central oil tank

Status
Not open for further replies.
ILLF8ED

ILLF8ED

Joined
Dec 30, 2003
Messages
3,662
Country flag
Working on this ‘69 750 S I’m wondering how the oil is drained on the central oil tank when it’s oil change time. There is no drain plug on the tank.
Dave, DogT, I’m sure you know.
 
illf8ed said:
Working on this ‘69 750 S I’m wondering how the oil is drained on the central oil tank when it’s oil change time. There is no drain plug on the tank.
Click to expand...

The oil feed filter bolt is the drain.
 
When I still had the central tank I would just detach the oil line from the junction block, then siphon out the remaining oil from the bottom of the tank
 
acadian said:
When I still had the central tank I would just detach the oil line from the junction block, then siphon out the remaining oil from the bottom of the tank
Click to expand...

^^^^^^ this.

Then every few oil changes, you unbolt the bottom bolt on the lower oil line and swab out the bottom of the tank to get any sludge that has settled out. I also run a transmission filter on my return line to pick up any magnetic particles and debris. It's not a stock application by any means, but Jim Comstock recommended it, so... The early bikes don't have a paper filter, only the screens on the oil tank ports, so an extra filter with an internal magnet can't hurt...

Here's mine.

https://www.accessnorton.com/Norton...nstall-for-a-70-model-central-oil-tank.28202/

.
 
Yes draining a central oil tank is sh-t, one of the reasons I sold my '70 S, the oil tank on my '69 FB is a lot nicer.
 
I used to drain it out of that large screen 'bolt' with a 'sheet' of foil or similar. But then I got wise and disconnected the junction block as others have said. But the tank usually needs cleaning, so after that I also take out the screen and use mineral spirits (or gas) to clean out the tank with a shotgun mop. It's always a mess no matter how you do it. You just need to clean up afterwards. My zero turn and standby generator are the same way, always a mess, it's hard to believe where these guys put the oil drain. The easiest one is the wife's 3.6 Subie Outback, nice ground clearance, I don't even have to jack it up. It takes 7 quarts when drained properly.
 
DogT said:
I used to drain it out of that large screen 'bolt' with a 'sheet' of foil or similar. But then I got wise and disconnected the junction block as others have said. But the tank usually needs cleaning, so after that I also take out the screen and use mineral spirits (or gas) to clean out the tank with a shotgun mop. It's always a mess no matter how you do it. You just need to clean up afterwards. My zero turn and standby generator are the same way, always a mess, it's hard to believe where these guys put the oil drain. The easiest one is the wife's 3.6 Subie Outback, nice ground clearance, I don't even have to jack it up. It takes 7 quarts when drained properly.
Click to expand...
Ah remove the junction block. Risk though of wearing the threads in the alloy crankcase. Could just remove the strainer at the bottom of the crankcase and wait for all the oil to sump. Just kidding.
 
possm said:
Yes draining a central oil tank is sh-t, one of the reasons I sold my '70 S, the oil tank on my '69 FB is a lot nicer.
Click to expand...
Tried fastback body but don’t care for the look. I’ll suffer the messy oil change. Comfortable seat though. Came from Leighton.
central oil tank
 
illf8ed said:
Ah remove the junction block. Risk though of wearing the threads in the alloy crankcase. Could just remove the strainer at the bottom of the crankcase and wait for all the oil to sump. Just kidding.
Click to expand...

NO, you don't remove the junction block at all....

You remove the lower hose clamp on the hose that leads to the junction block pipe, then pinch the hose with a hemostat and pull the hose off the junction block pipe and direct it into a funnel leading to your drain pan before you unclip the hemostat to let the oil flow out of the tank. The amount of oil that misses the funnel is tiny once you've done this procedure a few times.

Having owned my '70 commando for 40 years, there are issues with early bikes that should be rectified if you're doing a total restoration, like crankcase breathing, but there's nothing inherently bad about the central oil tank, other than it lowers the capacity of oil by about a half of a quart more than late model oil tanks.

There are other early bike flaws like... the non-box style headsteady sucks, engine cradle single bolt swingarm tube, no paper oil filter, 12 volt coils, timing disc breather, frame cross member blocking the use of Jim comstock's sump breather... and more if I keep thinking about it... Utimately, all the early model flaws can be mitigated to the point where I don't ever think... "I wish I had a late model commando instead of the one I have."
 
Status
Not open for further replies.
Back
Top