Oiling problem

Bob Z. · Apr 21, 2012

I've got a real problem with the oil return on a 1972 750. The crankcases have the breather bolted on the rear.

I had installed one of those magnetic filters on the return line, then wasn't satisfied with the tight area it needed to be located in under the right rear isolastic so I removed it. I ran the engine only a few miles with the filter installed. I reconnected the return line hose from the oil pipe block directly back to the oil tank.

Then I started the engine and checked the return line pipe inside the tank after removing the cap. Lots of oil coming from the breather pipe right at the tank cap opening. What a mess.
But no oil observed coming from the small holes in the return pipe. The rocker feed line did fill with oil.

Seems like the oil is going into the sump but not returning to the tank like it should. Pressure is pushing the oil up the breather line back into the tank.
I confirmed that the oil feed hose and oil return hose are clear. The oil pressure relief valve piston is working.

What has happened?

bill · Apr 21, 2012

IF as you say EVERYTHING is clear from the engine to the oil tank it is time to look at the oil pump. the 72 had NO sump filter, just a large oil pick up hole. it could have pulled a piece of trash into the scavenge side of the pump and damaged it.

comnoz · Apr 21, 2012

I would second Bill's idea of checking the oil pump. If you engine has not had the tabs removed from the cam thrust washer then the common scenario is the tab breaks off and gets sucked up into the oil pump. Usually it breaks the gear in the pump or the shaft. I have also seen pieces of shrapnel plug the channels in the case so the scavenge pump can't work.

It would be hard to imagine how this could have been a result of installing the inline filter. They are very free flowing as they are designed to handle the flow from an automatic trans oil cooler line. They will flow fine even if installed backward but the bypass valve wouldn't work. Jim

Bob Z. · Apr 22, 2012

Thanks for the info.
I'm not faulting the magnetic filter at all, just that is was such a tight fit in that area. The installation and removal of the filter and the required draining of the tank and sump several times during the process may have shaken something up.

I will pull the timing cover and check the pump out. Previously it did have some draindown from the tank to the sump over a few days. I thought the amount was common.

bill · Apr 22, 2012

What you have is 2 separate issues as it is in realty 2 separate pumps. the pressure side is where the wet sumping issue arises and there is a lot more to fixing it than just lapping the body and cover to close up the end clearance. I along with Jim have no use for the anti sump valve BODGE as a way to fix it, but IF you MUST go that route than an oil pressure gauge is a MUST HAVE. Than you have a return pump, like I stated it is 2 separate pumps that happen to be in 1 housing and the side you need to look at is the side with the drive gear NOT the side with the brass cover. I think you will be purchasing an oil pump to fix though :evil:

Bob Z. said:
Previously it did have some draindown from the tank to the sump over a few days. I thought the amount was common.

1up3down · Apr 22, 2012

I would take the oil line off of the return line completely, off the back of the tank and off the banjo

and then blow through it, look through it, is it possibly obstructed?

then with ignition off kick the bike over a number of times

is any oil squirting out of the return line banjo while kicking all over everything?

if yes then your oil pump is not the problem, put a new oil line on and throw the filter used on away

last really dumb question: it is possible you have inadvertently switched the oil lines,

verify which is feed and which is return, yes it is possible to put them on wrong

concours · Apr 22, 2012

1up3down said:
I would take the oil line off of the return line completely, off the back of the tank and off the banjo

and then blow through it, look through it, is it possibly obstructed?

then with ignition off kick the bike over a number of times

is any oil squirting out of the return line banjo while kicking all over everything?

if yes then your oil pump is not the problem, put a new oil line on and throw the filter used on away

last really dumb question: it is possible you have inadvertently switched the oil lines,

verify which is feed and which is return, yes it is possible to put them on wrong

That banjo on the rear of the tank would be the supply, there is no banjo bolt on the return line. He should take the return line off at the engine, fit a short hose into a bucket, see what spits out at kickover, then with 10 seconds of running (having made sure of a full tank for supply.) Post back with results.

Bob Z. · Apr 22, 2012

Here's what I found.

When disassembling the timing side cover every thing looked clean. Then I pulled the pump off and found a 2-inch long string of silicon sealer in the hole.

Perhaps this is a good reminder that when silicon sealer came out in the 70's? it was a great gasket maker, but could make trouble if it circulated in the oil stream.
The oil pump looked OK with a bit of scarring on one of the return gear teeth. I will replace the cam seal, crank timing cover seal, and oil pump seal.

bill · Apr 22, 2012

good find. that is exactly why I do the sump mod different than the INOA-old brit's way as it does give you a sort of filter V just a large open pick up hole. the scary thing is I hope that you got ALL of the silicone out of the sump or it will happen again.

Bob Z. · Apr 23, 2012

A bit of follow-up info.

I did a bit of examining the oil pathways in the Commando crankcases especially at the oil pump mount.
Using my photo, the supply feed to the pump is the double hole with oil weeping out, the return port is the hole to the lower right, and the sump pick up is the next hole with the string of silicon sealant to the right.

So,if the silicon blocked the sump pick up, then oil would not be pumped back into the tank, then the sump would fill with oil and be pressure pushed though the breather line back to the top of the tank.

Am I correct?

pete.v · Apr 23, 2012

Bob Z. said:
A bit of follow-up info.

I did a bit of examining the oil pathways in the Commando crankcases especially at the oil pump mount.
Using my photo, the supply feed to the pump is the double hole with oil weeping out, the return port is the hole to the lower right, and the sump pick up is the next hole with the string of silicon sealant to the right.

So,if the silicon blocked the sump pick up, then oil would not be pumped back into the tank, then the sump would fill with oil and be pressure pushed though the breather line back to the top of the tank.

Am I correct?

Seem about right. Locical. By George, I think he's got it.

batrider · Apr 23, 2012

I had some metal junk picked up by my scavenge passageway in the early days (ate the pump scavenge gears) and so I did a good flushing with kerosene. I removed the sump drain plug and squirted it under high pressure into the scavenge passage (like a reverse flush) and got some more metal particles out from the sump. It would have been more "proper" to split the cases etc but I took the risk and am still riding it like that 20K miles later.

Bob Z. · Apr 23, 2012

That makes sense that the oil scavenge from the sump may have some metals debris that can cause damage as they pass through the pump.
I checked on some of my used parts and the scavenge gears are always the ones with some marks.

My 1972 has only the small crankcase drain plug, no gauze sump filter like later models.

pete.v · Apr 23, 2012

That pump is screwed and will never creat the needed pressure. Gears in a gear pump need to be almost pertect , or at least very good, along with the seal point they work against. Look for a good use unit on ebay.

batrider · Apr 23, 2012

I replaced the oil pump because it was really much worse than yours. The gears were badly chewed. These pumps are very available usually much less than new on eBay and I've accumulated some good spares after buying the brand new one. This was back in the early '80s. I also have the small drain plug. 1972 was the only year for that.

I'm not sure what it picked up but it looked shiny and hard. I'd be a little worried about all that silicone sealer floating around and maybe blocking other places in your engine.

DogT · Apr 23, 2012

Unless you know the history on this engine, I'd be tempted to break it open and clean it up. Or take a chance and keep a good eye on the return oil, but how can you do that riding? My 2 c.

Dave
69S

pete.v · Apr 23, 2012

There are 2 maybe 3 grub screws placed at end points of oil tunnels to block off where they were machined. They are usually punched to keep the from backing out.

Search for these and open them up to reveal access. Not all have them but I do in the front below the engine mount in line with the drain plug.

I do not know if you want to blow in there, I sure wouldn't, but sucking may be a good thing to do.

Bob Z. · Apr 23, 2012

Your point is very good.
Here is a photo of the blanking screw on a 850 case for the drilled passage from the oil pump mount to the sump pickup.
I will flush with solvent down the scavenge hole on the oil pump mount and drain at the crankcase drain plug.

I wonder what will emerge.
I'm really trying to NOT split the cases on this issue.
I'll bet the pro engine re-builders could tell some horror stories about what they find when they open up old engines!

Oiling problem

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