Ok boys, I've had the same problem and I got the thin into the shop. The shop isn't big on custom bikes but he says I need to have a "catch can" fabricated for my blowing oil problem? Does this make sense? The bike is a rigid so I understand why some oil would blow out o the vent but I figured it wouldn't need a catch can.... My oil tank is just a barrel tank mounted under the seat. Two nipples on the top, one being a vent I assume (where the oil is coming out) and one on the bottom. The old guy said a friend of his that built choppers in the 70's suggested it after looking at it for 2 seconds. Thanks..... Totally in over my head I think.
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Well, the stock tank has an internal seperator/baffle setup that keeps actual oil from leaving the oil tank through the vent. I have used "barrel" tanks before, one thing to check is that you are not overfilling the tank to start with. Oil does expand quit a bit when it gets hot. I over filled mine the first time and pucked oil out the vent first time the oil got hot...like after a run on the interstate. Another thing to check is to see were the oil return is pointing in the inside of the tank. I fixed one that would spray the oil straight up in the tank and it splashed all over and some found its way out the vent. The 750's have the oil circulating pretty good in and out of the tank so the oil really gets to splashing around. I dont run a catch tank on any of my builds and dont have any problems other than a drip or two once in a while. I guess a catch can would be something to try, but I think your tank may be on the small side and you are overfilling it. But without being there in person its kind of hard to say but maybe this will give you some ideas.
Paul Barter
CB750 New member
Hi guy's, I've just joined and this is my first post. About 30 years ago I re ringed a cb750 and had a similar thing occur, my situation was first thing I noticed was that the oil light remained on at low rpm it also pressurized the oil tank. never did sort it out but what I did was block off the rocker cover breather hose at the oil tank and placed the breather tube into a catch bottle. Problem solved. Fast forward to 87 when I purchased a 69 cb750 from interstate sight unseen, I had a friend collect the bike and store it for me until I had time to collect it. 1 year later when I collected it my friend informed me that this bikes oil light wouldn't go out either. so when I got it home I tore down the engine and found badly worn rings, the standard bore was still within wear limitations so I fitted new rings and a few other worn items, when I fired it up I still had the same problem and yes checked all the lines were clear and previously having been a Honda mechanic I had rebuilt loads of these engines and have only had this fault happen twice and to this day the ko still has the breather tube into a catch bottle and has done 15,000 miles without a miss. Any ideas? Maybe it's related to your problem,did your oil light come on (pressure related) and did you ever get a look in the tank?
