40FW Fuel tank stud needed

[pdb]

Hi,

I am missing one of the two studs which are screwed in to the bottom of the fuel tank. The other ends pass through the two holes in the cylinder head to and fastens with a nut to secure the tank.

I am pretty sure the stud shaft is 5/16” I am not sure if it’s a BSW thread or not. I presume it is but I don’t know.

I would be surprised if it’s not a standard bit of British industrial hardware but I have no idea where to find one. Any help understanding the dimensions, thread standard, and sourcing clues would be greatly appreciated.

Thanks
Pete Brown
Anchorage, Alaska USA

[Charles uk]

Pete, shine a light inside the tank so you can see how your tank is constructed, the thread is 5/16 BSF.

There are several different tanks used on Seagulls it would help if we knew the model (serial number)?

[pdb]

Charles,

My engine is a 40 Featherweight 1977 GF1662AA Bing carb 25/1 prop SJM 1409

Pete

[Charles uk]

Pete look inside the tank at how that thread is fastened there, then you will understand the difficulties your facing!

[Horsley-Anarak]

I think it may be like this, silver soldered in during the manufacture of the tank.
Tank mount is also the little stub that sticks out of the back of the tank.

[Charles uk]

Thanks H-A a perfect picture! worth a thousand words.

[pdb]

My 40 Featherweight 1977 type GF engine has a different style tank than H-A’s photo shows. I do not have the reinforced hard points on the tank. The inside of the tank is bare except for the screen for the fuel tap.

The only means of attachment is by two studs that screw into two reinforced plates on the bottom of the tank. The studs pass through the two holes in the cylinder head and secured by nuts as you can see in my photo.

[Horsley-Anarak]

Steel tank, just weld on a 5/16" B.S.F. stud.

I would turn down the head of a bolt and mig weld it on , de-gas tank first.

[pdb]

H-A....I may end up doing that. I am going to explore the possibility of finding a double threaded 5/16 BSF 1.5” stud. That appears to be what Seagull put in these old steel tanks and I hope to keep it original. Failing that, welding a 5/16 BSF bolt may be my only hope.

I hope that it is not a BWS stud. I can’t find any BSF or BWS stock to compare.

I did get an email today from John at SOS who was pretty sure it was a metric steel stud. I dragged the tank down to a local supplier and have convinced myself that it’s not metric. The nut threads easily on the existing stud on the tank but only takes about 2 turns on a metric bolt before it jams.

BTW... are you any relation to Terence Horsley, the British writer, sportsman, and distinguished pilot from WWII?

[Horsley-Anarak]

[quote="pdb"

BTW... are you any relation to Terence Horsley, the British writer, sportsman, and distinguished pilot from WWII?[/quote]

No sorry no relation, I live in Horsley.
Thread is definitely 5/16" B.S.F.

[Donald A]

Sorry for gap in reply
John was right in my case - my steel tank on an early electronic featherweight was definitely metric - M8 I think - I was replacing the studs with stainless. I had to cut one end very short - slightly longer than the length of the female thread in the bottom extra plate on the tank, otherwise it bottomed out on the tank Inner bottom steel sheet, instead of the end of the male threaded stud
Unbelievable - and yet seagull were 10 years ahead of the Suzuki 2.2 in going to electronic ignition .......
Donald

[geofflena]

Yes - my DT2 is 1984 and is points still ! Great engine ( if I'm allowed to say so ! )

The one I bought had a stuffed water jacket ( tried to repair it to no real sucess ) Managed to find a used crancase/bore assembly - but that proved to have stuffed bore ! Luckily ( for £24 ! ) from french marine I got the last oversized piston and ring set in existance I think ( old stock )
So the outcome was I got myself a re-bored 2 stroke ! ( the best sort ) - for peanuts. Starts like a daisy.
If you go to somewhere like Brownes Point Marine ( they have all the parts fiches online ) and check parts no's - many of these old suzuki 2 stroke parts were co-opted from suzuki small 2 stroke motorcycle bits.
EU parts suppliers still currently list the coil. points condensor etc - and many of the carb parts - cheap too !
So can keep her going for a while yet.