[Leofric]

As it says the 350J engine is oil/air cooled why doesn't it have an oil cooler ?

[Olsonson]

I guess it's not necessary with 20bhp.
The oil cools certain area's in the cylinder head. The manual has schemas on the oil flow.

Anyway, it would be nice to keep an eye on the oil temperature in hot conditions and long trips. But maybe it's just the ex Beetle owner with some traumatic experience in me.

[ptclassic]

There is probably some kind of labirint for the oil travel on the head to cool down..

It's not good for this bikes to stay on idle for long time after a long trip. I noticed that on traffic it gets hot

[hotrob]

As it says the 350J engine is oil/air cooled why doesn't it have an oil cooler ?

I too have always thought of an oil cooled engine as having an oil cooler, but in this engine's case what Royal Enfield mean is that oil is directed around the spark plug area and the exhaust valve, to cool those hotspot areas.  The oil then loses heat by the normal air cooled method.  So for me, I just consider it an air cooled engine, just the same as an air cooled engine that squirts oil under the piston crown to cool the piston would not normally be called an oil cooled engine.

A water cooled engine with an oil cooler is normally just called a water cooled engine, so the 350J engine without an oil cooler should surely just be called an air cooled engine?  The engine is only air cooled; the oil is used to help distribute the heat more evenly around the engine.

[longstrokeclassic]

It’s just a marketing waffle. All engines that circulate oil are cooled by their oil to some degree.
 

[Crabsapper]

To be fair, at least this does have a specific cooling circuit with part of the oil flow doing nothing but cooling.

As regards heat levels, the bike was designed from the outset to cope  with Indian temperatures. I hardly think the designers haven't taken into account a 45°c traffic jam in Mumbai.

It's funny how people anthropomorphise engines with regards to heat. In many cases the engine is hotter when YOU can't feel it.

[ptclassic]

To be fair, at least this does have a specific cooling circuit with part of the oil flow doing nothing but cooling.

As regards heat levels, the bike was designed from the outset to cope  with Indian temperatures. I hardly think the designers haven't taken into account a 45°c traffic jam in Mumbai.

It's funny how people anthropomorphise engines with regards to heat. In many cases the engine is hotter when YOU can't feel it.

Yes, very funny 

[ButteMT]

All engines are cooled by air and oil.  Some add liquid cooling with a radiator.
Given how many bikes and miles RE have tested their hardware, I'd think that they would have a pretty good grip on cooling...
I lasted this summer on mine in LA where the temps got to 110ºf+
No issues.  Just keep your oil full and clean.  That's how you keep it running...

Ride Safe 🙏🏼

[olhogrider]

Marketing. When they added an oil cooler to the 650 people liked the idea so now they say air/oil as if that's different from air cooled. It isn't. It's the same way BMW says their turbocharger is twin scroll or some such nonsense because a twin turbo sounds better even though it only has one turbo with two outlets. 

[Curious wanderer]

As it says the 350J engine is oil/air cooled why doesn't it have an oil cooler ?

Is has, it’s all that finning around the cylinder head, it serves to cool the oil with airflow and do a bit of air cooling as well. Dual use and good engineering.

It doesn’t need an oil cooler, which most of the time only serves to overcool the oil in our northern climes unless you add the complexity of thermostats and bypasses.

Helps when you’re running at constant high power in racing, for our bikes, not needed. My oil temp gauge shows it doesn’t get that hot anyhoo.

[3oro]

Driving the motorcycle in June at the official 47C, I did not notice that it overheated. Except me

[Leofric]

Is has, it’s all that finning around the cylinder head, it serves to cool the oil with airflow and do a bit of air cooling as well. Dual use and good engineering.

It doesn’t need an oil cooler, which most of the time only serves to overcool the oil in our northern climes unless you add the complexity of thermostats and bypasses.

Helps when you’re running at constant high power in racing, for our bikes, not needed. My oil temp gauge shows it doesn’t get that hot anyhoo.

Cooled by the fins on the cylinder head - so air cooled then ! 

[20MarkIII]

There's a thread somewhere that shows the complete oil circulation on a BMW engine that uses the same oil cooled concept as the J platform. I do think that good quality full synthetic oil is the way to go to help keep the 350 from overheating. My experience anyway. I'm using Motul 300v 15w-50 and will continue with it.

[Curious wanderer]

Cooled by the fins on the cylinder head - so air cooled then ! 

Yes, but ultimately, isn’t every engine air cooled😂😂😂?

[Leofric]

Yes, but ultimately, isn’t every engine air cooled😂😂😂?

Far be it from me to want to labour the point but,generally I think of engines as :_
Water cooled (with radiator ,fan ,coolant, engine fins not strictly necessary .
Oil cooled, with engine fins and external oil cooler grille.
Air cooled, with engine fins.