TDR Fuel problem

[Liono]

I have just bought a tdr 125, but have been having a problem with the fuel. The fuel tap has 3 positions; on, off or reserve, and has 2 pipes leading into it (for main and reserve I assume?). The bike runs fine on the reserve, but if I switch it to the on position it dies. The engine doesn't cut straight away, it takes a minute or so if I am already running it on reserve, which makes me think that something is blocking the main fuel line somewhere. I have two questions really:

1) What should I be looking for to try and sort the problem out?

2) I was told that on some bikes the reserve just takes the fuel from lower in the tank - if this is the case, could I run the bike with the switch on the reserve position until I sort it out?

Thanks to all the people who gave me advice on another thread about starting flooded engines - I now reckon it wouldn't start because I had the fuel on main rather than because I had flooded it

[Smoto Bob]

could just need some more petrol

tdr good bike mate , yes they do have two pipes and yes ones higher, or they would both run out at the same it take it out and test it, clean it and blow the wrong way through it( useing the diffent posisions On would be the problem one).
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[Liono]

Just to clarify, I have filled it up with one of those 5L petrol cans which seemed to fill it right up to the top (I don't know how much was in before) although it is hard to see how much is in as there is a metal flap thing in the way. How much petrol should the tank hold roughly?

[badlydamaged]

Apparantly the fuel tank size is 15 litres mate
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[stinkwheel]

On bikes with a fuel tap like that one of the pipes coming off the tap is usually the fuel supply to the bike, the other is usually a vaccuum tube which connects to the casting just in front of the carburettor.

When the engine is running, air is sucked through the carb past where the vaccuum tube attaches to it, the bourdon? effect causes a vaccuum in this tube. There is a rubber diaphragm inside the fuel tap that stops fuel flowing out when the engine is stopped. When the engine is running, the vaccuum sucks this diaphragm open and allows fuel to flow. Sometimes the RES position allows the fuel to flow under gravity without the need for vaccuum.

The fuel can flow through the tap from one of two holes inside the tank, switching from ON to RES switches between these holes. The reserve gives you a little extra fuel because there is a vertical pipe of about 2" long attached to the hole corresponding to 'ON'. Fuel runs out of the tank until it reaches the level of the top of this pipe at which point it stops. Changing onto reserve at this point switches onto the hole with no tube allowing access to the 2" of fuel left in the bottom. Most bikes have a gauze tube over the whole arrangement inside the tank to stop bits of muck getting through.

So possible problems:
Not enough fuel in.
Vaccuum tube has become detached.
Blockage in fuel filter.
Blockage in fuel tap.
Malfunction of fuel tap.

To answer 1 (you will have worked this out by now if I have explained things properly)
Check there is enough fuel in.

Check the vaccuum pipe is still attached at both ends.

Check for a blockage in the filter by draining the tank into a suitable container, removing the fuel tap from the tank (usually either a single nut or held on by two screws, be carefull not to burr them as the metal is soft), washing the filter in some clean petrol and blowing it dry with some compressed air (if available).

Check for a blockage by blowing back through the fuel tap from the bottom with the tap in the ON position (with the tap removed from the bike for obvious reasons), this should clear it. If you can't blow through it, there is a more serious blockage or a fault on the tap so you will have to....

Dismantle the fuel tap, I don't know what yours looks like so can't give specific help, some can't even be dismantled.

To answer 2)
Yes you can, but be aware that any dirt sinks to the bottom of the tank, using the RES position takes fuel from the bottom of the tank so you could land up with dirt in your carburettor. If you run out, you are pushing!

<EDIT> There is a rubber O-ring that seals the joint between the tap and the tank, ensure this is in good condition and seated properly before reattaching the tap. If it is damaged, replace it.

A workshop manual will explain this better and with pictures. Try to find one if you want to do your own servicing.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

[Liono]

Looks like I have a day of taking the bike to bits tomorrow then, a great way to put off all of the other work that I should have done weeks ago Thanks for taking the time to write that out Stinkywheely, I am trying to find a manual for the bike, but they don't seem to be especially common - Haynes don't do one.

[Smoto Bob]

tdr ( guessing the same as dt) doesn't have a vacuum style tap so when he turns it to main fuel should pour out (if he takes pipe off)
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F'it DO WHAT EVER MAKES YOU HAPPY!!!!! Even if it screws over everyone else :p
Titz wrote: "..and my 3rd accident was when this police car....."