Compare and Contrast: The 650s

As you may know, the weather south of the border in Baja is getting to be just about 
perfect for riding. Naturally, Elden and Pauline couldn’t pass up an opportunity and are 
traveling to Mulege with several other riders. Someone, however, has to keep the place 
running, so I’m filling in on Technical Insights with a report on engine temperatures and a 
comparison between the KLR-650 and DR-650.

Elden and I have talked many times about the pros and cons of the DR-650 and KLR-650. 
The discussion often turns to engine cooling actual running temperatures. Earlier this 
summer while investigating a popular aftermarket computer set-up, I noticed the company 
was using a gasket-sensor to gather head temperature information for air-cooled bikes. I 
searched in vain to find a sensor/display combination at a reasonable price that could be 
used to check head and/or oil sump temperatures for the DR and KLR. By chance, I 
happened upon a potentially useful tool in a Harbor Freight catalog – a non-contact 
temperature sensor. Long story short, after listening to me talk about how this might make 
for a good test and article, but knowing my tendency to procrastinate, my lovely wife 
ordered one for me. When it arrived, I immediately tested it on everything in the kitchen 
(much to Mindy’s dismay…).  We were in business!

For those of you with a scientific mind, we came up with the following controls for our test. 
Both bikes were stock configuration with regard to the airbox, jetting, and exhaust. We 
removed both bash plates. Elden and I happen to be nearly the same size and weight, 
though etiquette prevents me from pointing out who is actually heavier… We took the 
readings in the same order at each stop, and we started and stopped the engines at the 
same time. We rode a meandering mountain road devoid of any sharp curves, allowing us 
to run exclusively in top gear. One thing we didn’t intentionally try to keep the same was 
RPM. This was intended to be a test of the two models under actual riding conditions. If 
one bike was geared higher or lower, so be it.  The DR-650 was geared with 14/42, 
equivalent to 15/45; and the KLR-650 was geared at 15/44. Note that stock for each bike 
would be 15/42 for the DR and 15/43 for the KLR. Surprisingly, we found that our RPM 
was the same when riding nose-to-tail at 4000 RPM and 4500 RPM. Since the DR was 
geared the equivalent of one tooth lower on the rear sprocket than the KLR, it reinforces 
the fact that 5th gear on the DR is higher. Another point worth remembering is that the DR 
was geared essentially three teeth lower than stock (the KLR one tooth lower than stock).

Our real intent was to see the relative differences between the two bikes under normal 
riding conditions, and also to note any trends that might reveal themselves. Although the 
temperature sensor is advertised as accurate to within 2%, the actual figures should not 
be relied upon for any reason.

We planned three stops measuring six different locations around the engine. The first 
stop was approximately 25 minutes and 15 miles out of town; enough time to get the 
engines fully warmed up and get out of the in-town traffic. This leg was fairly level, with the 
last 10 minutes or so on the highway. The second and third stops were approximately 10 
miles and 10 minutes apart, with riding conditions characterized by open road, 
predominately up-hill to the second stop, and down-hill to the third. We took engine 
temperatures at the following locations: 1. center of oil filter cover, 2. center of clutch 
cover, 3. center of dyno cover (actually just to the right to avoid the cap), 4. oil sump 
adjacent to oil drain plug, 5. center of cylinder wall, and 6. head adjacent to intake.

You can see the results obtained in the series of graphs (a table of actual
temperature readings is included at the bottom of the page).  The DR-650 ran hotter
at every point, particularly at the cylinder and head. Also, note that both bikes maintained
fairly stable temperatures throughout, a positive attribute for both cooling systems.
Also note that the downhill comparison showed a measurable reduction in cylinder,
and especially head, temperatures on the DR. 

Oil Filter Cover

Oil Filter Cover

OK, Deuce, but what does that tell me?”  First of all, don’t be surprised at the higher head
and cylinder temperatures of the DR. The KLR-650 has a water jacket to absorb and
dissipate heat through the cooling system. The DR cylinder is lined with nicosil which
speeds the transfer of heat from the combustion chamber to the outside. Air
convection and an efficient oil cooler also contribute to cooling. I would be more
concerned if the DR wasn’t hotter at the cylinder and head, because more of that heat
would be sinking into the rings and piston. Also, I would say that the oil cooler works quite
well as evidenced by the stable temperatures around the engine case and oil sump.
The decrease in temps for the DR on the downhill leg also lends credibility to its ability to shed heat.
It took advantage of the lower strain on the engine and managed to cool off measurably.
Clutch Cover

Clutch Cover

We took one reading at the header adjacent to the exhaust outlet which led to a couple of
interesting observations. The temperatures were 280 degrees for the DR and 250
degrees for the KLR; the KLR is actually creating a lot of heat internally even though
the cylinder and head temperatures don’t show it. Also, the small difference between
the exhaust temp and cylinder/head temps on the DR highlights its efficiency at transferring
heat outward.
Dyno Cover

Dyno Cover

Although only three stops, the temperatures were pretty stable on each bike and I don’t
think more stops would necessarily have revealed additional information. Remember,
the intent was to get an idea of where the bikes were running in relation to temperature,
and note the differences between them as well as any trends.

Oil Sump

Oil Sump

Lessons Learned. First, the DR runs hotter. In our experience though, we’ve never heard
of a DR overheating, and we’ve found they use much less oil than the KLR. I recently had
the opportunity to attend a Motorcycle Safety Foundation Experienced Riders Course.
Those of you who’ve taken one know that you spend a good part of the day either idling, or
in first or second gear at no more than 20 mph. This day was well over 80 degrees,
sunny, and in the open on a hot asphalt course. A rider on a Harley Davidson Road
King commented that his bike was cutting out due to the heat. The DR never missed a
beat, thanks to its hard working oil cooling system which includes an oil jet that
constantly sprays the underside of the piston dome with oil as well as  an oil feed coming
straight from the oil cooler to cool the top end. For DR riders, the hotter temperatures
should at least make you take pause before deciding to use a cheap motor oil (we
recommend Mobil 1 Synthetic, Golden Spectro, HP4M, or similar high quality oil), or
making any engine modifications that might increase temperatures even more.

Cylinder

Cylinder

For KLR riders, you can see how much work your water jacket does. Make sure you check,
and properly service as necessary, your coolant. Since the KLR is not designed to
pass heat in the same manner as the DR, you don’t want to handicap your cooling
capacity.

Finally, in stock configuration the DR is geared higher than the KLR, especially 5th
gear which seems more like an overdrive. Remember that the deciding factor on how
you gear your bike should be how you ride your bike. If you load it up with gear, ride tight
twisty roads, or even have a tall sitting height like me (lots of wind drag!), you probably
want to add a tooth or two to the rear sprocket. However, a smaller, lighter rider
who doesn’t put a lot of extra weight on the bike and rides open roads can probably pull 5th gear with stock gearing.

Head

Head

The KLR-650 engine seems to handle lugging better than the DR-650. The heavier KLR flywheel helps keep the crank moving and the one-spark combustion chamber acts like a “C average”high school student – it’ll do the minimum, but it’s more than happy to shove some of the work right out the exhaust ports. The DR gets less help from its lighter flywheel and combined with its over-achieving two-spark combustion chamber, gives the impression from the saddle that the engine is really hammering away at itself. The key is to listen to your engine. Don’t make it work too hard. If riding conditions are working against you and you can’t keep your revs up, drop back to 4th and give it a break. For you DR riders out there, I get the following RPM/MPH readings with 14/42: 4000/60, 4500/68, 5000/76.

  DR-650
KLR-650
DR-650
KLR-650
DR-650
KLR-650
Oil Filter Cover
196
178
201
180
187
178
Clutch Cover
175
157
180
159
170
160
Dyno Cover
201
176
205
180
197
176
Oil Sump
215
178
217
177
213
183
Cylinder
258
195
264
210
259
210
Head
265
182
260
189
244
181
1st Reading
Level
2nd Reading
Uphill
3rd Reading
Downhill
* All temperatures are degrees Fahrenheit

 We’ll run more comparisons in the future and we’ll keep you posted. If there’s something
you’ve always wanted to know, drop us a line. In the meantime, check your six and ride
safely!