How long does it take for the oil to start returning.

This area contains links to posts within the forum area on various topics. It's designed to help you find the answers to the most common questions about AJS and Matchless machines.
Only club members can create entries witin this area.
Committee
User avatar
Posts: 2769
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

How long does it take for the oil to start returning.

Postby clive » Thu May 08, 2014 11:16 pm

The question of how long is reasonable to wait for the oil to start returning in the oil tank when rebuilding a heavyweight single seems to come up a lot. As I was trying to seal some major leaks from both pump plates on my 55 G80 engine I thought I would time things.
So I drained the oil tank, then cleaned the oil tank filter during which operation probably half the oil in the filter housing was removed/spilt. I then drained the sump followed by replacing both pump plate gaskets. Despite emptying the oil, both ends of the pump leaked copious amounts of oil whilst the gaskets were replaced.
So in all pretty much like a newly rebuilt engine in terms of little oil in it, except I knew there was still plenty of oil around so did not do what I usually would with a newly built engine (prime the oil by pouring about 4 fl oz down each pushrod tube to make sure the bottom was oiled and which would of course filter through and prime the sump).
But without any oil added how long did it take? Well after 7 minutes of running the engine on a fast tickover even I was beginning to worry though I was sure all was well. The oil level in the tank was clearly dropping but only slowly so not that obvious. Finally after about 8 and a half minutes the oil began to pulse out of the return. The level in the oil tank had probably dropped by 1/3 as the sump filled, the return pocket housing the filter filled, and the oil pipes to the rockerbox refilled.

It would probably take longer on a slow tickover.
clive
if it ain't broke don't fix

Member
User avatar
Posts: 1626
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: How long does it take for the oil to start returning.

Postby ajscomboman » Fri May 09, 2014 6:58 am

I did say it was nail biting stuff! Thanks for taking the time (no pun intended) to time how long it takes for oil to return Clive. When I rebuilt the LCS I followed Itma's advice and filled the filter let it drain down to the sump and filled again. Poured down the push rod tubes and left the cover off and it still took what felt like an eternity for the oil to not only get to the top but also return to the tank.

User avatar
Posts: 900
Joined: Sat Jan 07, 2012 9:57 am
Location: Somerset UK

Re: How long does it take for the oil to start returning.

Postby Les P H » Fri May 09, 2014 7:39 am

What is NOT conducive to a fast recommencement of scavenge oil is that if the breather system is working very efficiently, as it should be, the crankcases are under a negative gas pressure (slight vacuum) This in effect increases the head or height of the oil lift required. If one was to block the breather pipe before starting, this will prevent gas evacuation and additionally will allow pressurisation of the crankcase space due to piston blow by...this will help prime the pump....Once the scavenge pump is primed it should work effectively unless there are problems with its efficiency as mentioned on a very recent other question here...ATB...Les

Committee
User avatar
Posts: 8108
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: How long does it take for the oil to start returning.

Postby Rob Harknett » Fri May 09, 2014 9:12 am

My 1955 G3LS is about the same as Clive's 55 bike, the oil returns more like a waterfall. My 1936 AJS 250 starts to return in less than half that time, the oil pumping straight out, much stronger at least 15 m.m. before falling.
Could be the 1936 AJS return faster and pumps stronger as it has exposed valve springs. There being no supply to the top end of the engine. 1937/38 with semi enclosed springs, has oil supply to the top end. This feeds into the back of the enclosed tappet box and is regulated. Oil return is still stronger than the 55 G3LS

Member
Posts: 11
Joined: Sat Feb 04, 2017 11:49 pm
Location: WESTERN AUSTRALIA AUSTRALIA

Re: How long does it take for the oil to start returning.

Postby Shorty » Tue May 09, 2017 12:12 pm

This scenario also bothered me with my G80CS. I had never started it since importing from the US. Once I went through the timing and carburetor I did kickstart the bike but got jittery when no oil was returning to the tank.
The primary case was off, so I got a big, reversible electric drill, the correct socket for the crankshaft nut and various adaptors to connect it all together.
I removed the spark plug, loosened the rocker feed connecting nut and wound the engine over with the drill. Eventually I got oil to the rockers so was then confident that at least the oil pump was pumping, put it back together and started the engine. Its a simple way to ensure you dont damage the engine, they probably are expensive to rebuild.

Member
Posts: 311
Joined: Sat Oct 26, 2013 8:09 pm
Location: CAMBRIDGESHIRE UK

Re: How long does it take for the oil to start returning.

Postby Triumph-Legend » Sun Sep 03, 2017 10:09 am

Rebuilt motor. I squirt oil all over the rockers, valve springs, down pushrod tubes, oil feed pipes and just about every where else where oil likes to be.
Top up the tank and leave for a couple of days to let it drain through the system and get rid of any air. Fire up the motor and the oil will start to come through in about a minute or two.
As I ride a few bikes, one often gets put to one side for a month or more. I never do anything special to start riding it again. petrol, tickle, set ignition, over compression and away she goes, usually first kick. Give it a minute and check oil returning. Good to go. I never worry about sumping oil unless the machine has stood for several months and the oil level has dropped a bit. Then I may drain the sump. Depends on the oil level, if it's only a bit down, I'll just fire it up and let the motor get the oil back where it belongs, into the tank.

Don't worry if it does not happen as the motor will soon seize thus preventing and further damage. Only joking.

Clive, Finally after about 8 and a half minutes the oil began to pulse out of the return. Ah, there we have it! How long does it take to boil the kettle and make a brew?
Them blokes at the factory weren't so daft were they?
I know, I was once the tea boy, youngest / newest, at an engineering works.

These aren't exactly high performance motors that need constant fettling. If they are fixed right and running, leave it be. It's fine.

Member
Posts: 1561
Joined: Wed Oct 12, 2005 9:45 pm
Location: N YORKS UK

Re: How long does it take for the oil to start returning.

Postby 56G80S » Sun Sep 03, 2017 12:53 pm

Fitted the relined barrel, new piston and everything else replaced as previously. Oil appeared from the return pipe in the tank after about a minute and a half maybe less. I did use plenty of oil in the rebuild process and several squirts from the oilcan down push rod tubes.

Not the same as a complete rebuild but I don't recall it being much longer after I did a complete rebuild.

Plan to do rebuild this winter, so might time the start / oil flow gap!

Johnny B

Committee
User avatar
Posts: 2769
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: How long does it take for the oil to start returning.

Postby clive » Sun Sep 03, 2017 3:00 pm

The reason I started this thread was because members often write expressing concern about how long it all takes. What I was timing was how long it took to see oil return when there was no oil in the sump, no oil in the pump, no oil in the pipes and no oil in the oiltank filter housing and at tickover. As I said normally I prime it all with a rebuilt engine and it does indeed take less time. This timing was without any priming as I knew the big end was well oiled.
clive
if it ain't broke don't fix

Return to Frequent Questions

Who is online

Users browsing this forum: No registered users and 1 guest