The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: BSA500 on 20.03. 2010 11:51

Title: Oil Leak what a surprise
Post by: BSA500 on 20.03. 2010 11:51
The bottom primary case screw-the large one of three that passes through the chaincase and screws into the crankcase-is leaking oil because the thread has gone.I know what repair is needed a helicoil but seeing as spring/summer is approaching and I rode through winter I am not stripping it down to fix it.Anyone got a quick 'bodge' to seal it off until I can strip it down(perhaps in a couple of years ;)).I have tried ptfe tape which has worked in the past not this time *sad2*.
Over to you.
Andy
Title: Re: Oil Leak what a surprise
Post by: RichardL on 20.03. 2010 12:57
Assuming you will fix the hole with a BSW 5/16-18 coil, you could try using an 8mm screw temporarily.  The 8mm screw will be just 0.025" bigger than the 5/16 screw. Maybe, hack-saw a length-wise slot through the 8mm threads to act sort of like a tap cutting edge. The drill in a BSW 5/16-18 coil kit is 8.3 mm, so this bodge should not bother your future repair. I don't guarantee this will work, but if it were my problem, I'd try it.

Richard L.


Title: Re: Oil Leak what a surprise
Post by: alanp on 20.03. 2010 15:51
Richard, here comes another bodge (I wish this was anonymous!). You can retap the thread in the crank case to fit an thread insert without pulling it completely apart, I've seen it done. Pull the primary cases off and retap the thread with the insert tap BUT turn the tap 1/4 turn at a time with the tap removed and cleaned each time and liberally re-coated in grease to collect the small bits of aluminium cut on each 1/4 turn.
I'm sure some will wince at this, but I saw it done and was surprised and convinced that provided you don't get too impatient and cut too much each time the small bits will come out with the grease.
Alan   
Title: Re: Oil Leak what a surprise
Post by: muskrat on 20.03. 2010 20:00
G'day Andy,
                Alan's got it, I've done it. The tang on the insert can be removed with long nose pliers.
Cheers
Title: Re: Oil Leak what a surprise
Post by: RichardL on 20.03. 2010 21:33
Andy,

Isn't it the idea that you don't want to pull the primary covers off right now, particularly the inner? Maybe I'm confused, but I don't think you can install the helicoil with the primary covers in place.

Richard L.
Title: Re: Oil Leak what a surprise
Post by: BSA500 on 21.03. 2010 10:32
Pulling the covers isn't the problem-expert can do that eyes closed with a hungry tiger breathing down my neck.In the past helicoils on the crancase have normally required the crank cases splitting.Seems that now that's not a problem.Finances are tight soon to lose the job sometime mid year so was after a ol leak stopper until that area of my life is secure the 8 mm screw is favourite at the moment.
ANDY
Title: Re: Oil Leak what a surprise
Post by: A10Boy on 22.03. 2010 19:28
Did I hear someone say Araldite ? No not me.

 *work*
Title: Re: Oil Leak what a surprise
Post by: BSA500 on 22.03. 2010 19:32
Bad man
Title: Re: Oil Leak what a surprise
Post by: BSA500 on 25.03. 2010 12:16
Had a bit of luck with this.The engineering storeman has turned up some old thread inserts(just enough for me sorry) which are self tapping and whitworth I think they are the Tappex ? brand anyone used these before.
Andy
Title: Re: Oil Leak what a surprise
Post by: muskrat on 25.03. 2010 19:04
g'day Andy,
                are those tappex like a hollow tap with a thread inside and out with flutes ? If so it would be the same as using a helicoil in that it would produce swarf when cutting it's own thread. They would also not have as much purchase of thread in the cases due to the flutes.
Cheers
Title: Re: Oil Leak what a surprise
Post by: BSA500 on 25.03. 2010 22:27
So lots of thick grease to catch the worst of the chippings,but most important they were free *smile*
Title: Re: Oil Leak what a surprise
Post by: muskrat on 26.03. 2010 06:23
OK, so when done remove the sump plate and inject copius quantities of petrol or alike through the said repaired hole to wash out any swarf that remains.
Cheers  *smile*