Fan cut in Temp

ballisticexchris · Dec 4, 2019

WJBertrand said:
Huh? The coolant is cooling the cylinders and cylinder heads, it does not directly cool the clutch, am I missing something? Also, clutch friction (when slipped) can generate temperatures well above coolant temps. I don't think there are any internal combustion engines designed to operate at 300F.

I guess time will tell. I’m just going off what I have experienced over the years of running every one of my bikes well north of 300 deg regularly when rock crawling. My air cooled XR 600 topped out over 330 degrees. Ironically it was the only bike that ever left me stranded. Engine locked up from an oil related failure (frame drain plug fell out).

I have run temperature strips on my clutch and a coolant gauge. When going super slow for long periods the numbers end up matching. For short bursts of clutch abuse then yes the clutch pack only gets hotter.

The good news is I got rid of my 300 and no longer doing super long stupid trails anymore. I’ve decided to keep running Evans in my Beta and OEM Yamaha coolant in my Super Tenere.

steve68steve · Dec 4, 2019

WJBertrand said:
Huh? The coolant is cooling the cylinders and cylinder heads, it does not directly cool the clutch, am I missing something? Also, clutch friction (when slipped) can generate temperatures well above coolant temps. I don't think there are any internal combustion engines designed to operate at 300F.

Get outta my head!

Friction plates bathed in oil as an indicator of engine temp?

Metal parts with tightly toleranced clearances between them running 100 degrees F over design spec?

ballisticexchris · Dec 4, 2019

steve68steve said:
Get outta my head!

Friction plates bathed in oil as an indicator of engine temp?

Metal parts with tightly toleranced clearances between them running 100 degrees F over design spec?

Yes sir! That is 100% correct. No science or overthinking involved. Just hit the trail and ride. At a certain point the whole engine runs at at almost temperature. Riding a 9 mile trail at walking pace will show you this. This is why it's very important to run really good Ester based oil. Running an engine at 100deg over spec is not going to hurt a thing anything major other than clutch parts. I have proven this time and time again. The reason the clutch parts are hurt is from all the slippage/friction.

steve68steve · Dec 5, 2019

ballisticexchris said:
.... No science or thinking involved.

Finally, something we can agree on.

Checkswrecks · Dec 5, 2019

Chris -
Design tolerances are based on a set of inputs and one biggie is operating temperature. For example, there is a completely different set of assumptions and way to design air cooled vs liquid cooled engines. Liquid cooled engines are designed to much tighter clearances AT OPERATING TEMP.

I appreciate that you've got strong opinions because you run your machines 100F over what the designers called for and keep making it home. They are your bikes and your choice, so viva la difference. However, I and apparently some others just don't agree and probably won't be going down that path.

fwiw - Coolant only carries away roughly (depends on machine) half (or less) of the engine heat, primarily from around the piston bores and heads. The cutaway below shows the coolant passages in green. Oil carries away most of the heat from the crank, and almost all from the clutch and transmission. The cooling of your clutch plates has little to do with coolant temp.

ballisticexchris · Dec 5, 2019

Well once you start rolling through miles of rocks the whole darn engine gets hot. And I do know that at least the clutch cover temps and coolant temps end up pretty much the same temperature. And then the gas stars to boil. I don't have any fancy cutaways of another engine. Just my eyes on my motors when riding and torn down for service. I'm a believer in using the best oil and coolant possible for my riding conditions.

And you may not agree with me but there are times you will not have a choice. When that trail turns into a nasty downhill rocky mess for 5 miles and the only way out is back up the mess or continue, well you get the idea. The bike is going to get hot.

Thankfully I'm pretty much done with that kind of riding.

MattR · Dec 5, 2019

A coolant that allows the motor to run at 100f above its design temp is not a good coolant.

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steve68steve · Dec 5, 2019

Checkswrecks said:
Chris -
Design tolerances are based on a set of inputs and one biggie is operating temperature. For example, there is a completely different set of assumptions and way to design air cooled vs liquid cooled engines. Liquid cooled engines are designed to much tighter clearances AT OPERATING TEMP.

I appreciate that you've got strong opinions because you run your machines 100F over what the designers called for and keep making it home. They are your bikes and your choice, so viva la difference. However, I and apparently some others just don't agree and probably won't be going down that path.

fwiw - Coolant only carries away roughly (depends on machine) half (or less) of the engine heat, primarily from around the piston bores and heads. The cutaway below shows the coolant passages in green. Oil carries away most of the heat from the crank, and almost all from the clutch and transmission. The cooling of your clutch plates has little to do with coolant temp.

Seeing the pic reminded of another biggie:

Linear thermal expansion is a percentage - meaning, the longer something is, the more length it pics up. 10% of an inch is a lot less than 10% of a mile.

The valves are something on the order of 4 - 6 inches long. The valves are what close to create compression, and open to admit air/ fuel and release exhaust gases. The amount that they open is a critical maintenance issue, governed in part by the gap between the bucket and the cam lobe for each valve. This gap is something like .12 - .15mm. That's .0047"- .0059" (someone jump in and correct me if I got the spec wrong - manual is out in the garage).

100 deg F change on a 6" piece of steel is 6" x 100deg x .0000072in/in/ F, which is .004". (again, someone check my math).

.004"

If the valve is 6" long, you are losing ALL of your valve clearance because of the thermal expansion caused by that additional heat. ALL of it.

So, great, you're crawling your hot bike along those rocks like a super hero, and the bike continues to run.
And your valves are floating, which is robbing power, and contaminating your oil, and shortening the life of your engine, and maybe annealing parts, and maybe melting valve seals, and, and, and....

I ate fish the other day. Fish contains mercury. I didn't die. Therefor, mercury is perfectly safe and swallowing it has no ill effects.

ballisticexchris · Dec 5, 2019

MattR said:
A coolant that allows the motor to run at 100f above its design temp is not a good coolant.

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You said it. That’s why I use the Evans. Normal 50/50 mixed coolant will boil out and the engine will be cooked.

Jlq1969 · Dec 5, 2019

Checkswrecks said:
Chris -
Design tolerances are based on a set of inputs and one biggie is operating temperature. For example, there is a completely different set of assumptions and way to design air cooled vs liquid cooled engines. Liquid cooled engines are designed to much tighter clearances AT OPERATING TEMP.

I appreciate that you've got strong opinions because you run your machines 100F over what the designers called for and keep making it home. They are your bikes and your choice, so viva la difference. However, I and apparently some others just don't agree and probably won't be going down that path.

fwiw - Coolant only carries away roughly (depends on machine) half (or less) of the engine heat, primarily from around the piston bores and heads. The cutaway below shows the coolant passages in green. Oil carries away most of the heat from the crank, and almost all from the clutch and transmission. The cooling of your clutch plates has little to do with coolant temp.

If you have more pics of these, or other angles, upload them to the forum. I want to find some defect

ballisticexchris · Dec 5, 2019

Jlq1969 said:
If you have more pics of these, or other angles, upload them to the forum. I want to find some defect

Better yet I would like to see the Super Tenere forum engineers actually ride and suffer like I have. Some of The trails I’ve ridden have had me puking and praying I would make it back to my truck.

Checkswrecks · Dec 5, 2019

Chill - It's OK for people to have different opinions. For example, I've never seen an oil/religion/political thread change somebody's mind about what is best for their conditions. AND THAT'S OK!

As for experience - ummm - trust me in that we have some REALLY experienced people around here who can humble the vast majority of us. And those guys are usually the humble ones. There are some really good engineers (including factory) and if you want to focus on crawling desert rocks I can think of a couple guys with scary numbers of years doing that who make it look natural. Heck, we have guys in their 70s who are still motocrossing. Every time I think I've met somebody amazing around here, somebody else amazes me more.

Checkswrecks · Dec 5, 2019

steve68steve said:
Seeing the pic reminded of another biggie:
If the valve is 6" long, you are losing ALL of your valve clearance because of the thermal expansion caused by that additional heat.

Steve - Going to accept your numbers but we are on the same thought.

ballisticexchris · Dec 5, 2019

The guys who make rock crawling look natural don’t overheat motors like crappy novices such as myself. LOL!!!

gv550 · Dec 6, 2019

steve68steve said:
Seeing the pic reminded of another biggie:

Linear thermal expansion is a percentage - meaning, the longer something is, the more length it pics up. 10% of an inch is a lot less than 10% of a mile.

The valves are something on the order of 4 - 6 inches long. The valves are what close to create compression, and open to admit air/ fuel and release exhaust gases. The amount that they open is a critical maintenance issue, governed in part by the gap between the bucket and the cam lobe for each valve. This gap is something like .12 - .15mm. That's .0047"- .0059" (someone jump in and correct me if I got the spec wrong - manual is out in the garage).

100 deg F change on a 6" piece of steel is 6" x 100deg x .0000072in/in/ F, which is .004". (again, someone check my math).

.004"

If the valve is 6" long, you are losing ALL of your valve clearance because of the thermal expansion caused by that additional heat. ALL of it.

So, great, you're crawling your hot bike along those rocks like a super hero, and the bike continues to run.
And your valves are floating, which is robbing power, and contaminating your oil, and shortening the life of your engine, and maybe annealing parts, and maybe melting valve seals, and, and, and....

I ate fish the other day. Fish contains mercury. I didn't die. Therefor, mercury is perfectly safe and swallowing it has no ill effects.

The valve will certainly become longer due to thermal expansion, but also consider it is mounted in an aluminum head, and aluminium expands 2-3 times the amount of steel. Valve clearance may actually increase with temperature if both materials are subject to the same temperature increase.

Checkswrecks · Dec 6, 2019

gv550 said:
The valve will certainly become longer due to thermal expansion, but also consider it is mounted in an aluminum head, and aluminium expands 2-3 times the amount of steel. Valve clearance may actually increase with temperature if both materials are subject to the same temperature increase.

While you are generally right, exhaust valves lengthen more because they are in the direct impingement of the exhaust gas flow. The relative amounts are what decides how much is too much and the critical engineering temp data that only the factory head designer will have will include things like:
specific temps the valves will see,
valve stretch,
block dimensional changes,
piston gaps,
etc

steve68steve · Dec 7, 2019

gv550 said:
The valve will certainly become longer due to thermal expansion, but also consider it is mounted in an aluminum head, and aluminium expands 2-3 times the amount of steel. Valve clearance may actually increase with temperature if both materials are subject to the same temperature increase.

So if the head getting bigger drags the camshaft away from the bucket by a factor of 2 - 3 times the valve lengthening, we're back in the same territory of the entire spec being used up by thermal expansion, just in the other direction: valve gets .004 longer, head moves it .008 away. It's still a net change of .004 in position. Remember, our bikes have an interference engine: the valves have to be closed all the way for the piston to not hit them at TDC. I don't know how much the cam lift is, but that number is also getting bigger as it gets hotter.

There's the volumetric expansion, too: the camshaft is getting bigger and the journals it rides in are getting smaller. That reduces the oil film thickness and increases friction, which creates more heat and wear.

My suspicion is that the bucket-cam lobe clearance gap that we have to so carefully maintain is engineered for the exact purpose of dealing with the difference between a ~70deg engine torn apart for the inspection and a ~ 200deg engine running.

...like the SR-71 fuel tanks, which leak on the runway on purpose because thermal expansion at Mach whatever will expand and close the gaps. If the tanks were tight on the ground, they'd crumble during flight.

MattR · Dec 7, 2019

But some racing engines are built seized and have to be warmed up before they can be started. Which suggests that as the engine warms the tolerances get bigger not smaller.

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Cycledude · Dec 7, 2019

Interesting, I never heard that before but when it comes to racing the game really changes.

MattR said:
But some racing engines are built seized and have to be warmed up before they can be started. Which suggests that as the engine warms the tolerances get bigger not smaller.

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MattR · Dec 7, 2019

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Fan cut in Temp

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