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B50 oil pressure/pump #740263
06/29/18 7:47 pm
06/29/18 7:47 pm
Joined: Sep 2015
Posts: 14
Georgia USA
J
Joel Greene Offline OP
BritBike Forum member
Joel Greene  Offline OP
BritBike Forum member
J
Joined: Sep 2015
Posts: 14
Georgia USA
Hi guys, been awhile since I posted here. I recently bought a B50 with 9330 original miles and have been trying to determine the engines condition before I get too far into making a project out of it. It was siting for several years so it took a little doing to get it going, but finally got it running pretty good. One thing I noticed was what seemed to me to be a very low amount of return oil to the tank(frame). Pulled the line off and ran it into a pan to be sure there was no obstruction, there wasn't any. So, I removed the plug in the case that was originally for an oil pressure switch and screwed a manual gage directly into it. With cold oil it was showing 10 psi at idle and wouldn't exceed 20 psi when revd up. After the oil began to warm up it showed nearly no pressure at all. I had previously dismantled the pressure relief valve and cleaned it, it was pretty dirty, but have no way to accurately test it. So the questions are 1) is there a known acceptable range for oil pressure on this motor? 2) are the pumps rebuildable? I know replacements are expensive and hard to find. 3)any other thoughts? Thanks , Joel

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Re: B50 oil pressure/pump [Re: Joel Greene] #740277
06/30/18 2:11 am
06/30/18 2:11 am
Joined: Oct 2008
Posts: 1,684
Canada
L
LarryLebel Offline
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LarryLebel  Offline
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L
Joined: Oct 2008
Posts: 1,684
Canada
The return side of the oil pump has a much higher capacity than the delivery side so the oil returns to the oil tank in irregular spurts so what you are seeing might be OK. I believe the oil pressure will be essentially zero because your B50 has a roller bearing big end. I could be wrong on this because with zero pressure it doesn't make any sense to have an oil pressure gauge/light take off.

Last edited by LarryLebel; 06/30/18 2:12 am.
Re: B50 oil pressure/pump [Re: Joel Greene] #740290
06/30/18 5:23 am
06/30/18 5:23 am
Joined: Dec 2004
Posts: 9,483
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,483
Scotland
There is no oil pressure to detect as its a roller big end there is no back pressure unlike on a shell bearing, the oil pump is also lower capacity for the same reason.

Worry about something else.

Re: B50 oil pressure/pump [Re: Joel Greene] #740493
07/02/18 11:52 am
07/02/18 11:52 am
Joined: Mar 2002
Posts: 529
NY
OriginalScott Online content
BritBike Forum member
OriginalScott  Online Content
BritBike Forum member
Joined: Mar 2002
Posts: 529
NY
I recently rebuilt the oil pump in my B50. The hardest part was undoing the 4 screws that hold it together. It only needs to be cleaned and put back together unless you find chipped or missing teeth on the gears. If you do pull it apart there may or may not be thrust washers under the 2 inside gears. Mine did not have any but I guess the early B50 pumps did. The return is mixed with air so don't expect a steady stream of oil. It's more like spurts.

Scott

Re: B50 oil pressure/pump [Re: Joel Greene] #740506
07/02/18 2:17 pm
07/02/18 2:17 pm
Joined: Aug 2005
Posts: 1,487
melbourne florida
B
bodine031 Offline
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bodine031  Offline
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B
Joined: Aug 2005
Posts: 1,487
melbourne florida
Being your in GA. check in at Rodi's with Beno or Wobbly Richard

Re: B50 oil pressure/pump [Re: Joel Greene] #740959
07/06/18 2:42 pm
07/06/18 2:42 pm
Joined: Jun 2002
Posts: 934
Jaffrey, NH, USA
Peter Quick Offline

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Peter Quick  Offline

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Joined: Jun 2002
Posts: 934
Jaffrey, NH, USA
I have found that it is best to not molest / take apart a unit single pump that turns freely in ones hand. Sometimes a pump will seem stiff when turning. Before taking apart first try warming it up (propane torch seems to work) to see if it is just gummy oil deposits in it that make it stiff . If that is all it takes to loosen just run some oil through it to clean it out. The gears inside the pumps really do not seem to ever wear out so taking apart to inspect for wear is in general a bad idea. The gears seem to wear in with each other and taking apart and putting back together can easily transform a pump to a crunchy binding problem. At least in my experiences.

The pot metal pumps are a problem from the start and the bodies warp and the gears bind and stick. There is really no way to fix this issue at home (unless you are an experienced machinist with the right equipment). Best to get a smoother turning used pump or a more expensive NOS one and replace.

The three bolt OIF iron unit single oil pumps rarely cause any problems. Just flush out and put back in.

And as Kommando said, roller bearing big ends do not need much oil pressure so the issue of an oil pressure gauge on a B50 is only going to torment someone who puts one on. I get calls about this a few times a year from folks wondering what is wrong with their B50 after they decide to add an oil pressure sender to the available hole in cases. Does the hole make any sense? Consider this. The inner timing cover for the B50 and B25 is basically the same casting that is then machined for the different kick start set ups. The B25 was deemed to need an oil pressure sender so the hole is there. Don't need one for the B50 so it is easier to blank off the hole with a plug rather than have a new casting. So it depends on how you look at any number of things BSA did to know if what they did made sense or not and for whom. Once you start looking at it from a production and cost savings perspective more things they did make sense (customers be damned).

Peter


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2500 BSA part numbers with inventory in stock just for the unit singles!

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