Xr600 & xr650l aussie owners

Is this mod applicable to Xrs?

Yeah valid concerns.

I hate mud and avoid it as much as possible, I don't think it's too much of an issue in any case - the screen in front of the cooler should keep most of it away.

The oil cooler does feel a bit vulnerable to me. It's designed for the XR650L which has a slightly thicker left engine side cover, so it sits a bit proud of the engine cover. There's long spacers that mount the side plate of the cooler into the engine case and a good hit could cause some very unpleasant damage.

When I had a bash guard it did a reasonable job at protecting the lower part of the assembly but the upper couple of bolts were still a bit vulnerable.

Sadly I sold the bloody bash guard in the period between when the bike got stolen and when I got it back...

If this was true air flow wouldn't matter. It's the air molecules taking away the heat by CONTACT with the fins that has the biggest cooling effect, not by the fins radiating heat into them.

Theoretically and impractically, if the engine was in a vacuum and solely dependent on radiation for cooling it would overheat big time.

Another way to think about it is the opposite situation: the engine being submerged in water. The cooling would be extreme because of the contact with the water, not the radiation into the water.

And in relation to wrapped pipes, they'd have to be the dopiest trend ever. Apart from looking terrible and being hard to clean, they overheat the steel until it crystallises and shatters. Of course, preventing the steel being in contact with the air flow also reduces the total cooling of the engine.

Years ago after crossing the Simpson Desert in a Daihatsu Feroza my exhaust pipe shattered and lost a few inches behind a little rock guard where the pipe came down from the manifold and bent to parallel the floor.

The exhaust specialist who repaired it strongly recommended against having anything in that position blocking the air flow on the pipe as the problem would only recur in extreme conditions of high throttle and low speed such as climbing hundreds of sand dunes in low range.

It is absolutely true. The physics is very clear, and very simple. Read the bit I wrote about convection again, or just look up the physics of heat transfer.

From Hemings


Air-cooled engines have fins cast into their cylinders and cylinder heads that give the engine greater surface area through which cool air can pass.


So bigger fins means bigger (relative) surface area which means better cooling?

Perhaps the "radiator" misnaming has misled you: it is actually a heat exchanger and very little of its cooling effect is achieved from radiation of photons.

I think we're all in furious agreement on that at least.

No, the radiator is very aptly named. Go and look up the physics of heat transfer. Photons are not involved. This is basic physics.

If you really believe that I'm afraid I can't assist you further.

But I'll give it one more shot.

Photons are the ONLY way radiant heat travels. Radiated heat, whether from a black surface or an incandescent one, is a form of electromagetic radiation that travels in waves of photons.

That is why the heat from the sun can travel through the vacuum of space to warm the earth. There are no atoms or molecules to transfer the heat by conduction/diffusion, convection, advection or adsorption.

My mistake - I thought there was a different type of EMR at play.

Nevertheless, the basic physics remains - heat is radiated from the cylinder head fins into the surrounding air, where it it is carried away by convection.

There is no significant conduction of heat into air. Air is a terrible conductor of heat (which is why it's en effective insulator).

No doubt Mr Summers was having similar misgivings at the time

Mr. Summers was indeed concerned about engine cooling.
So much so that he recommended an oil cooler and having the exhaust header wrapped, but was against a bashplate that traps the heat.

https://4strokes.com/viewtopic.php?t=61

Things are pointing to something odd in your lubrication system, greyrider1. I've been checking the oil level in both my XR600s after sustained high rev running and the level has remained consistently high.

Also, the dipstick temperature gauge has been very consistent, suggesting it is staying in the oil.

With the gauge and remote temperature gun I got the following readings today - first column slow single track mostly first gear and second column when I arrived home after highway revs.

Air 23 24
Gauge 94 104
Head 112 140
Exhaust 235 385
Clutch cover 87 105
Frame oil tank top 68 88
" " " bottom 82 109

I'm very happy with these figures, which are at least as good as those for my RnineT Racer with its large oil cooler. So I won't be fitting a cooler to the XRs.

Birds are singing, sun is shining, just go for a ride

On oil system issues the big one with the XR600R is the screen in the bottom of the in frame oil tank.
With age and use the teflon layer on the cam chain guides wears through and then it wears the nylon base layer.
The worn nylon particles then travel through the oil system and clog the metal screen in the oil tank base fitting and restricting oil flow.

Those temps look pretty good ron50.

There might well be a difference in the construction of the frame between the xr's and xrl's. When I first got the xrl (16k on the clock and bone stock) it showed that behavior where the temp on the dipstick would drop whilst riding then jump back up to where I thought it should be when pulled up at the lights.

I always thought that the level fluctuates and after installing a sight tube I could actually watch the level change with changing rpm. No big deal but that lead me to investigate the oil system a bit more and over the years I must have read most if not all oil threads the are. It's probably safe to say that more xr,xrl,nx's have died from oil starvation to the top end than any other causes.

Atm i'm trying to get a little video sorted that shows oil pressure from a cold start to normal running temps
..gotta learn how to edit videos first.

It's even safer GR1 to say that the top end failures are caused by people not adhering to the 1000 km oil change intervals, using incorrect oils and ignoring excessive heat due to conditions.

In my 35 years of XR ownership, racing, spanner work and tour fleet responsibility consisting of about 80 different bikes in approx 220,000 collective km, not one of them has ever worn a top end or blown up. These things got flogged mercilessly, especially the tour bikes. The only bikes I've had to leave behind (dead) in 38 odd Cape York trips / Simpson crossings have been either DRs, DRZs, WRs, KTMs, or in rare cases, XRs that the owner has prepped himself and bought his own bike along. Stick to the basic rules, don't mess around with it because you're bored / curious, don't labour it to death (common) and problems simply don't occur. My 1990 survivor XR600 has never missed a beat. Engine has never been touched and not likely to in my lifetime.

I understand peoples' compulsive desires to learn / tweak / modify / believe everything online, but will always call bullshit when it needs called. I would say exactly the same thing in person if sitting in a bar chatting face to face to anyone about it.

Pic from Loyalty Beach 2002

I've got absolutely no reason to doubt what you're saying and with that track record I salute you.

But, can I humbly point out, you recommend oil changes every 1000km instead of Honda recommended 3000km. Why the lack of faith in what Honda says, and doesn't that constitute a modification already? ...just saying.

You aren't looking at the XL600 schedule are you GR1?

My 1992 handbook says every 30 operating days, 100 miles (yes 100, not 1000) 1600ks and more often for "severe use" or ridden in unusually wet or dusty areas.

I used to count the hours of use but these days just go by the colour of the oil: once it darkens I change it. Never touched the internals of the 92, 96 or 98 except for checking valve clearances.

Manufacturers will extend service intervals to make a vehicle more attractive to buyers. At the end of the day if the motors fails it will be well out of warranty and of little consequence to the manufacturer.

And GSXR is dead on the money. I read a story once about a mechanic that had won (But was disqualified) the Cannonball run in the US on a Harley. He was prepping the bike for a second run when they interviewed him. They questioned his choice of bike given its reputation for unreliability. His reply was “Harley’s are 100% reliable. It’s the people who work on them that make them unreliable.”