Tank Reserve Compartment

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Tank Reserve Compartment

Postby Chessiegolf » Fri Feb 28, 2020 8:10 am

Can anyone help please.

Does it matter which side of the tank is deemed the main supply and the reserve supply. The bike is a standard 1960 G12.

As much as I can see from looking at the underneath of the tank and in through the filler (not much) the tank appears symmetrical but of course there could be a weir in there somewhere.

Out of sheer habit, as I had always run bikes this way, I use the left side as the main and the right as reserve, but this could easily be wrong. I recently saw a photo of a G12 with a "Reserve" transfer on the left side so this got me wondering!

Any authoritative knowledge would be appreciated.

John

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Re: Tank Reserve Compartment

Postby cbranni » Fri Feb 28, 2020 8:49 am

Main and reserve taps are available to buy from most suppliers, the difference being the main tap has a higher entry pipe in the filter than the reserve tap. The main tap should be fitted to the rightside and the reserve to the left, this allows you to switch the reserve on while still holding the throttle open and maintaining speed.

Even after the reserve has run out by leaning the bike over or putting the front wheel on a higher level eg pavement, it is possible to get few more miles and the last resort is to blow into the tank, bet we all been there :D

Colin

Sorry everyone my G12 is a 1961 model and must have a different tank from previous models and has two different taps 026565 main and 024201 reserve.
Last edited by cbranni on Fri Feb 28, 2020 6:04 pm, edited 1 time in total.
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Re: Tank Reserve Compartment

Postby MalcW » Fri Feb 28, 2020 9:28 am

cbranni wrote:Main and reserve taps are available to buy from most suppliers, the difference being the main tap has a higher entry pipe in the filter than the reserve tap. The main tap should be fitted to the rightside and the reserve to the left, this allows you to switch the reserve on while still holding the throttle open and maintaining speed.

Even after the reserve has run out by leaning the bike over or putting the front wheel on a higher level eg pavement, it is possible to get few more miles and the last resort is to blow into the tank, bet we all been there :D

Colin


Also, parking the bike on the side stand moves fuel over to the LH side, so if the RH side runs dry there will (hopefully) still be more on the left.

Malc

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Re: Tank Reserve Compartment

Postby Rob Harknett » Fri Feb 28, 2020 10:06 am

Chessiegolf wrote:Can anyone help please.

Does it matter which side of the tank is deemed the main supply and the reserve supply. The bike is a standard 1960 G12.

As much as I can see from looking at the underneath of the tank and in through the filler (not much) the tank appears symmetrical but of course there could be a weir in there somewhere.

Out of sheer habit, as I had always run bikes this way, I use the left side as the main and the right as reserve, but this could easily be wrong. I recently saw a photo of a G12 with a "Reserve" transfer on the left side so this got me wondering!

Any authoritative knowledge would be appreciated.

John

Guess you do not have an Instruction book, it will save you time asking many questions. You will also need a parts list. On Driving the bike, you have only reached point no. 2 and have asked a question. The first being fuel to use. Read all the book before you go any further, get to know what you have got.

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Re: Tank Reserve Compartment

Postby Chessiegolf » Fri Feb 28, 2020 11:08 am

Thanks for the speedy replies and it makes sense to nominate the right hand side as the main feed.

I've changed both taps as the old ones were well worn but it didn't occur to me that they could be made differently, so I've either fitted two lefts or two rights.

No, I don't have an owners manual only a workshop manual so I'm afraid I'll have to ask silly questions, but as they say........you are never too old to learn.

Thanks again for the replies.

John

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Re: Tank Reserve Compartment

Postby alanengineer » Fri Feb 28, 2020 12:58 pm

look at your parts book and you will see that you need 2 of the same petrol tap. If you dont have the books, search Christians archives. Lots of answers to questions that havent been asked yet.
best of luck

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Re: Tank Reserve Compartment

Postby Rob Harknett » Fri Feb 28, 2020 1:37 pm

An Instruction book was issued with every new machine. So should be considered part of the bike. If missing, it seldom seems to become a part wanted.
A parts list can also help you. In the first instant it will tell you a parts name. So you do not get stuck with " has anyone got the bit that fits on the bit......... "

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Re: Tank Reserve Compartment

Postby Duncan » Fri Feb 28, 2020 5:23 pm

Hi John

This is a link to the 1959 Owners manual on the Archive, others are on there as well: http://archives.jampot.dk/book/Owners_manuals/1959_Matchless_Instruction_Manual_All_Models.pdf
http://archives.jampot.dk/

Generically, the left hand side of the tank is slightly larger than the right hand side due to the shape of the cutaways underneath, hence this side is normally treated as the reserve. Your petrol taps should not have the reserve spigot/pipe on them if they are single function (on/off) taps. if you do use pipes with spigots/pipe on them fuel can be left in the bottom of the tank on one side of the frame tunnel that you can not access.

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Re: Tank Reserve Compartment

Postby Chessiegolf » Fri Feb 28, 2020 6:00 pm

Duncan,

Thanks for posting the instruction manual, that's indeed helpful.

The new taps I fitted are the modern push/push type with o ring seals. The old ones with cork seals both seeped and one day when I went to turn on a tap, and on a return journey, the round end came straight out - followed by a nice flow of petrol. The retaining screw had worn to the point that it no longer acted as a stop. The new ones are much better if not in keeping with the original, but that's of little concern to me.

Colin's reply that using the right side as the main feed made a lot of sense in being able to switch to reserve while still holding the throttle.

It doesn't seem to be covered in the book, but have you any idea of the likely range on reserve - I realise that the bumpiness of the road and lean angles prior to running dry will have an influence, but are we talking 1 mile, 10 miles, 50 miles? I have no intention of putting this to the test, but one day it could be comforting information.

I will now try and use the right side as the main, but unfortunately the brain is fading and it may be a case of old dogs and new tricks!

Thanks again for the help.

John

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Re: Tank Reserve Compartment

Postby Greybeard » Fri Feb 28, 2020 6:23 pm

While the weather is duff, why not drain your tank using the right hand tap, then switch to the left one and see how much more you can drain out? That way youll know how much your tank holds as a reserve. Only you can judge how many miles youll squeeze out of what's left.

Steve

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