Rebuilt bottom end - oil pressure ?

[nigeldtr]

Well, fired her up for the first time on the 31st Dec 2010 (was about -5C outside) and took her out for the first time in the sun today +8C, lovely day but still a bit cold. Anyway, she is running a treat with the new bottom end. Soon after I bought the A10 I discovered the oil pressure was low (engine very noisy when hot) reason - timing side main was shot and also cam and followers, probably due to the lack of oil ? lucky she didn?t drop a rod on me! Sold in good working order ha ha! On start up, cold, almost pops my pressure gauge - goes to about 90 -100 PSI.  I took her out or a spin for about half an hour and the running pressure at 55 mph when warm settled to around 40 ? 45 PSI. tick over drops down to 15 to 20. I have a new SRM oil pump and pressure relief valve. I assume the pressure relief valve is open at normal running speed and allowing oil to the cam ? not sure though as I can?t really see from the gauge when the relief valve opens? Oil is 20-50 multigrade at the moment and will probably swap to straight 50 in the summer. The pressure gauge take off is just before the relief valve.

PS clutch is very heavy ? new plates and springs fitted, I think I need to back off the screws a bit ? any experiences?

[MG]

Hello Nigel,

good news, congratulations! The oil pressure figures sound absolutely fine to me. If the pressure stays constant at a certain level with rising rpm, I would think the release valve must be working. But you are right, there is no way to actually see if it does. Guess the only way is to take it out and test it with compressed air or something.
SRM offer Triumph valves with a pop-out indicator, maybe something like that could be fitted to the BSA valve as well?

I set the clutch up so that it is easy and comfortable to operate for me. If it slips, then I know that I have been too lazy and need to make it a bit tighter 

Cheers, Markus

[nigeldtr]

Hello Markus,

Thanks for the crank! ? It?s in there and running fine. In the end, I turned the new main bearing to just fit the journal and then pushed it into the housing, fitted the crank, with no rods on, bolted the halves together and span it up by hand, took off the high spots  with fine wet and dry and then left it in the lathe for about an hour on low revs, regularly squirting in some oil - not line boring but the best I could do 

Kind regards

Nigel

[chaterlea25]

HI Nigel,
I would think 90 -100psi is too high ??
To the best of my knowledge the PRV should open at 65-70psi, higher pressure could damage the oilpump drive gears
Maybe the PRV was sticking at first??
I would contact SRM and ask the questions??

HTH
John O R

[Goldy]

I dont know the correct way to adjust the clutch springs. I tighten the nuts until they are flush with the stud. The lever is then easy to operate. I then increase the turns on the nuts one at a time until it stops slipping but is still easy to opertae. A bit trial and error but it seems to work.

[nigeldtr]

Hello Goldy,
 I should have given the clutch a quick road test without putting all the covers on - now I'll have to take them (plunger A10) off again and drain the oil - shame nice and oil tight. Just used grease on the gaskest so should come off easily.

John, re the oil pressure it seems to be very high from cold simply due to the viscosity (today it was 8C outside) which falls rapidly once the oil gets hot. I think the flow resistance through all the oil ways to the cam simply means it?s high across the relief valve when cold? Once hot,after about 15 mins running, it drops down to around about 40 PSI. I suspect the valve is not the pop type but sort of slides open as the pressure increases. If it only opens at 60 PSI, then with normal running, the cam will get no oil? Not sure if I can solve this little mystery. With my knackered main, the oil pressure started also at around 60 to 80 PSI but fell rapidly to about 8 PSI once the engine got hot. I might swap back to the old valve and see if I can see any difference in operation. Would be nice to know what is happening in the cam oil way!

[MG]

Great to hear "my" crank got a good new home in your engine  

The release valve definitely will onyl slide open, since it is simply a ball (or plunger with the SRM type) and spring. If it is closed at low rpm, the cam has to live with the oil it has stored in the trough and with what comes back down from the inlet rocker arms.

[chaterlea25]

HI Nigel,
To my mind the PRV is there to "regulate" the pressure,  liquids do not behave the same as air or gasses under pressure
once the PRV opens, pressure reduces, So the pressure should not rise above the opening pressure to any extent
Your new SRM prv is of the plunger type, I have heard of people having to put a shim under the cap to reduce the pressure!!!
One question? was the prv very tight on the threads when you were fitting it? sometimes they are and I had a thought if the prv was very tight screwing it in it may distort and bind in operation ?????
If the prv is "stuck" partially open you will have very high oil pressure when cold and low when hot
If the oil pressure is 40 lb sq in when hot there is not much oil going to the cam?? (unless the prv is partially open)

Anyway thats my 2 cent opinion, twil cost little to phone SRM!!

HTH
JOHn O R

[A10Boy]

I'm fairly certain that the cam only gets oil from the pump at start up when the engine is cold and pressure is high, once the oil warms up and pressure reduces [and the PRV closes], the only oil the camshaft gets is what is in the trough and what gets flung off the big ends. While marginal, it is obviously sufficient.

As for setting up the clutch, assemble it with the nuts level with the threads as a starting point, but the main thing is to ensure that the plate lifts squarely or it will drag and crunch the box. So before you fit the primary chain, fit the cable etc and try the lever, you will see visually if it lifts square or not, if it doesn't adjust the nuts till it does then assemble and test ride. If it slips, turn the nuts in a coule of threads - making sure its still lifting squarely and test again.

I fitted an SRM pressure plate and springs, it's now as light as a japanese clutch.

[nigeldtr]

Thanks for the thoughts and advice. I am also of the opinion that the cam only gets a good feeding when cold ? might be wrong, and lives of what is thrown at it or runs down from the valves when the engine is hot. The new PRV was a nice fit and screwed in by hand and then just nipped up. I will pop the ?standard? one back in for a test to see how it behaves. Nothing like a little mystery to keep the interest going ? have to be careful what I say now 

Re the clutch, I?ll trying backing the screws off and see how I get on ? I have a plunger so a bit difficult to get the chain off (continuous) with the clutch on, if you see what I mean.

[BSA_54A10]

First, the oil pressure sounds quite fine to me.
The cold pressure is insignificant to a large extent and is very dependant upon things like temperatures.

As for the clutch.
Adjust the springs to get a square lift.
Put the bike against some thing solid like a brick wall.
Engage 4th gear and try the kick starter, it should not slip.
Now back off each nut 1/4 turn and try the kick starter again.
Continue till the clutch just slips then retighten 1/2 turn.
Confirm settings by starting the bike, engage 1st gear and let the clutch out.
If it loads the engine and it fells like it will stall then you are there

[iansoady]

As for the clutch.
Adjust the springs to get a square lift.
Put the bike against some thing solid like a brick wall.
Engage 4th gear and try the kick starter, it should not slip.
Now back off each nut 1/4 turn and try the kick starter again.
Continue till the clutch just slips then retighten 1/2 turn.
Confirm settings by starting the bike, engage 1st gear and let the clutch out.
If it loads the engine and it fells like it will stall then you are there

Sounds reminiscent of the Velo drill, which I was never altogether sure I had right, but should be effective.

[BSA_54A10]

The book method gives a clutch hat is guaranteed to work regardless.
This is to protect BSA from law suits when a 22 St rider with his 14 St girlfriend on the back lets the clutch out as he changes gears trying to beat the express train across the level crossing.
RSI had not been invented by the nanny lawers yet so straining the wrist was not a legal problem.

[iansoady]

Put the bike against some thing solid like a brick wall.
Engage 4th gear and try the kick starter, it should not slip.

Actually, having thought this through, the drive to the back wheel isn't going through the clutch but is internal to the gearbox, so this wouldn't work. Unless the BSA gearbox works differently to the Norton boxes I'm used to.....

[lawnmowerman]

This has turned my understanding of oil completely on its head. I thought that oil viscosity (thickness) was measured by the time it took a fixed amount to pour through a standard sized hole - the longer it took the higher the viscosity - the lower figure on the multirade being the cold measurement and the higher being the hot measurement. 10W (winter) /50W being a good oil for winter use to stop the oil turning to treacle when cold.
I thought that the idea of a multigrade was that when the oil was cold it was thinner to allow quick circulation on start up and as the engine temperature increased and bearing tolerances widened, the oil thickened up to the higher range to fill the space in the bearings and maintain oil pressure.
It seems from the previous answers that the opposite happens.
Now I'm totally confused. 

Jim