The BSA A7-A10 Forum

Technical => Frame => Topic started by: brissy_bsa on 20.04. 2010 06:25

Title: 51 Plunger Tank Strap and other questions.
Post by: brissy_bsa on 20.04. 2010 06:25
I have a 51 A10 Plunger and have noticed to protruding luggs/bolts underneath the tank (front end). They tell me I need to place a strap between the two ( just a strip of steel to brace it). Is there are part number for that? Is that what the luggs are for?

Secondly, Can anyone tell me what the part numbers are for:

1. The washers for the oil feeder pipe rocket cover end and also the bolts.

Hope someone can be of help.

Ian
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Josh Cox on 20.04. 2010 06:38
washer 15-203
bolt 65-306

You can make the strap out of steel, apparently it stops the centre of the tank from cracking.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: gold33 on 20.04. 2010 08:00
Always wondered why they were there.

Is the strap necessary? were they chrome or the colour of the frame?
I don't know if I have a strap fitted or not but I think I would have noticed if I did.

Darren
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: brissy_bsa on 20.04. 2010 08:53
Thanks josh. um Darren, i have no idea, but if it stops the tank from splitting, well I will just make a strap and bolt it in, better safe than sorry. ian
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Josh Cox on 20.04. 2010 10:09
Painted apparently.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: MikeN on 20.04. 2010 12:23
I would definately fit the strap . Its to tie the 2 sides of the saddle tank together and stop fracturing from vibration. lots of makes of bike have them . Ive repaired a couple of (Velocette) tanks that have split on the saddle at the front end through ommitting this part.
Mike
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Brian on 20.04. 2010 12:40
And again, definitely fit the strap.

For the owners of central bolted type tanks, eg,swingarm models this is extremely important, do not ride your bike unless this strap is fitted or else the tank will eventually crack around the central hole, not might, will.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: RichardL on 20.04. 2010 12:53
I'm glad this topic has come up. I have a 2-1/2 gallon tank on my S/A frame and the strap passes through the lower hole of the dangle-down rubber bumper holder. Is that typical? I made my strap from a left-over tubular front mudguard stay. The way it fits through the dangle-down (hold your jokes), I doubt if a flat strap would have worked.

Richard L.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: muskrat on 20.04. 2010 13:02
A friend omitted his strap on a trihard just to test ride around the block. Tank split, trihard burned.
Cheers
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: brissy_bsa on 21.04. 2010 01:20
Wow, Glad I brought this up. Um, does anyone have the correct part number? ian
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: gold33 on 21.04. 2010 01:33
Glad I saw this post!

Does anybody have a picture of a correct strap? are they flat bar or shaped to tension the seam at the bottom of the tank?
When I bought the bike it came with 5-6 powder coated strips of metal that I assumed were all different types of seat mounting plates.

After all the drama of the last 7 mths I'd hate to have the tank split...
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Brian on 21.04. 2010 07:50
Just a flat piece of bar. You can make one out of any lump of metal you have lying around.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: a10gf on 21.04. 2010 09:59
^^^ agree, just measure up the distance, and drill 2 holes. Was missing on my bike too (when bought it some 15 years ago), then read somewhere about tank split and quickly dug up some leftover metal strip and secured it.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: beezalex on 21.04. 2010 17:35
Plunger A10 Tank stiffening plate: 67-8085
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: RichardL on 21.04. 2010 17:38
Here are a couple of pictures of my approach. I am still curious if running the strap through the bumper holder is the correct or usual path. Does anyone know? In my case, the landings for the strap occur fairly high up with respect to the hole that the strap passes through. Therefore, the tubular strap works just right in avoiding the curvature of the through hole.

Richard L.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: LJ. on 21.04. 2010 17:59
I also took some photos of the underside of the petrol tank... seems Richard has beaten me to this again! Richard you'll notice on mine that there are two rubber bungs, either side, in the holes where your support bar goes, they help to stabilise the tank, but would be no good for the smaller American market tank. I just still don't know why you guys have a smaller tank??
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: gold33 on 22.04. 2010 01:15
Now I confused!
I don't have the isolating block coming down off my frame, is this a feature of later swing arms perhaps?
It is not in the diagrams in my parts manual either (neither is the strap)
I like the pipe with flattened ends, looks neat
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: LJ. on 22.04. 2010 08:51
Oh no! Just realised that I could be responsible for your confusion... I've posted  pictures of a swinging arm tank and not a plunger. Think I need to go out and look at my Plunger Star Twin's frame, although a 1949 early frame might be different to later A10/7 frame. Sorry ignore my last post.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: muskrat on 22.04. 2010 12:50
Yes Darren, my '51 hasn't got the block or strap under the tank. The plunger tanks are mounted fore and aft so are not as prone to splitting.
Cheers
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: beezalex on 23.04. 2010 13:55
I believe the tank strap was introduced around '52-'53 for A10's only.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: MG on 23.05. 2010 17:56
Just wanted to add my solution.
I cut a trapezoidal strap from stainless, long enough to reach back to the bracket that is welded to the frame. You can also see the small piece of light-brown rubber inserted between the strap and the bracket.

This way, the strap not only holds the two tank halves together, but also holds the front part of the tank down to the frame, thus relieving the strain on the centre bolt. I thought that would be a good idea as the bracket/nut for the centre bolt needed welding on both my frames. Worked out pretty well so far.

Cheers, Markus
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Big Nick on 23.05. 2010 20:44
fit a strap !
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Sunbeam on 07.07. 2011 15:36
Anyone know why there are upper and lower antiroll rubber positions on the swinging arm frame.......(smaller tank?) I've bought 2 such straps in the past due to the original being missing and having problems fixing the front of the tank.
Each strap I bought was different, one was shaped (2 double sets in it) the other was flat. When I push the tank down on the top tube foams and anti roll rubbers,the bottom of anti roll bracket still looks as though it will interfere with either of the straps. I'm still unsure which position to fit the anti roll rubbers! Also, I can confirm that leaving this strap off will damage the tank.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: RichardL on 07.07. 2011 22:51
With but the pathetic experience of owning only one A10, and only having owned one A10, and being in a place/city/country where seeing another A10 at-large might happen every 10 years (if at all, as the only time I've seen another, while living outside Chicago since 1992, was at a vintage British vehicle show), I still have an opinion. And that is, I think the upper hole carries the bumpers when a 2-1/2 gallon tank is fitted, as is the case for my bike. From photos here on the forum, it appears the lower hole is used for the larger 4(+) -gallon tank. Ipso-facto, if I've interpreted it correctly, the bent straps should be for the 2-1/2 gallon and the straight ones for the larger tanks. In my case, as you've seen, no bent strap, instead, straight throught the lower hole.

On another point. I had to shave down the bumpers to get where the tank was a sane fit over them.

Richard L.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Sunbeam on 08.07. 2011 13:03
Thanks very much for the info Richard. I've a 4 Galllon tank fitted so it looks like bottom holes for the rubbers and use the flat strap.

Howard.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: RichardL on 08.07. 2011 13:54
So,  does it all line-up for that?
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Sunbeam on 08.07. 2011 16:40
Hi Richard. Flat strap just about picks up if I push tank down hard. I'm sure bike's previous owner left it off due to central tank bolt cup being missing. All thread stud + thick rubber washers + nut  & washer have been used to pull tank down onto the frame top tube. Are the strap retaining nuts BSF or Cycle? Know the question was asked somewhere on the forum but I can't find it.

Howard.   
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: RichardL on 08.07. 2011 17:18
Nuts!  ...............Parts book not handy, so thin on research material, but think they are probably BSC. Others can, please, chime in now.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: bsa-bill on 08.07. 2011 20:25
Pretty sure they're cycle. Haven't got around to fitting the strap on the RGF as yet
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: MG on 08.07. 2011 20:50
Yo, 5/16 Cycle
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Sunbeam on 09.07. 2011 00:00
Thanks all for the info on strap retaining nut threads. I'll now run a 5/16 BSC die down both of the tank stud threads.....chrome plating had been left on the studs.

Howard.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: tommo903 on 11.08. 2017 10:10
I know this is an old thread and judging by the date, it's obviously something that doesn't get talked about very often. However, I was surprised to read about the importance of fitting a tank stiffening strap and the likely consequences of not doing so...so thought it might be worth resurrecting for some of the newer A7/A10 owners like myself.

Anyway, the strap on my A7SS is missing and so far, I have bought three from different sources. The first two didn't fit (distance between holes too short) so they went back. I've now just received another from a well known dealer and whilst it fits, it's not a flat bar I was expecting to see as shown in the parts book (not in the greatest of condition either!) So I'm wondering if anyone knows what bike this was intended for?
Anyway, given what has been said on this topic I think I'll just paint it and fit it...better than riding around without one.

Steve


Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Greybeard on 11.08. 2017 10:19
I made one from scrap stock.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: tommo903 on 11.08. 2017 11:17
Judging from what dealers are selling GB, that's probably the best way to go!

I don't have anything at home that I could use but I'll pick something up at the next autojumble visit.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Greybeard on 11.08. 2017 11:19
Judging from what dealers are selling GB, that's probably the best way to go!

I don't have anything at home that I could use but I'll pick something up at the next autojumble visit.
B&Q would probably have something suitable. Doesn't need the offset; at least not on my Plunger model.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: muskrat on 11.08. 2017 21:31
The tank (original I think) on my A7 plunger doesn't have the lugs. Possibly due to the A7 tank being smaller than the A10.  *dunno*
Cheers
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: trevinoz on 12.08. 2017 00:49
Tommo, they usually aren't a flat bar and have the two double sets as you show.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: tommo903 on 12.08. 2017 08:54
That's interesting Trev...I was just going by what's shown in the parts book...not that they're always correct!
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Stikkan on 12.08. 2017 20:52
Hi all,


I found this on ebay: http://www.ebay.co.uk/itm/bsa-a10-a7-b31-b33-gold-star-etc-tank-support-bracket-/112504888848?hash=item1a31d05e10:g:7HYAAOxyzqdTd81o

And here is another:
http://www.ebay.co.uk/itm/Bsa-Tank-Support-A7-A10-G-Star-And-The-Bsa-Import-Model-Made-OF-S-Steel-/322638672404?hash=item4b1ec37214:g:iDcAAOxyOMdS-mTj
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: Greybeard on 12.08. 2017 21:18
Just flat stock
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: trevinoz on 14.08. 2017 22:10
I assume that your bike is a swinging arm, Tommo?
These straps are double set to clear the centre rubber buffer bracket.
Oddly it doesn't foul on every frame/tank combination.
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: tommo903 on 15.08. 2017 10:51
Yes Trev, my A7 is a swinging arm.
When I fitted the tank strap I have (with double set) I did notice the rubber buffer bracket that you mention and thought perhaps that's why the set is there, but then realised that a flat strap would have cleared it anyway  *conf*
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: bikerboy on 22.08. 2017 21:54



anyone know why there are upper and lower antiroll rubber positions on the swinging arm frame
----------------------------------------------------------------------------

To answer the question even tho its an old thread. The lower holes are not for rubbers but were used for the sidecar mount
Title: Re: 51 Plunger Tank Strap and other questions.
Post by: trevinoz on 22.08. 2017 22:08
Never seen a sidecar mount there.