The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: townsends20 on 15.07. 2011 10:27

Title: srm prv.
Post by: townsends20 on 15.07. 2011 10:27
Can someone tell me if fitting a SRM prv ( a7 type ) to my rgs will give me problems I have fitted one on this rebuild  but have not run it yet, it was tight to go in and I have been told that it will jam if I don't re-tap the thread to relive the pressure on the valve is this so or will I be better of just putting the old one back.
   Steve.     ???? :!
Title: Re: srm prv.
Post by: MG on 15.07. 2011 11:44
Hmm, how tight is tight?
I don't think it could compress the housing enough to trap the plunger (I assume the SRM valve has a plunger fitted?). You could take the end cap (acorn nut) off, and with the valve in situ in the crankcase, check whether the plunger still moves freely. If it does, it should work okay.

Cheers, Markus
Title: Re: srm prv.
Post by: Brian on 15.07. 2011 12:22
There was a thread about these SRM ones some time back and I actually managed to find it.

http://www.a7a10.net/forum/index.php/topic,1861.0.html
Title: Re: srm prv.
Post by: A10Boy on 18.07. 2011 10:18
As an update on that thread, I re-fitted the old ball PRV and have had no problems. I bought a tap to run down the threads next time the cases are apart so I can fit the new one.

Cheers
Title: Re: srm prv.
Post by: townsends20 on 20.07. 2011 16:45
yes i think thats what i will do. i did ring srm they told me that it could stick the plunger if it is to tight going in and they would send me out a tap to re-thread if i wanted, i told them it was all built and i did not want the bits in the oilways, he said that if the main bearing was still on the bush and has not been modifed it would blow out with the airline! i don't think i want to take that chance, so i think i will take the dome nut off and check the plunger and spring and go from there ( i will probably put the old one back just for piece of mind) what would you do?
  steve :! *dunno*
Title: Re: srm prv.
Post by: MG on 20.07. 2011 18:53
SRM also sell new springs and balls for the BSA valves.
I think that is what I would go for, if in doubt about the SRM valve working properly: Fit a new ball, give it a light tap so that it seats in the housing, and replace the old, potentially tired, spring.
Title: Re: srm prv.
Post by: A10Boy on 05.08. 2011 19:08
Quote
he said that if the main bearing was still on the bush and has not been modifed it would blow out with the airline!

It wont if the oil hole in the case lines up with the oil groove in the crank journal, it will blow the shite in!

Title: Re: srm prv.
Post by: wardleybob on 30.10. 2012 13:06
srm used to lend you a tap free of gharge
Title: Re: srm prv.
Post by: RichardL on 30.10. 2012 13:33
First, I'll go on record that this is not a recommendation, but just some thoughts.

Say you chase the prv thread, the bits are most likely to be quite small and trapped in the flutes of the tap. Also, they are aluminum, not steel. Now say you fashion small diameter tubing to the end of your vacuum-cleaner hose and vacuum out the hole. There will be strong suction indeed at the end of that tube. It would seem that the only bits that would avoid cleanout would be on the very small particle level. No, I would not like those drifting around in my engine, but it seems to me (this is where I will be slapped by people I respect, so I won't take offense) that these aluminum particles will not damage or plug the innards, but will soon sit atop the sump filter screen or be trapped in an external filter, if any. Finally, perhaps the tap is a fluteless thread chaser, ipso facto, no particles.