A forum for owners of Yamaha TTR250 trail and enduro bikes!

Following prompting from Brian, I shall now attempt to give some help regarding changing the lock barrel on an OE fuel cap:

1: Give the whole cap a good soaking in penetrating oil to loosen up any dirt and rust

2: Undo the 2 screws that hold the locking mechanism in place, taking care to hold pressure on it as it's spring loaded and there are 2 small springs that have potential to fire into the furthest corners of your chosen place of work!

3: Flip out the washer then prise out the o-ring beneath with a pin.

4: Tap the cap firmly on something hard until the metal spacer ring comes free (this is where you hope the penetrating oil did it's job!)

5: If you look down the space where the metal ring came from, you should see a brass "tang" (hopefully visible in the next shot...) This needs to be pushed in towards the centre of the lock barrel until it's flush, with something thin and strong, while simultaneously putting some pressure on the lugs on the end of the barrel. When it's flush enough, the barrel should pop out!

Here you can see 5 locking tangs and the retaining tang (a slightly different colour) at the end. These are spring loaded, and have the ability to turn invisible when they hit the floor!

6: Make sure all the tangs in the new/replacement barrel are clean and move freely. Lubricate with light oil or graphite grease.

    Down the centre of the fuel cap you will see grooves that the tangs seat into to prevent the barrel from turning without the key. Depressing the retaining tang with a small screwdriver, insert the barrel in a position such that the tangs DON'T go into these grooves, otherwise the barrel won't push in far enough. Be careful not to accidentally flick any of the locking tangs or they will make a break for freedom! Once the retaining tang has started, the best way to push the barrel into place is to insert the key so that the locking tangs go flush and the whole thing clicks into place. Turn the key to make sure it all moves freely half a turn each way.

7: Check the locking tang is fully out and refit the metal spacer, o-ring and washer. When replacing the locking mechanism, make sure the lugs on the end of the barrel line up with their notches before you tighten up the screws, and try not to cross thread the screws as the plastic is quite soft.

That's it. I take no responsibility for blindness caused by locking tangs flicking in your eye, or divorce proceedings resulting from dents appearing in the kitchen table whilst knocking the spacer out!

Best of luck,

Simon.