Oil stuck in back compartment of GL1000

[cfairweather]

Several months ago, I brought up a problem concerning oil that gets stuck in the back of the engine. When you change the oil on the GL1000, you cannot get it all out because at least half a quart gets stuck in the rear compartment. On one of my current project bikes, I decided to prove my point, so I put the bike on a flat surface and drained the engine using the drain plug and the filter. I let it all drain out for weeks to make sure it was bone dry. Then I removed the engine and removed the rear cover. I captured all the oil I could get out of the rear compartment and then poured it in an oil container to see how much was in there. It turned out to be almost 3/4 of a quart. I have no idea why Honda did not install an oil plug in the rear compartment, but I believe this is a good thing to add when you have the engine out.

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[Paola Zago]

Maybe I say a stupid thing, and try to put a shim, a wooden plank under the rear wheel in order to tilt the motorcycle forward?
or put yourself on a slightly inclined plane with the front end downwards, can't that favor the release of that remaining oil?
Paola (Italy)

[ericheath]

Not sure if this applies, but years ago someone here posted that to drain the oil more completely, you let it drain the bulk by gravity, when it has seemingly stopped, turn the kill switch to “off” and crank the motor over a few seconds. Wait for it to drain some more. Repeat as necessary. It is surprising how much will come out with each cycle. I’m guessing the scavenge pump is finishing its job without getting fresh oil.

[cfairweather]

Paola- That is a good idea and I have actually tried to do what you suggested. It helped; however, you would have to get the bike at a steep angle to get most of the oil out. I think a drain plug is a better way if you have the engine out of the bike. I will be finding a good place to install one in the near future.

Eric- That would certainly get more oil out, but at the cost of turning the engine without oil pressure. It wouldn't hurt for a few seconds, but it would take a lot of cranking for the scavenge pump to get it all out. The scavenge pump simply pumps the oil over the edge of the rear compartment to the main compartment.

[Old Fogey]

Some time back, Randakk had a gearchange problem which turned out to be caused by a high oil level in the clutch housing.
You can read the story here: https://www.wingovations.com/scavengepumpproblem

[Fred Camper]

Thank you for posting Old Fogey. As my rear cover is off for clutch update, now is a good time to replace that gasket with the modified one.

And when I took my rear cover off, only about 1/2 cup came out, so I do think other may have the gasket issue.

[tlbranth]

I have no idea why Honda did not install an oil plug in the rear compartment

Honda didn't design this engine. Satan did.

[Whiskerfish]

[Lucien Harpress]

There's a joke about "car guys" in here somewhere, I know it.

[Fred Camper]

Just opened my clutch savage pump and the gasket was like new and the rotor and mating surface looked great and no debris present. So if your pump is working well like mine, only 1/2 cup of oil will drain from the rear cover. Replacing the gasket with a new one that is modified per Johns post to keep my system working well for a long time.

[cfairweather]

Fred- I am not so sure that having a 1/2 cup of oil is common. Before this project bike, I have never measured the oil that comes out of the rear compartment, but I am certain that on all the GL1000s that I have done, it has been more than that. From my experience, about 1/2 quart is very common. I have known about that gasket issue for years, but in all the engines I have taken apart, I have never seen even one where the gasket blocked the passage. I will let everyone know if this particular bike has the gasket problem in a day or so. If it doesn't, I am curious why yours has 1/2 cup and this one has almost 3/4 of a quart. Doesn't make any sense to me.

[Fred Camper]

I did let mine drain for days before removing the rear cover. I did remove the clutch before the rear cover and of course it was wet and not measurable. So you may be correct that over a cup is more common.

[cfairweather]

I just removed my rear pump and the gasket was flat as a pancake. It looked just like all the ones I have seen in the past. I have never seen this gasket block or partially block the hole. By the way, you can trim this gasket without disassembling the oil pump. Just use a sharp, thin, narrow craft knife and it will save you from taking it apart. Unless you plan to rebuild the pump, it won't gain you anything to take it apart. So I go back to the question, why did Fred's have less than a cup and mine had over 1/2 quart. Could it be he has a better pump? Could it be that for some reason, not as much oil is getting into the compartment on his bike? The oil has two entry points. It can get through the ball bearings. Oil can get on the drive shaft spring and get slung into the rear compartment. When you do an oil change, some of the oil goes into the rear and some of it goes into the main compartment. The pump is the primary way the oil is transferred to the main compartment but there is at least one place where the oil can drain back to the main compartment. I doubt if much oil drains back to the main compartment because that hole is in an area of the rear compartment that is starved for oil (near the starter clutch and alternator). I don't understand this one.

[redglbx]

So I’ve been reading this thread from the start with interest, but I always close the thread with the same question, ,,”what harm will this do really” ??

Not trying to be a smart azz here but just trying to understand the problem.

[cfairweather]

RedGLbx- Good question. My initial goal with installing a drain plug was to get as much dirty oil out as possible because I was seeing 1/2 to 3/4 of a quart of dirty oil left in the engine. If Fred is right about the normal amount being about 1/2 cup, then it is not a problem and no plug is needed. I honestly don't know know what is normal at this point but I am adding a drain plug. I don't think this is a big deal one way or the other. Most of these threads do nothing but keep us busy .

The more I look at the design, it makes me wonder how important that scavenge pump really is. After looking at the engine again, I think Honda decided to add the scavenge pump because the clutch would be too deep in oil.