Riddle Me This Thumper Dudes.....

Chili

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#1
My son just bought a new 07 RM-Z 250 so being the ham fisted hack mechanic that I am I decide I'll actually look at the manual prior to changing the oil (apparently 1 hole for exit, one for entry is too easy for you 4 stroke guys :laugh: ) Anyway I digress, onto my question. Why on earth does the manual ask me to remove the TDC plug for an oil change? I'll assume some Japanese engineer has a good reason but I can't think of it so far.
 

Rich Rohrich

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#2
Doug - Think about the oil flow in a dry sump oiling system (or look at the diagram in the manual for a visual aid) versus a wet sump system like your truck uses and I think it will make more sense. ;)
 

Chili

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#3
The only logic I can come up with is it helps vent the system and allows the oil to drain completely, same as trying to drain the coolant when you leave the rad cap on? Do I get a pointy hat or am I on the right track?
 
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#4
Chili said:
The only logic I can come up with is it helps vent the system
Why wouldn't the crankcase breather vent the engine sufficiently for oil drainage? :think: MY YZ-F manual doesn't say to do anything like this during an oil change...
 

oldguy

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#5
Doug my guess is in order to drain the reservoir you need to open the 2nd hole. In order to keep the rotation as friction free as possible the oil is mostly held in the reservoir and only what is needed sits in the sump?
 

Chili

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#6
oldguy said:
Doug my guess is in order to drain the reservoir you need to open the 2nd hole. In order to keep the rotation as friction free as possible the oil is mostly held in the reservoir and only what is needed sits in the sump?
The manual states to remove the TDC plug, then remove the drain plug and the sump plug. There is also the screen and filter stuff etc but for a normal oil change the TDC plug was what had me scratching my head. Obviously no oil comes out the TDC plug so I'm just going to keep rolling paper hats until Rich gets back.
 

XRpredator

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#7
I would do everything the manual says. No questions asked. Otherwise the black helicopters will show up.
 

Chili

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#8
XRpredator said:
I would do everything the manual says. No questions asked. Otherwise the black helicopters will show up.
Pfft, they'll never find me, I lined the ceiling of the garage with tin foil :p
 
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#9
It probably serves as a vent so the oil in the frame can drain into the crankcase more quickly.
 
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#11
Oh, it's a semi-dry sump with seperate oil chambers. I still think the TDC plug hole acts as a vent allowing the chambers to drain quickly into the transmission sump. I can't find any diagrams, though.
 

Chili

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#12
76GMC1500 said:
Oh, it's a semi-dry sump with seperate oil chambers.
If by separate chambers you mean like the Honda's with 2 different filler holes then no that is not the case either.
 
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#14
Chili said:
If by separate chambers you mean like the Honda's with 2 different filler holes then no that is not the case either.
It's a "semi"-dry sump that uses the tranny as the reservoir.
 
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#15
My 06 RMZ450 manual says the same thing, I've done it both ways with no difference noted. If I'm checking cam chain and valves, it's out for the oil change. If I'm not, then it stays in. The only rationale I can think of is it is intended to make you feel more like a mechanic by making you removing things so that you can put them back together :nod: