SRM oil pumps?

[Steverat]

I’m at the point in the rebuild where the pump can go back on. I think the old one is okay though it is a bit stiff to turn manually - just pushing the drive pinion around withe the ball of the thumb Is probably not significant torque.

Anyway, there is a lot of new stuff in the engine so I’m wondering whether a better oil pump would be a good idea. SRM have a strong reputation so I guess their pump is good- but is the benefit worth the significant outlay? Would I notice anything? How does the pressure and flow rate compare with a standard BSA pump?

Thanks for your data and thoughts....

[ellis]

No question about it SRM pump is the way to go. Bet you wouldn't like an old heart in your body.

ELLIS

[muskrat]

G'day Steve.
I can't help with a comparo but all that get one love it. I too would dearly love one too but can't justify 2 weeks wages. I refurb mine anytime I have the motor down. Just by lapping the marks out of the end plate and extension housing. Mark everything on disassembly so it all goes back in exactly as it was. tightening the screws little by little whist turning the worm. If right it will be firm to turn but no tight spots. Both mine are the original pumps and both can pump well over 80psi.
Cheers

[kiwipom]

hi guys, in my opinion putting an S.R.M. oil pump is insurance, you do all that work with new parts here and there so you dont want risk destroying everything by leaving the most important part to chance. I replaced mine as not being confidant of my own engineering to resurrect an old important part, but each to their own.
 Putting an oil pressure gauge in the system will let you know what is going on if you decide to keep the original pump, cheers   

[JulianS]

No comparison between a new SRM pump and an old mazac bodied one.

SRM miles better, larger feed and scavenge gears and body does not distort, I think most mazac pumps have distorted bodies with distorted oil chambers which is why they are stiff or lumpy to turn manually.

Mine been in use 9 years works fine does not wet sump. Well worth the money

[trevinoz]

Just a comment on the SRM pump as to whether it is effective in reducing or stopping wet sumping.
A friend recently restored a bike which was wet sumping.
He was advised to fit an SRM pump to the engine, which had been reconditioned, to stop the problem.
Pump fitted but the engine still wet sumps.
Obviously the check ball was not reseated during the overhaul but the point is an SRM pump will still pass oil, being a gear pump.

[Rex]

If the engine didn't have an oil pump then I would have fitted an SRM one, but I wouldn't spring for an SRM unit if the old pump was useable (even with work) which it was.
Given the use most old A rangers will ever have, and the inherent reliability of the pumps an old original pump is more than adequate.

[orabanda]

Over the last 30 years I have accumulated a few A10's.

I have had two of the original (Mazak) housings fail (crack and break away) in the thinner drive spindle area.

Others have shown signs of the metal crumbling away.

Not surprising that a 70 year old material,that was specified more for cost saving, than metallurgical quality (ie material was cheap), suffers fatigue failure.

I work in the fluid power industry; the only application of this material in a gear pump I have ever seen, is by now defunct manufacturers of British motorcycles.

All of my machines have a replacement high quality pump: some SRM, some cast iron).

Richard

[chaterlea25]

Hi All,
The old mazac pump bodies can also go porus
I have told the story before on similar threads about how a porus pump body wrecked my brothers SR
I also have seen so called rebuilt pumps fail to perform on SRM's test rig

(Just a happy New pump user)
John

[RichardL]

Over the last 30 years I have accumulated a few A10's.

A few? 

Richard L.

[scotty]

+1 SRM oil pump for me

Does not stop wet sumping in my case but I live with it

S

[beezermacc]

Just fitted a Wassell cast iron pump to my newly built bike. The flow rate looks the same as the previous standard pump but it has cured the wet sumping. The Wassell pump does not come with the crankshaft worm whereas the SRM pump does.

[chaterlea25]

Hi All,
Thinking back, some time ago, 2010 ??
I rebuilt a customer A10, I had the anti drain ball valve modded to seat against the rear of the pump when getting SRM to fit a new bush and grind the main and B/E journals
They rebuilt the standard pump at the same time
The bike wet sumped after the rebuild  so the owner asked me to fit a new SRM pump
That cured the wet sumping 

John

[beezermacc]

Hi All,
Thinking back, some time ago, 2010 ??
I rebuilt a customer A10, I had the anti drain ball valve modded to seat against the rear of the pump when getting SRM to fit a new bush and grind the main and B/E journals
They rebuilt the standard pump at the same time
The bike wet sumped after the rebuild  so the owner asked me to fit a new SRM pump
That cured the wet sumping 

John

A mate of mine bought a bike which had an SRM engine fitted. My mate asked me to have a look at it after it seized (twice actually). We stripped the top end and found no problems apart from seizure marks on the pistons so just rebuilt it again after cleaning the pistons up. However, on checking the oil return on startup I was alarmed to see virtually no oil returning to the tank. The bike had an original pump so I blamed that and we swapped it - no difference, still very little oil return. I'd noticed the ball and spring on the back of the pump and wondered if this was the cause of the problem so, off with the pump, remove ball and spring.... hey presto! A gusher of an oil return. I can only assume that the ball was compressing the spring completely thereby causing a blockage in the oilway. Whatever the diagnosis the modification had cut the oil off.

[chaterlea25]

Hi Beezermacc,
I cannot answer that ???
The ball needs to be 1/4in. it sits in a 5/16in. drilling ( I posted some photos on another thread recently of the setup)
If the wrong size ball was fitted it could cause a problem

I have my own SR with the SRM setup on it with in excess of 25k miles without issues
All the other A series bikes that I have rebuilt with the modification have run trouble free

John