be caused by a motor that detonates. they are absolutely 2 different things. I have motors that don't use engine oil. (2 stroke) and they can detonate w no other heat issues. air or liquid cooled.

How does oil temp have nothing to do with that?

Hot oil, means hot motor in air cooled applications, some even call air cooled engines "oil cooled"

Regardless, my point of cooked oil, was the fact I had cooked oil, which probably means my engine was running too hot

Not all knock immediately detonates engines. If it did, cars wouldn't bother with knock sensors. Otherwise the engines would just blow at the first knock


So yeah, I think I had knock. Probably because my engine is too hot with lean fuel mapping at mid throttle. Makes me wonder if I should invest in some better head cooling