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Engine oil site glass question

N

nickrides

Nick Kennedy
Hypothetical question:
I'm cruising down the hwy on my 1990 75 Rt and the oil site glass blows out.
I carry a metal plug to temporarily put in there just in case, but not a site glass.
So If the oil blows out to the bottom of the hole and I tap in my metal cap, how much oil is anyone's wild ass guess should I put in there to keep moving?
Thanks in advance!
Nick
 
I don’t know much about brick motors but on boxer motors from full to not showing in sight glass is like 8 ounces or so. That’s from memory so take that into consideration. With bike level was oil up to lower edge of sight glass hole? If so I would think it would be ok for a short ride to get it home or off the side of the road. Much further would certainly make me nervous. Low oil levels scare me.
 
If it ran out to the bottom of the hole, but did not blow out more oil than that you still have at least 3 quart of oil in the engine. So plug the hole with a freeze plug and go to the nearest auto parts store, add 1/2 quart for good measure and drive on. In the real world it may spew more oil than that if it blows going down the road. That said, loss of the sight glass on a K75 is so rare as to be nothing to worry about. It is the big twins that have the issue. On a K75 pistons are going in and out not at the same time so crankcase pressures are very low.
 
OK
Thanks for the responses
Last night I was cleaning all the junk that accumulates in my side boxes and I have a freeze plug in there for back up and was wondering..
I also carry a Z line, that and a CC and a headlamp, I'm ready
Maybe I should put in some dehydrated water I've been reading about too.
Nick
:eat
 
All i carry is the BMW tool kit and a tire plug kit, (I had to use the plug kit recently). Anything more and I would just pull out the mobile phone. I've never even thought of the sight glass blowing out.
 
PGlaves said:
If it ran out to the bottom of the hole, but did not blow out more oil than that you still have at least 3 quart of oil in the engine. So plug the hole with a freeze plug and go to the nearest auto parts store, add 1/2 quart for good measure and drive on. In the real world it may spew more oil than that if it blows going down the road. That said, loss of the sight glass on a K75 is so rare as to be nothing to worry about. It is the big twins that have the issue. On a K75 pistons are going in and out not at the same time so crankcase pressures are very low.
Click to expand...

Paul or Lee, does the above apply to the K100s?
 
Paul_F said:
Paul or Lee, does the above apply to the K100s?
Click to expand...

Yes. For every piston going inward there is one or more going outward toward top dead center so crankcase pressures are minimal. And sight glass placement in the engine case is about the same.
 
IF you were going somewhere that you would be concerned about the oil plug blowing out, a better solution than a freeze plug might be an Oatey mechanical plastic pipe test plug. They are made for temporarily plugging house drain pipes so they can be pressure tested. They have red plastic on each end with a rubber center that is expanded by a large wing nut.

If you are out in the boonies, you can plug the hole. Then start the bike and see if there is still enough oil in it to keep the oil light off. Then you can gingerly make it to where some oil is available. Pull the plug out and fill to the bottom of the hole, put plug back in and add a bit more than 1/2 qt.

My question is what is the first sign that the sight glass has popped out? The exhaust is on the other side so I don't know how much smoke there would be. Oil on the rear tire may be noticed in corners.

I think I know! Since the sight glass is a huge hole into the crankcase, the amount of air getting into the crankcase and then getting sucked through the crankcase vent hose into the intake plenum will lean out the mixture to the point where the motor will shut off (at least at lower rpm).




:dance:dance:dance
 
Last edited:
98lee said:
My question is what is the first sign that the sight glass has popped out? The exhaust is on the other side so I don't know how much smoke there would be. Oil on the rear tire may be noticed in corners.
Click to expand...

No experience with a K bike blowing a sight glass but I have two direct experiences with Oilheads. What I tell people is to remove the oil filler cap while the engine is running. That makes a distinct sound, and if they ever hear it again to shut the engine off immediately and investigate. As for running, the behavior with the sight glass blown is about the same as with the oil filler removed. Try it.
 
98lee said:
IF you were going somewhere that you would be concerned about the oil plug blowing out, a better solution than a freeze plug might be an Oatey mechanical plastic pipe test plug. They are made for temporarily plugging house drain pipes so they can be pressure tested. They have red plastic on each end with a rubber center that is expanded by a large wing nut.

If you are out in the boonies, you can plug the hole. Then start the bike and see if there is still enough oil in it to keep the oil light off. Then you can gingerly make it to where some oil is available. Pull the plug out and fill to the bottom of the hole, put plug back in and add a bit more than 1/2 qt.

My question is what is the first sign that the sight glass has popped out? The exhaust is on the other side so I don't know how much smoke there would be. Oil on the rear tire may be noticed in corners.

I think I know! Since the sight glass is a huge hole into the crankcase, the amount of air getting into the crankcase and then getting sucked through the crankcase vent hose into the intake plenum will lean out the mixture to the point where the motor will shut off (at least at lower rpm).




:dance:dance:dance
Click to expand...

Hi Lee, what size Oatey plug would you choose in such a circumstance. I'd never heard of them, but now I want one in the bikes permanent kit carried in left pannier. My bike is a 2012 r1200gs

thanks in advance
 
PGlaves said:
No experience with a K bike blowing a sight glass but I have two direct experiences with Oilheads. What I tell people is to remove the oil filler cap while the engine is running. That makes a distinct sound, and if they ever hear it again to shut the engine off immediately and investigate. As for running, the behavior with the sight glass blown is about the same as with the oil filler removed. Try it.
Click to expand...

Paul,

I just tried it on a K75. You can't here any noise from the oil filler over the Jetson's hovercraft sound of the motor.

But, unlike an oilhead that has an O2 sensor that would compensate (to a degree), the K75 has no way of compensating for the extra air. I didn't try it on the road, but after fully warming up the engine and then locking the throttle at 4k rpm, I pulled the filler cap. The rpm immediately dropped to 1500 and ran very poorly. I would imagine that the immediate loss of power and throttle response would be very noticeable.

Maybe you could try it on the road and give us some feedback. My bikes are currently blocked in my shop by construction material for my house remodel.:dunno



:dance:dance:dance
 
brownie0486 said:
Hi Lee, what size Oatey plug would you choose in such a circumstance. I'd never heard of them, but now I want one in the bikes permanent kit carried in left pannier. My bike is a 2012 r1200gs

thanks in advance
Click to expand...

Brownie,

Disclaimer: I don't KNOW if these plugs will work as, like Paul, I've never seen a Brick motor with a blown out sight glass. I don't know if there is a lip in the block that is a smaller I.D. than the rubber O.D. of the sight glass. So I am just assuming, and you know how well that works.


I don't know the diameter of any sight glasses other than early K bikes which are a hair bigger than 1 1/2".
Paul should be able to tell you if there is a lip inside the sight glass hole of your bike. If there is no lip, just measure the O.D. of the rubber surround.

https://www.homedepot.com/p/Oatey-1-1-2-in-Gripper-Plastic-Mechanical-Test-Plug-33400/100342630






:dance:dance:dance
 
Thanks Lee, hopefully Paul or someone else can clarify. I think it's worth having such a small light part in the kit on the bike. If needed, it would save the day and a tow to a shop.

ETA, I just went out to the garage and measured the sight glass. Appears to be 1.5" in diameter. Give or take a 1/16th" either way.
 
98lee said:
Brownie,

Disclaimer: I don't KNOW if these plugs will work as, like Paul, I've never seen a Brick motor with a blown out sight glass. I don't know if there is a lip in the block that is a smaller I.D. than the rubber O.D. of the sight glass. So I am just assuming, and you know how well that works.


I don't know the diameter of any sight glasses other than early K bikes which are a hair bigger than 1 1/2".
Paul should be able to tell you if there is a lip inside the sight glass hole of your bike. If there is no lip, just measure the O.D. of the rubber surround.

https://www.homedepot.com/p/Oatey-1-1-2-in-Gripper-Plastic-Mechanical-Test-Plug-33400/100342630

:dance:dance:dance
Click to expand...

As far as I know all of the sight glasses BMW has used since the '80s have been the same size, except on some G and F bikes like my G310GS. It is smaller.

And yes, on an R1100 and R1150 engine at least there is an inner lip that prevents the sight glass from being driven too far into the engine case.
 
PGlaves said:
As far as I know all of the sight glasses BMW has used since the '80s have been the same size, except on some G and F bikes like my G310GS. It is smaller.

And yes, on an R1100 and R1150 engine at least there is an inner lip that prevents the sight glass from being driven too far into the engine case.
Click to expand...

Would you think that 1.5" Otey plug would work? Just a best guess is fine sir, thanks
 
Oatey makes some great plumbing solutions. Those interested may want to do a google search for “rubber freeze plugs”. I have used these rubber freeze plugs in both the intended use and in other applications.
OM
 
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