Leak back,

Here you can talk about all kind of TECH for the B50 B44 B25 And Other BSA unit Singles

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Johnq1
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Leak back,

Post by Johnq1 »

My b25 project has been stood a couple of months and yesterday was the Big first start day, anyway after the usual double checks of the timing and fuel I found it difficult to kick, on dropping the sump plate I got approx a litre of oil out, topped up again and the rest went well just fine timing and carb (pwk) set up after lockdown , my question is what is the normal amount and will this problem improve/go away when the bike is used more, TIA cheers John
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kommando
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Re: Leak back,

Post by kommando »

Normal, its called wet sumping, the more you ride the bike the less of an issue. When these bikes were daily riders the problem never came up.
Jeff K
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Re: Leak back,

Post by Jeff K »

Nice Bike! What gas tank are you using?
Jeff
Johnq1
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Re: Leak back,

Post by Johnq1 »

Tank is by Holtworks in the UK
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petergj
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Re: Leak back,

Post by petergj »

A very nice bike. Kommando has explained the leak back characteristic.

I am restoring a B50 powered Cheney and am interested in your silencer. Can you advise who made the silencer?

Thanks and regards,
Barry Creary
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Re: Leak back,

Post by Barry Creary »

Hi John I had the same problem with my B50 getting about 100mm overnight I tried all the usual fixers still the same I think komando advisedly check the oil pump shaft for wear the oil was escaping down the shaft and wet sumping I had the pump bushed and was fixed
beesa71
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Re: Leak back,

Post by beesa71 »

If John will excuse me; here’s a link re’ the exhaust system.

http://b50.org/phpBB2/viewtopic.php?f=2 ... ons#p64189

Regards.

Paul.
Johnq1
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Re: Leak back,

Post by Johnq1 »

The exhaust system was sand bent by Ben at Raysons exhausts (It's loud) pic made McN when Raysons were featured a while back
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Johnq1
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Re: Leak back,

Post by Johnq1 »

beesa71 wrote: Tue Apr 21, 2020 8:35 am If John will excuse me; here’s a link re’ the exhaust system.

http://b50.org/phpBB2/viewtopic.php?f=2 ... ons#p64189

Regards.

Paul.
no problem All help appreciated
Johnq1
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Re: Leak back,

Post by Johnq1 »

I would recommend zooming this picture to look at the jobs list on the blackboard, very special
FranktheWelder
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Re: Leak back,

Post by FranktheWelder »

Johnq1 wrote: Wed Apr 22, 2020 10:13 am I would recommend zooming this picture to look at the jobs list on the blackboard, very special
The whole image is filled with amazing.

By the way, your bike is stunning!!
machines, materials and motorcycles.
Johnq1
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Re: Leak back,

Post by Johnq1 »

Couple more pics for frank
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FGF
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Re: Leak back,

Post by FGF »

Hello John ,

i 've the same problem of wet sump on my B50SS.
i 've read many posts.
The first solution is to put a stronger spring in the feed non return valve . Does it works ?

Second solution : the oil pump
there is a tip on the home page and Barry ( Creary ) said to put bushes in the oil pump case too.
VOXAN oil pump
VOXAN oil pump
no oil seal OK, just Bushes with a good gap !

wet_sump2.jpg
BSA bushes above

So has someone the blue prints of BSA oil pump to make a good work fitting bushes in the oil pump case ?
what is the center distance ( D note ) between the two shafts and its precision ? what are the precision on the shaft diameters and the gaps ?

Third solution : some supplier sell a new two studs pump , SRM . It could be better than an old three studs one ?

However, your bike is very nice John.
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kommando
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Re: Leak back,

Post by kommando »

I do this, the pic is of a Norton pump but it works on all Unit Single pumps. I had seen it done by AMR as part of their Norton mods but with O rings but I thought X rings would double the chances of a seal.

Image
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FGF
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Re: Leak back,

Post by FGF »

thanks Kommando ,

usually , the oil pump don't like oil seals because a little leak oil the gears and bushes. ( like Voxan picture )
with such an oil seal , the bottom gear risk to work dry .

the problem is to work with the good gaps and precision ...
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crankbuster
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Re: Leak back,

Post by crankbuster »

Here are the BSA pump dimensions
OILpUMP.jpg
I don't have the tolerances for the .375 but you can see that the extra length means it does not need to be so close
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FGF
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Re: Leak back,

Post by FGF »

Wonderful Crankbuster ,

the three studs oil pump must have doubtless the same precision .
this will be very useful to check one's oilpump wear and decide to machine it.

still many thanks.
Johnq1
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Re: Leak back,

Post by Johnq1 »

Not being an engineer, who makes or repairs pumps for these as srm don't do one for my bike, or do I just live with it and drop the oil after trips??
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FGF
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Re: Leak back,

Post by FGF »

Hello John ,

Have you tried to change the non return valve spring ?

After ,if it doesn't work , in England you will find some fitter-ajuster who can machine your pump.
a bike specialist would be better .

Good luck.
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kommando
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Re: Leak back,

Post by kommando »

My b25 project has been stood a couple of months and yesterday was the Big first start day, anyway after the usual double checks of the timing and fuel I found it difficult to kick, on dropping the sump plate I got approx a litre of oil
1 litre in a couple of months is nothing to worry about.

I did something on my Norton only when the oil tank emptied in 2 weeks.

Rebuilt pump, added non return in cover ala BSA. No more wet sumping.
Mr Mike
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Re: Leak back,

Post by Mr Mike »

Mine drains down in a few months and I just start it up and idle the bike till it is back up on the dipstick before taking off I never drain it out and pour it back. The fix is ride at least weekly.

Mr Mike
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