Oil Sight Glass?

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pdee4t

hey guys.
how accurate is the sight glass? i fixed an oil leak by replacing the copper washer on the drain plug.
i did a complete drain and full top up but noticed that the oil level in the sight glass remains the exact same when hot or cold.

i topped up with 1.25 litres of oil as stated in the manual. i measured it.
i put the motorcycle on a horizontal motorcycle stand, and ran the bike. when i checked it while the motor was cold, the oil level was about 3/4 of the way up, then i ran the bike until the cooling fan came on, re-checked the oil level in the sight glass and it was about half way. then i let the bike cool down, to go wash it, re-checked the oil level in the sight glass and it was still half way(on a cold motor).
bike was on the stand the whole time.
just wondering if anyone would know why? or if its normal or not?
doesn't make much sense to me.

the bike is a KTM 450 EXC 2004 model.
 
PALMER84ONE

PALMER84ONE

Little oil hangs up in the head. What I do when I change oil on my bikes (all different than yours) is once the drain plug is out, lay it over for a few seconds, strait back up, lean to other side. This insures all oil is down and over any bulkheads inside. I always check site glass on level ground, not the stand. I out in the recommended amount and run it, never really worried if the site glass was correct. There are two marks on mine, hi and low.
 
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pdee4t

yeah in the manual it says that the oil level should be 1/4 of the way up when cold(bottom edge of sight glass) and 3/4 of the way up when hot(top edge of sight glass).
just wondering why the oil level stays the same hot and cold? doesn't make sense. shouldn't it expand/thicken?
 
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ossagp

Thicken when it is warm? Curious as to why KTM made that statement about the level being higher warm. If I didnt have reason to know better I would think they were talking about coolant!!I have rigs that take 12 gallons and with the engine shutoff I get the same readings hot or cold as long as I let the oil have a few minutes to drain back down in to the pan. Some of the honda xr's will read high when cold because the oil cooler drains down and gives the sump a false high reading when it has been sitting for a length of time.
 
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rezrider

rezrider

ossagp:
Thicken when it is warm? Curious as to why KTM made that statement about the level being higher warm. If I didnt have reason to know better I would think they were talking about coolant!!I have rigs that take 12 gallons and with the engine shutoff I get the same readings hot or cold as long as I let the oil have a few minutes to drain back down in to the pan. Some of the honda xr's will read high when cold because the oil cooler drains down and gives the sump a false high reading when it has been sitting for a length of time.
Click to expand...

Your thought makes sense (as do most of your posts....) I know way back when I had my TT when cold it was at 1/2, when warm it was higher... maybe due to settling when sitting??? :noidea:
 
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ossagp

Liquids settle? On the tt it has to do with the reservoir draining down after it sits a little if you are talking about a tt 500. The ktm may be a similar situation, but darn I thought I understood the schematic that I saw. (Falls under the reason to know better).
 
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PawPaw

There are several bike makers that say the same thing about the sight glass. I know KTM, Husqvarna, Ducati and a few others do state that the oil level will be higher when hot. I have a Husqvarna and I have hot seen this happen, but the manual sure tells me it will. I don't understand the logic either.

Paw Paw
 
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ossagp

I shouldn't even be talking about that this week. I am fixated on xr 250's. Can't remember from them and 600's as to which is high when. For some reason I am remembering rfs engines as case fillers. They have something I am missing.

I was really more perplexed with the " thicken" term.
 
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Mihylo33

Mihylo33

When heated individual molecules grow more dense, Hens the translation of thicken. The oil itself expands even though it feels thinner it is thicker. Hot oil pours easier because the molecules themselves are in a heated and agitated state. Kind of like when the wife spends your morning telling you what she wants done around the house, you grow agitated and just want to get out the door....
 
SRAD97750

SRAD97750

Moderator
Staff member
The oil's molecular structure is expanding due to heat, but since an engine doesn't get anywhere near the boiling point of oil, IMHO, the rise in volume will be extremely minimal.

I think the 'Viscosity Improvers' and 'pour point depressant' additives in multi-viscosity oil are changing the Viscosity of the oil and manipulating how the oil moves through the engine, giving different readings (on a dipstick or sight glass) as the temperature changes. Examples: Surface tension making the oil 'climb' the walls.

EDIT: Another thing I thought of as the engine heats up it expands as well. Could this possible cause the oil level to rise as the volume of storage decreases?
-BIG DAN:thumb:
 
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ossagp

Mihylo33:
When heated individual molecules grow more dense, Hens the translation of thicken. The oil itself expands even though it feels thinner it is thicker. Hot oil pours easier because the molecules themselves are in a heated and agitated state. Kind of like when the wife spends your morning telling you what she wants done around the house, you grow agitated and just want to get out the door....
Click to expand...


Molecules and atoms typically expand when they get hotter, they end up with more space (not less) withing themselves. So the density ends up dropping. Air molecules get denser when it gets warmer? They don't do they? Some compounds like water grow again when the temperature drops to the point of crystalization. Ice is lighter than water for that reason, and floats on it's mother substance.

Oil isn't thicker as it get hotter. Oil won"t gain the volume mentioned other than gases expanding within them, something modern oils do scant little of and less yet after being heated a few times to evaporating off any thing that boils at a low temp. In the case of multiple viscosity oils like a 15-40, they have an additive package that lets the pour like a 15 weight oil at a cold temp, and don't THIN out any further than the stated 40 straight weight would at higher temperatures.

If heat expansion was the reason for what is a pretty drastic change in volume I think anyone would have noticed it in the other applications. I think I am just missing something about what holds the oil in the sight glass area on the RFS engine.
 
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