The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Terryb on 13.06. 2020 17:04
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Can anyone tell me what size hole should be in the Banjo Bolt please? I've recently purchase a replacements from Dragonfly and they sent me a bolts with a 1/64" Hole, which seems a bit small. This is being fitted to a 1955 A7SS.
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Think that's about right, there are bolts with a noticeably bigger hole but they are wrong
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More than than 1/64" = too big!
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Think that's about right, there are bolts with a noticeably bigger hole but they are wrong.
The bottom banjo on 31's and 33's have bigger holes as it has to feed the two smaller higher ones, they get mixed up sometimes.
The modern ones S.R.M. now sell as rocker feeds also have bigger holes now. More oil down the pushrod tunnel and into the cam trough isn't a bad thing along with more oil splashing about in the rocker box. Downside is more of the same oil going around the engine.
What do others think on the subject?
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The B singles have 4 banjo bolts.
2 feed the rocker spindles from oil tank return like the twins.
The other 2 are drains from the rocker area of the head to crankcase via an external pipe. These banjos have larger holes.
The Goldie has an exhaust rocker spindle banjo bolt with larger hole than the inlet. These exhaust banjo bolts are sometimes fitted to the twins by owners.
The bolts supplied by Eddie Dow for his cast rocker feed had varying sized holes.
Not had any problems with differing sized holes over many years of use.
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Thanks for that useful info Julian and metalflake. I was told a few years ago by a BSA mechanic that the larger holed bolts were a definite no-no on twins.
Once I have sorted out my current engines smoking issue I'l try the orinal two bolts again and see if it makes any difference. Personally I would prefer a slightly increased oil flow to the rockers but I am certainly no designer on this engine so I tend to go with what the experts tell me.
Cheers.
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way back in the 80's when rebuilding mine I wrote to classic bike about opening up the two holes in the rocker box bolts. my idea being more oil down the push rod tunnel to cam and followers after seeing the state of mine in the engine when I took it apart. they said don't do it as the oil pressure relief should pump enough up to the cam trough. years later after my mistake of putting the oil lines on the wrong way round I was surprised how well all the valve gear had coped with no oil feed for many miles, the parts were inspected and the head put back on with no replaced parts . as classic bike said opening up the holes in the rocker feed bolts could cause more problems. when your engine is running and you slightly undo one of those bolts oil pours out, and look at the problems some people have stopping them leaking. they supply plenty of oil for the job without making them larger.
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Hi berger,
Yes, that would confirm my conversation with the BSA mechanic a few years ago.
He said very similar to you. He also quoted his experience of folks fitting incorrect Goldie bolts with much bigger oil holes in mistaken attempts to maximise rocker oil flow then causing over oiling problems.
Once I get my engine working as its suposed to I am going to try the old bolts just as a test to see what happens. Then I can pass on the results to all.
Cheers,
Dan.