petrol tank bolt

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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GOLDSTAR
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Re: petrol tank bolt

Post by GOLDSTAR »

I guess I now understand the reasoning, provided you have the correct length bolts and all the correct washers then they will not touch the tank bottom, not having all this information at hand at the time I improvised by the method I mentioned, certainly not wishing to be confrontational but I think like my method best for peace of mind :beer: kind regards
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Rob Harknett
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Re: petrol tank bolt

Post by Rob Harknett »

Thickness off rubbers, length of bolts are all in the parts list. They got a bit lazy in the latter years, so often you need to go back in time, sometimes even converting part numbers from new back to old. Then check the part in a pre 1951 parts list, if used then, you find even dimensions of parts are given. Don't go too far back through, you may find the sleeve missing. Makes you wonder why they introduced the sleeve? Yes, years ago you just nipped the bolts up and wired them on. Could it had been when the old bikers made way for the heavy handed mid 50's teenagers?
56G80S
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Re: petrol tank bolt

Post by 56G80S »

Hi All - I've revived this thread (!) as I thought I'd address the problem that I "bodged" before.

I don't have Andy51's resources but found these: https://www.mcmaster.com/metric-threade ... g-inserts/ . I got excited that I could overbore the existing tank thread holes, tap appropriately for the thick walled inserts, screw them in and bore out the inside thread (7mm drill?) and tap to 5/16" BSC. I have the taps. I thought absolute precision wouldn't be too problematic as there's plenty of wriggle room in the frame holes.

Then I realised the naughty word things are in the USA.

I might just see if I get someone (there's a local hydraulics engineer I know with a fully equipped workshop) to drill down an M12 set screw at 7mm. Then I drill and tap the tank for M12, screw in the hollow bolt with araldite or similar, cut of flush and tap to 5/16" BSC.

Johnny B

PS for the McMasters inserts I was looking at the 1/4" ones therefore the bore would be 6.25mm and running down the 7mm drill would, just about, remove the internal thread.
Yak
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Re: petrol tank bolt

Post by Yak »

Hi
I have had the mounting holes drilled out and brazed deep nuts in them flush with the plate. On my tank thereis still a 1 to 2mm gap between it and the nuts. Am not home at the minute but am pretty sure I am using 8mm bolt and nuts. If it helps I use a 13mm socket to do/undo them. Originally had them spot welded in but proved to be too brittle. The brazing has lasted some 25,000 kms. so far.
Ray.
56G80S
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Re: petrol tank bolt

Post by 56G80S »

Cheers Yak,

I (well a mate) did that with the previous tank and as you say, the weld broke off. I'm looking at a "non heat" approach but who knows.....................!

Johnny B
magnusk750
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Re: petrol tank bolt

Post by magnusk750 »

Experiences of Loctite on the tank bolts? No Lockwires chewing on the paint. Obviously the weakest of Loctite, as the tank must come loose for service from time to time.
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Group Leader
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Re: petrol tank bolt

Post by Group Leader »

magnusk750 wrote:Experiences of Loctite on the tank bolts? No Lockwires chewing on the paint.
Oh, I love a bit of wire locking and there's not much paint for the wire to chew on my Model 16. So much more satisfying than "glue" when it goes well and very annoying when it doesn't! The photograph is of course of an imposter but the principle is the same.

I do admit to running the wire through a tube on the AJs rear tank bolts as the wire does pass close to the rubber petrol pipe at one point and allowing it to chew through that might end in tears.

Alan
Wire Locking.jpg
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1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
56G80S
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Re: petrol tank bolt

Post by 56G80S »

Now looking at using M12 cup point grub screw, 1 cm long. They're hex drive and that will give a really good start for drilling through in order to tap at 5/16" BSC. I'll order 10 (about £5) so I have some spare for a practice on a piece of heavy scrap, No, I don't mean the Matchless. I'll probably cut the cup end off and create a flat blade screw slot for winding the grub screws in once drilled through. I don't fancy doing it once the grub screws are fitted.

If the practice works then it's a question of what to lock them in place with, araldite? What spec of Loctite?

I've found my "toy" Black & Decker drill press, which my old B&D drill goes into, so that should help with getting the drill through reasonable. Better than hand held.

Johnny B
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Re: petrol tank bolt

Post by Group Leader »

Aren't grub screws normally made from high tensile, very hard steel? Might make drilling and tapping very tricky!

As to Loctite grade - maybe 638? I've used 603 for quite a few things but I think that 638 is more permanent and you don't want your tank falling off!

https://simplybearings.co.uk/shop/p3402 ... _info.html

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
56G80S
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Re: petrol tank bolt

Post by 56G80S »

Cheers Alan,

The grub screws were advertised as "A2 stainless". IKBA about these matters. I'll find out when they come. I have finally bought some thread cutting oil.

Oh, well, it's only a fiver. They'll come in handy even if I never use them............

Johnny B
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