BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: RICHARD MILLS on 25 May, 2017, 14:08:25

Title: B33 petrol tank
Post by: RICHARD MILLS on 25 May, 2017, 14:08:25
I have a stripped thread on the stud on one side of the tank where it holds the 'petrol tank stiffening plate' (42-8058). I didn't do it - honestly! Can anyone please tell me if the studs are screwed in or welded in? They do not look as though they will unscrew and I don't therefore want to wrench them. I suspect they are fixed because they are not shown separately in the parts list.
If they will not unscrew I have considered the following possible solutions, either:
1. Try to cut a new thread in the faulty side. (Metric alert - jump to 2 if you are likely to be offended!) Best thread would seem to be an unusual but easy to obtain M7x1.0. Or,
2. Cut both studs off and weld on the heads of 5/16" set screws of an appropriate length. Don't fancy welding on a petrol tank, but have emptied it and it is airing in the sunshine. This is my preferred option, but any other ideas would be appreciated.
Title: Re: B33 petrol tank
Post by: RICHARD MILLS on 25 May, 2017, 14:16:55
PS I realize that I could drill and tap the pillars, but they are only short and narrow and therefore I don't think that it would be a good option.
Title: Re: B33 petrol tank
Post by: JulianS on 25 May, 2017, 14:29:49
Unfortunately they do not unscrew.

Could you run a 5/16 x 26 tpi dienut down the thread or is it too bad?

It is quite difficult to run a split die in a die stock down the thread because there is not enough clearance for the arms of the stock due to position of the other stud.

You need to be careful not to use to much force because the base of tank is quite thin.
Title: Re: B33 petrol tank
Post by: RICHARD MILLS on 26 May, 2017, 13:02:18
Thanks Julian. Thread is beyond repair.
Looks like the welding option is the one to go for.
Title: Re: B33 petrol tank
Post by: DEAN SOUTHALL on 26 May, 2017, 15:12:14
Do you mean the fastenings at the the front underside that attach the anti-vibration plate. If so, you could try cutting and drilling the stud and epoxying a replacement stud in there. If its doesn't work then not much lost.
Title: Re: B33 petrol tank
Post by: RICHARD MILLS on 27 May, 2017, 17:40:24
Thanks Dean, but I don't think there is much scope for a firm epoxy fitting.
Advantage of the welding solution is that I could leave two opposing flats on the setscrew heads without weld. This would mean that I could hold with a thin spanner when tightening the fixing nuts, therefore removing any stress from the base of the tank.
Title: Re: B33 petrol tank
Post by: paulm on 03 June, 2017, 09:06:39
Hi be very careful welding espicially with Mig or Stick, I gas weld or braze main reason being i can flash the tank first so i am in control also as it is so thin i prefer gas, Secondly a lot of people run with out these its your choice, but unfortionatley i am anti metric so i would cut off and fit the correct thread.
One of my main hates with wrong threads is trying to work on them, i have been to rallies all over europe and you often see people struggling becaise they have brought the wrong tools, with the correct threads and nuts everything you need will fit in your tool box plus more, I have done head gaskets in fields in Belgium with the contents of my tool box
Title: Re: B33 petrol tank
Post by: STAR TWIN on 03 June, 2017, 10:27:55
It was often said that you should do all your maintenance with the tools in your bike toolkit. Very true. Fitted a new tube to the front wheel of my Star Twin yesterday and discovered that the bike toolkit was lacking a tommy bar. These things are best noticed in the comfort of your shed rather than in the middle of nowhere.
Title: Re: B33 petrol tank
Post by: RICHARD MILLS on 03 June, 2017, 18:26:26
Thanks to everyone for their comments and advice.
Successfully MIG welded today! Welded onto the pillars so no problem with welding onto thin metal.