BSA M33 oil ways

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BSA M33 oil ways

Postby Albertorondm » Wed Oct 17, 2012 4:53 pm

Hi
I'm new to the british bike scene and have purchased a BSA M33 ohv. The oil pump returns from the sump to the oil tank ok, but I'm questioning how much oil should be returning from the cylinder head. I have loosened the two banjo's that return oil from the rocker arms and also another return from the cylinder head, alas no oil seems to be coming out of them when I start the bike up. How can I tell if enough oil is getting to the top of the engine????
Cheers Albert
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Re: BSA M33 oil ways

Postby Welsh Wizard » Thu Oct 18, 2012 4:17 am

If memory serves correct
the supply route should be

at the oil tank, where the oil returns there should be a banjo that takes some of the returning oil to the top of the head , this then goes into the ends of the rocker shaft.

after oiling the rocker shaft, the oil then goes down through the engine into the sump where it is scavenged by the pump and returned to the oil tank, most of the scavenged oil returns to the tank only a small amount every gets returned to the rocker shaft.

So you should not get much flow, but there should be some, so you will need to check if the rockers are covered with oil after you have had it running for a few minutes.
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Re: BSA M33 oil ways

Postby fido » Thu Oct 18, 2012 8:58 am

Yes, the banjos on the rockers are supplying oil, not returning it. I wonder if the copper pipe is blocked? You could take it off and flush it through with paraffin. As it is on the return part of the main circuit there is not enough pressure there to clear any blockage.
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Re: BSA M33 oil ways

Postby Tman » Thu Oct 18, 2012 2:20 pm

My Empire Star was a variation on this engine, and the (lack of) oil flow to the rockers bothered me too, so I made new banjo's, oil lines and bought new banjo bolts. Result...much the same, although loosening the banjo's had oil coming out OK.
Putting an airline and oil can on the ends of the rockers showed they were the obstructions to the flow, but stripping them also showed oil grooves cut in the shafts.
Anyway, when I went on the maiden voyage on her, oil was clearly reaching the rockers all right, as 1) 75+ miles would have seen the rockers squeaking big time, and 2) oil was smearing down the outside (leaking gland) of the big ol' pushrod tunnel on it's way back to the sump.
I can only think that on these early OHVs the upstairs oiling issues hadn't been addressed yet, and the concept that this oil performed a cooling function too hadn't been considered.
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Re: BSA M33 oil ways

Postby Albertorondm » Thu Oct 18, 2012 3:33 pm

Smashing. thanks for the info, I just prosumed that the pipe was a return as its fastened to the return from the sump to the tank. I'll have an hour on it tonight and see how we can't make some improvements.
The larger diameter pipe that runs from the head to the crank casing can I prosume this is just a return?
I've spent far too long messin with jap stuff, its like going back to school. Inches, BSW???

Thanks again Albert
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Re: BSA M33 oil ways

Postby Paul in NZ » Thu Oct 18, 2012 7:05 pm

Open the tappet covers and see if there is oil in the top end. Its the only way it gets there so if its laying about in pools you are sweet. If you are still worried, start the bike and when the oil is returning... Put your finger over the outlet where its returning to the tank. That will force oil up to the rocker spindles and if you have the banjos loose you should see oil appear.

Careful tightening the banjos, don't let them turn and crimp the line.
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Re: BSA M33 oil ways

Postby Welsh Wizard » Thu Oct 18, 2012 10:45 pm

check you e-mail
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Re: BSA M33 oil ways

Postby Albertorondm » Mon Oct 22, 2012 2:07 pm

Thanks for all the advice and the email from WIZ. The amount of oil to the top end has improved slightley, wether its enough I'm still unsure but I'm going in the right direction. As the banjo bolts only have about 0.5mm hole (imperial????) and zero pressure its highly unlikely to be flowing at a rate of knotts. So for now I'll be happy to run it a little longer and work out my next move.

Thanks to you all
A
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Re: BSA M33 oil ways

Postby Welsh Wizard » Tue Oct 23, 2012 1:41 pm

20 thou seems a bit on the small size I would have expected a min of 125 thou.

however the rockers don't require a large amount of oil flow, as long as they are getting some, it should be good enough, after all it used to be up to the rider to push pull a pump in the older bikes before they had oil pumps .
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Re: BSA M33 oil ways

Postby Paul in NZ » Tue Aug 27, 2013 3:47 am

Also remember that as the oil gets hot and thins it will flow easier to the rockers...

Sorry I'm not sure if an M33 has a plain shell big end or a roller bearing but that makes a difference re pressure and flow requirements. I'm sure the system will have a p[ressure relief valve in there someplace too (lordy it HAS been a long time since playing with a pre unit beezer)
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