I recently bought a 1972 commando combat. The engine was reworked by the previous owner with the usual modifications to improve the combat engine includeing relocation of the engine breather to the back of the timing cover. What concerns me is that the engine oil level as measured with the dipstick built into the oil tank cap was low when I got the bike (below the "low mark"). I figured there must have been some wet sumping loss and checked it again after running the engine for a few minutes. I checked the level with the engine not running but warm and the bike on the center stand and it was still low (below the "low" mark). I added just shy of a quart of expensive synthetic oil bringing the level to about 3/4 of the way up between the upper and lower mark. After an exhilerating half hour ride; 6000 rpm, max throttle, and a lots of hard sweeping turns I am completely in love with the bike but I thought the rear end felt a bit squirrily in hard turns and back at my garage I saw why. From the center stand back the bike was covered in oil. Oil had drenched the rear tire and was thown up under the fender which was dripping all over the rim and the swingarm. With that much oil on the tire and the way I had been riding I felt lucky to have made it back in one piece. I looked everywhere for the source of the oil. The engine was tight and dry. All the oil lines are new and although oil had splashed everywhere I am pretty sure they aren't leaking. The chain oiler pipe has been blocked off and when I checked the oil level in the resevoir I found the extra quart of oil I had added had been belched back out I think through the vent tube which exits beneath the frame just behind the swingarm and which connects to the neck of the oil resevoir just below the cap. So what's going on? Is the dip stick wrong and I over filled the resevoir? Am I not checking the oil level properly? I can't imagine putting more oil in it again but it is nerve wraacking to ride around with the oil level barely touching the bottom of the dipstick? Does anyone know what the distance should be between the top of the fill neck and the suface of the oil so I can calibrate my dip stick? Is there some other unfathomable idiosyncracy to the bike that I need to add to the laundry list of unfathomable idiosycracys I already know about. Honestly, my wife is worried about my relationship with this bike and I must say I'm a bit concerned myself. This bike is like the wost girlfriend I ever had. Cantankerous, demanding, unreliable and more expensive than I can possibly afford but so damn pretty I'll put up with almost anything knowing she could leave me flat at any time... did I say "she"? O.K... so maybe I need a shrink not a mechanic.
#1. "RE: Engine Oil Level" In response to Reply # 0
Are you sure the oil tank isn't cracked where the rubber mounting bolts affix? I've had to repair 3 seperate Commando oil tanks over the years that cracked from vibration. It wasn't until I cleaned things up that I could see the source of the leak. As you said, with all that oil over the rear wheel you were very lucky not to go down.
#2. "RE: Engine Oil Level" In response to Reply # 1
Thanks for the suggestion. There is no crack visible on the tank. I'll pull it off this weekend and pressure test it (although the tank shouldn't be under any pressure when in use). Do you have any idea what the correct oil level should be? I'm wondering if I might have the wrong dipstick for this tank?
#3. "RE: Engine Oil Level" In response to Reply # 2
Since the dipstick is part of the oil tank cap I doubt that you have the wrong part. The full line indicator is between 1 and 1.5 inches below the oil return outlet opening on the inside of the tank. With the motor running you should see a steady stream from the scavange side of the oil pump flowing with the cap removed. Since the scavange capacity of the pump is greater than the supply capacity, you will have the highest oil level with the bike running. If the oil level is at least an inch below the return outlet with the engine running you should be fine. If it is much higher than this you could get oil leaks from the tank neck. Ultimately you will have to clean everything up and just observe where the leak originates. There is a fascinating number of places these old bikes can leak from. good luck
#4. "RE: Engine Oil Level" In response to Reply # 0
"This bike is like the wost girlfriend I ever had. Cantankerous, demanding, unreliable and more expensive than I can possibly afford but so damn pretty I'll put up with almost anything knowing she could leave me flat at any time... did I say "she"? O.K... so maybe I need a shrink not a mechanic."
Leking oil? Then you have not achieved norton mechanic status. All bugs and upgrades that are above and beyond good stock condition.
#5. "RE: Engine Oil Level" In response to Reply # 4
I have fully inspected the oil tank. It is not leaking. The oil is definitly being lost through the overflow tube. The question is why? After riding a few miles the tank seeks it's own level with oil just touchin gthe bottom of the dipstick. If I add any more it will come out the overflow tube. I tried to measure the distance between the stream of return oil and the oil surface with the engine running. I think it is a little over 2 inches but the oil was hot and my temper was hotter so I'm not sure. I have included a picture of my dipstick/cap with a ruler along side it. I also included a picture of the bike because I'm so proud of it and a picture of my dog because he helps with all my heavy thinking. I have now got more than 50 miles on the bike with what may be a low oil level. I suppose if something bad were going to happen it alreadsy would have but I would be a lot more comfortable if I knew what was going on. Thanks for all the responses.
#8. "RE: Engine Oil Level" In response to Reply # 7
In rereading your original message you stated that the oil was
flowing from the overflow tube which " connects just
below the oil fill cap" . The front facing tube that
exits just at the filler neck is the crankcase breather hose
not an overflow hose and should connect to the inside timing
cover. The oil tank vent hose connects at the top center of
the oil tank and should connect to the back of the stock air
filter assembly or under the frame if you have removed the
stock air filter. If you have the hoses reversed you may be
getting splash from the return outlet spilling out the
adjacent crankcase vent opening. If I understand your
description this may be worth checking.
#9. "RE: Engine Oil Level" In response to Reply # 8
Yes! That solves the problem. I moved the vent pipe and the breather pipe to the proper positions as per your wise instruction and now my bike holds a full load of 50 wgt with no leaking. Thank you very much for paying such close attention to my problem.
#10. "RE: Engine Oil Level" In response to Reply # 9
Glad to hear you can now enjoy your fine machine. One other
note from your original posting.....You said that you topped
off the oil tank with synthetic oil. Do not mix sythetic and
nonsynthetic oils. I don't want to start another oil
preference thread here but with frequent oil changes
synthetic oil doesn't seem necessary on the Commando.
#11. "RE: Engine Oil Level" In response to Reply # 0
Since it sat for a while before you added oil it may not have been actually low because the oil was probable sitting in the bottom of the crank case. So..you most likely over filled it and that was what it was spitting out. Before you check your oil it is generally a good idea to turn the engine over first. Then the oil will be pumped back into the tank for a more accurate reading.
