The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: anjimehra on 27.02. 2014 08:34

Title: 1951 A7 oil retaining ball
Post by: anjimehra on 27.02. 2014 08:34

Hi

Lost the ball in the nrv in the timing side crankcase, the one supposed to prevent wet sumping & need to knowthesize
Thanks
Anji

Title: Re: 1951 A7 oil retaining ball
Post by: duTch on 27.02. 2014 08:46

 Hiya Anji,
      the new spare ones I have measure 0.2495,  *eek* close enough to 1/4"  I think some parts suppliers have the size posted on their lists
 Have to wonder how much difference a 6mm one would make, if any under duress.??
   Cheers

Title: Re: 1951 A7 oil retaining ball
Post by: anjimehra on 28.02. 2014 06:41

Hi duTch

Thanks. I think 1/4 should do fine especially with a light tap

Ride safe
Anji

Title: Re: 1951 A7 oil retaining ball
Post by: trevinoz on 28.02. 2014 21:43

Anji,
              You usually need a bit more than a "light tap".

Trev.

Title: Re: 1951 A7 oil retaining ball
Post by: duTch on 28.02. 2014 22:18

Sorry if it's obvious, but hold it in place with something and try and blow through the other way....?



 **To test it...**

Title: Re: 1951 A7 oil retaining ball
Post by: RichardL on 28.02. 2014 22:20

Hello,

I will be the LAST person to argue with Trev (since he always steers me straight, thank you), but I tried a different method. Specifically, using the old ball and some valve lapping compound to refinish the seat. I don't know yet if it worked, but I thought I had better try it having threatened to do so for some time.

In the first picture you see the ball epoxied on the end of a 1/4" aluminum tube. (this is the same tube I've used for timing, which is why it has the graticule with 1/32" increments). In the second picture, the tube is shown in my drill motor. I'm pretty sure the ball is smaller than 1/4" and I'll measure it later.

Richard L.

EDIT: 1/4" it is. Batting zero for February.

Title: Re: 1951 A7 oil retaining ball
Post by: trevinoz on 28.02. 2014 22:38

The last one that I did I just gave it a light tap then assembled the ball etc. I then put oil into the port and waited. It seeped through.
So I pulled it apart and used another ball and gave it a good whack. Put it together again and tried it.
I left it over night and the oil had not dropped.
Hopefully it will hold against the head of oil when I get around to building the rest of the bike.
Trev.

Title: Re: 1951 A7 oil retaining ball
Post by: RichardL on 01.02. 2020 21:53

Not '51' but on the topic of "Oil Retaining Ball."

Working on my '57 A7 eBay barn find. As appears to be usual, the retaining ball grub screw was completely resistant to removal. As I did on my A10, I drilled it out and set about trying to remove it with an easy-out. No go, until heat was applied. The remaining thread looked sketchy and was quite loose when tested with a 5/16" Whitworth stud. I think I expanded the diameter in the first easy-out attempts. Not that it's a big deal, but fixed it with a helicoil, as shown in the photos. Used a flood of blue Loctite, wih the expectation it will also serve as thread seal.   I plan to make a new grub screw from a bit of cut-off stud.

Richard L.

Title: Re: 1951 A7 oil retaining ball
Post by: RichardL on 01.02. 2020 22:12

Adding to this, Richard (Orabanda) is a mentor to me, even if it's not voluntary on his part. I plan to follow his guidance for spring and grub screw shown in this post: https://www.a7a10.net/forum/index.php?topic=13293.msg112118#msg112118 .

One question, if anyone chooses to opine. Am I correct in the assumption that the ball is never pushed from its seat as far in as the oilway to the main bearing? This, then, means oil just flows around the ball to get to the oilway, correct?

Richard L.