The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: RichardL on 15.08. 2008 23:33
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Rocker Feed Banjo Bolts
« Reply #38 on: 14.08. 2008 19:08 » Quote Modify Remove
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Quote from: dpaddock on 02.07. 2008 13:23
"dpaddock, do you know what size the feed holes in the standard banjo bolts are? ....Mike, the feed (radial) hole in the banjo screw is .046" (~3/64"). This is the orifice that determines the flow rate.
Gents,
The radial holes in my banjo bolts are different from each other. One is larger (for feed, I assume) and one is quite small (for venting, I assume). Does this sound correct and, if so, does it matter which one is forward and which is rear?
Richard
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From: manormike
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Richard
I recently found out that the feed holes are differently sized on Goldies. Larger for exhaust I believe because it runs so much hotter. So this could also be the case for twins? Is one smaller or larger than 3/64"?
Back to packing for the International, leaving 8 a.m. tomorrow, and the eather looks ok for once
Mike
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Sorry about showing up as three posts in a row, but I decided to make this subject its own topic and did it in an awkward way (rather than bothering Erling with it).
Responding to Mike, in looking through Bacon's "BSA Twin Resoration" book, I was surprised to learn that in early engines, up through XA7-450 in 1947, neither rocker spindle was directly oiled. Then, after said number, the exhaust spindle, only, was oiled, until 1949 when oiling of the inlet spindle was added. All this is very interesting, but I am still confused by the two different sized holes I have (in the banjo bolts, that is) and hope someone has an answer.
Richard
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The A7/A10 rocker banjo screws are identical inlet and exhaust (p/n 65-317), each having a 3/64" radial hole for oil feed to each spindle.
If you have different sized holes, the larger one's for a Gold Star exhaust spindle. It's usable for the A Group engine but might be an over-oiling problem and therefore you should stick with the original design.
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Dave,
Thanks, I'll order new ones. One more question, if you don't mind, could this issue have anything to do with the banjo being of the one-piece cast type by Weber? It would seem not, oil is oil.
Richard
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I lied. I did not order new banjo bolts. Too impatient and too cheap to spend around $22 (for two), parts and shipping. One of the holes was already 3/64", the other 3/32" Tapped out the latter with 3mm thread (total coincidence I had that tap and it fit the hole). Ground down a 3mm allen screw as a plug and drilled my own 3/64" hole. Total cost $3.25 and the banjo bolts are back on the bike. (My time and cost of gas to get to the hardware store 2 mi. away don't count. I am, after all, rebuilding an A10.)
Richard
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Good for you, Richard! I like your style.
David