How slow of a speed for an air-cooled engine?

I've got a DR650 with an air-cooled engine. I know that continuous idling can overheat the engine. I'll probably do average speeds of less than 12 mph on dirt because I'll be going dual-up with my wife most of the time and do not want to spill this bike with her on the back. I anticipate that we are going to spill at some times and want to keep the speed low to lessen the impact. Even on logging roads and hard packed gravel roads around here you will find mud and soft dirt and sand. I already know what a DR650 with stock tires will do in this terrain. Going slow allows time to assess these conditions in advance and find a way to steer around them in many cases. In addition, we want to enjoy the scenery. No hurry to get anywhere. How slow can an air-cooled engine go before overheating kicks in and what detrimental effect does overheating have on an air-cooled engine? I do realize that ambient air temperature will affect heating but lets assume a worse case air temperature of 70 degrees F for this scenario.

Lows speeds with two, or even one up, will tax your engine, especially in hot temperatures with only light winds.

 

This would be one of the few times I would recommend a synthetic oil over conventional oils.

 

You can safeguard the engine by using an ester based synthetic oil such as Redline or Amsoil, using the correct grade of course. Esters

have a very high resistance to heat degradation (oxidation) and will provide much better protection to the ring area.

 

Keep a very close eye on the oil level in these situations.

 

You should also plan on changing the oil at intervals not to exceed 800-1,000 miles. The heat takes it toll, even on synthetics.

 The filter can be changed less frequently. 

 

In short, you can run the bike under these conditions, but serious considerations to engine oil are vital to preserving the life of your bike's engine.

Lows speeds with two, or even one up, will tax your engine, especially in hot temperatures with only light winds.

 

This would be one of the few times I would recommend a synthetic oil over conventional oils.

 

You can safeguard the engine by using an ester based synthetic oil such as Redline or Amsoil, using the correct grade of course. Esters

have a very high resistance to heat degradation (oxidation) and will provide much better protection to the ring area.

 

Keep a very close eye on the oil level in these situations.

 

You should also plan on changing the oil at intervals not to exceed 800-1,000 miles. The heat takes it toll, even on synthetics.

 The filter can be changed less frequently. 

 

In short, you can run the bike under these conditions, but serious considerations to engine oil are vital to preserving the life of your bike's engine.

 

Thanks for the information. 39 years ago when I was into bikes I wouldn't have to ask questions like this. But 39 years not on a bike I've got a lot of catching up to do. I wouldn't be able to pass the NY state motorcycle test now if I had to take it. I got my NY state motorcycle license 43 years ago and kept it active all these years even though I thought I would never be back on a bike again. Gives a whole new meaning to never say never.

On the flip side, the big DR is actually pretty hard to overheat. Some of the big air cooled bikes have overheating issues, but very very rare with the DR.

On the flip side, the big DR is actually pretty hard to overheat. Some of the big air cooled bikes have overheating issues, but very very rare with the DR.

Thanks for the information. Could you tell me how you heard about it and is there a technical explanation for it? Trying to learn everything I can about the DR650, both from published sources and personal experience.

Thanks for the information. Could you tell me how you heard about it and is there a technical explanation for it? Trying to learn everything I can about the DR650, both from published sources and personal experience.

I had one for a while and did a lot of research. Some of the guys that go crazy with mods and dyno runs actually said they had to turn the cooling fans off at the dyno because the bike wasn't getting up to ideal temperature. The air cooling is well designed, and the oil cooler is large and well placed. They work together to more than adequately cool the relatively low-tech engine. There are some serious big bore kits out there, and from what I recall nobody had any issues with cooling, even getting up close to 800cc's.

Google for DR650 forums- there are some good resources for the bike out there.

I had one for a while and did a lot of research. Some of the guys that go crazy with mods and dyno runs actually said they had to turn the cooling fans off at the dyno because the bike wasn't getting up to ideal temperature. The air cooling is well designed, and the oil cooler is large and well placed. They work together to more than adequately cool the relatively low-tech engine. There are some serious big bore kits out there, and from what I recall nobody had any issues with cooling, even getting up close to 800cc's.

Google for DR650 forums- there are some good resources for the bike out there.

Thanks for the information.

I ride my Elliptigo typically between 10-14 mph and you'd be surprised what a nice breeze you create when moving that fast.  Point being, you'd be surprised how much cooling effect the moving air has, even at 10 mph.  We've putted around all day long climbing hills and running trails and never going very fast. In fact that's pretty much the definition of my and many others off road riding.  lOL

  Never any heat related issues. If it does get really hot it will ping, if it pings you pull over and get off and let it cool down or get to a road where you can up the speed for a bit till it cools down.

 10 mph on a big, under stressed, torque monster like that is barely off idle, yet lots of moving air versus actually idling while motionless.  

No worries.  

Edited by MindBlower

You'e not going to hurt it. At lower speeds, this engine isn't working hard enough to really "overheat."

 The big DR is air/oil-cooled, not air-cooled. It has a big oil cooler, an oiljet that sprays the piston, extra oil passages in the engine, and enough cooling fins to run just fine with the oil cooler bypassed.

 

 As described before, the Suzuki Advanced Cooling System (SACS) works extremely well. The big DR has even fewer reported cases of overheating than the vast majority of liquid-cooled bikes. As long as you have adequate oil and good oil flow, the DR isn't known for overheating, even with the oil cooler bypassed and running desert sand, unless something else is already wrong with the engine.

 

 I've had my DR idling on the side of a road for over an hour on a hot summer night, to provide light to a rider with bike problems. There wasn't even a hint of pinging or other issues. When I got back on the road, the DR pulled out without a whimper. I abuse my DR in the FL heat and sugarsand. It hasn't even pinged once. Idling along, without towing a fat guy on a 700cc utitlity quad with 4 flat tires, isn't likely to overheat a healthy DR with good oil in it. The bike sheds heat extremely well.

Edited by Kommando

Thanks for the inputs. Glad to hear the DR650 has a good cooling design.

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