Square 4 MK II petrol tank fitment

[pauldridge]

Yesterday I received an all chrome tank I ordered for my '53 MK II, with reservation, from India, with the idea of doing my own painting/pin striping (my tank is currently serviceable, but only after plugging up some 5-6 pin holes). The tank was advertised on eBay specifically for the MK II Ariel.

I took the tank out to the shop today for a trial fit.. was I surprised.. the mounting threads on the tank are a good 3" further apart (fore/aft) than the lugs on my frame. My frame lugs, front to rear.. are about 13" on center, whereby the tank's bosses are 16"! Not too happy with the quality either.. a few imperfections in the chrome, as well as small goobers in the metal body. Worse.. they had slopped some sort of red coating inside, which was already coming off in big flakes.. about a 1/2 cup fell out the tank opening, so that is going back to Delhi. It is also questionable if the threaded bars on the tank are the same pitch as the original bolts. I tried those, as well as standard 1/4" course and fine thread SAE bolts, and found nothing that would screw into the threaded piece without a lot of undue persuasion.

My Sq 4 is a 1953 (MK II).. just wonder if all the frames have the same mounting lug spacing, or somehow the '53 was different (I'm guessing these guys just slap these things together willy-nilly, but want to confirm that the standard MK II frame has mounting lugs roughly 13" front to rear)

Once again, I am learning you get what you pay for!

[paul.jameson]

You learn something every day about Ariels ! I have just been into the shed to check. Rigid and plunger tanks have 13" approx centres. This includes my 1936 4G, 1937 RH500 and 1953 KHA. The swinging arm bikes seem to be about 15 3/8" centres. But my 1957 onwards Square Four tank is 16" centres. This must be a change from the 13" norm to accommodate the modification to the Square Four frame from 1954-on for the SU carb. Oh, and my swinging arm Square Four frame has centres about 17" so I shall need to sort that problem when (and if) I get round to building the bike with the 16" centres tank.

[Ken Harrison]

Re:Squar 4 MK11 petrol tank fitment. Actual measurments off my old original 1955 4GMk11 Tank.
Front tank hole centers across frame are 6" (Thats from right to left of frame)
Rear tank hole centers across frame ( aft of petrol taps ) 4-15/16"
Front of tank to rear of tank hole centers 16"
All tank welded on under straps are tapped 5/16" Whitworth.
I puchased a new Indian tank from Draganfly and had it chromium plated and painted and lined in the UK When I came to fit it I found it to be approx 3/16" out on the hole centers across the frame and about 1/8" out on the front to rear hole centers.So as the frame lugs are well proportioned I thought I would open them out with a 9/16" HSS drill which would give me enough tolerance to take the new tank mounting bolts.!!!!
THINK AGAIN THEY CHILLED STEEL CASTINGS !!! Result a few wrecked drills and round files were usless to so eventualy resorted to a few hours with a high speed Dremel Flexible Drill with small dia grindstones (Quite a few) of those to. But am very pleased with outcome. But I think even Draganfly have reservations on these tanks.But still not an easey tank to fit with the correct rubber buffers in situ.
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Ken Harrison 55 4G, 59 BSA DBD 34 Clubmans Trim . 1947 Scott Flying Squirell (Special Moss High Performance eng) Project.Kawasaki 1980 100cc

[pauldridge]

Thanks Ken,
Because of expensive shipping costs US-India ($100 USD or so), the seller eventually agreed to let me keep the tank for just $50 total (he reimbursed the remaining cost, including original shipping). My frame (1953) definitely has only 13" front-to-rear centered lugs, but I figure easy enough to just weld some new tabs underneath in the correct position. I will be painting the underneath the standard black color anyway, so no worry about discoloring the chrome underneath. I may very well tap the new holes as standard SAE threads, since Whitworth taps and hardware are hard to come by here in the states.. that way I can insure I have the exact correct length of bolt to not drive it through the tank bottom.

This tank is fully chrome plated, so I am going to have to find a way to mask the correct chrome areas, then bead blast the remaining tank to allow paint to stick.

After my original posting, I tried out my new petrol cap (from Draganfly) and found the hole in the tank to be slightly out of round, to the extent the cap will just barely fit, after a bit of fiddling every time. The workmanship on these Indian tanks (at least this one) is crude at best. I can almost envision some worker sitting barefoot in the dirt beating this tank into shape with a spoon!

Who knows? I guess it is possible that my frame is somehow from a Mark I, but with the MK II engine? Given the state of my bike from P.O., I wouldn't put anything past him.

My frame (or VIN number) is ES694 The engine, near as I can tell, is XJ536..

I would appreciate any comments from other owners as to the tank mount lug measurements specifically on a 1953 MK II, as well as if these numbers jive with that model year.

[Brian.Fosh]

Hi,

The indian tanks on ebay are no doubt useful if you are are prepared, willing and able to undertake some panel beating or fitting work. After all, my original tank just cost £480 to get chromed, but chromed patterns on ebay sell at £150.

I find the volume of tanks on ebay dominate search results for ariel parts.

If you are not aware, you can exclude words on ebay searches by prefixing words with a minus sign, no space..

so for searches here in the UK, not including descriptions, within the category of Motorcycle parts..

"square four" ...............370 hits
"square four -tank" ........82 hits (wow!)
likewise
"sq4".....................92 hits
"sq4 -tank"..............23 hits


Brian.

[paul.jameson]

Phil,

Stop worrying. Your engine and frame numbers match the factory records.

Paul

[david.anderson]

Paul
If the tank is already chromed it can be welded satisfactorily. But it must be welded with a TIG welder using stainless filler rods. The stainless rods mix with the chrome and the final result is that no one would know. I have seen several broken chromed muffler brackets repaired in that manner. There is never any rust and a good neat tig weld is virtually unseen.
The one place you may have a problem is that there is an indent in the petrol tank above the fixing bolt. I had to move the fixing bars on an Indian tank that I purchased. I used an oxy torch to cherry the tank and push an indent in the new location above where the fixing bolt would fit.
There is no need to bead blast chrome to get paint to stick. There are etch primers that adhere very well to chrome. Phone a paint manufacturer for advice on which primer to use. I use Protec vinyl etch primer grey which is available locally here and adheres very well to chrome.
David

[pauldridge]

Thanks for that advice David , on all counts. I did plan on using my TIG, vs MIG, if for no other reason to avoid splatter onto the "good" part of the tank, but I hadn't considered the need to use stainless rods.. you probably saved me a lot of grief! I didn't see an indent underneath in my tank. Instead, it seems they bent the mounting strip before welding, to give some clearance for the bolt, but the indent makes lots of sense. Should I have any worry about the torch heat affecting the chrome on the outer side of the tank?

[david.anderson]

Phil
Sorry that I got your name wrong.
I brought my tank to cherry red and pushed the indent, but I was not working with a chromed tank. That heat is not going to be kind to the chrome. If your tank is set up with bent bars then I would use the bent bars and forget the indent.
The heat from the tig is so localised that it will not affect the chrome.
David

[simon.holyfield]

I think that I have fallen into the 'Paul' trap a couple of times!

Sorry Phil!