Failed tank liner

I have been having intermittent problems with fuel starvation. The effect of this has been running on two cylinders, cutting out, then restarting after a few minutes at the side of the road. I know it is a fuel starvation problem because the bike would run on either cylinders 1 and 2 or 3 and 4: both combinations are served by both coils so coil failure could be responsible. I have had trouble with one or other of the petrol pipes doubling over and cutting off the supply to the left or right pair of carbs. Also, I have fitted two clear fuel filters into the petrol pipes and so I could see them empty of fuel when the bike has come to a stop, and then gradually refill. I figured that flakes of the liner were probably wrapping themselves around the filter that is integral with the petrol tap, thereby restricting the flow of petrol through to the carburettors. I had previously had a go at removing all the loose liner from my petrol tank, including fishing in it with a spring-loaded grabber tool and then draining it entirely. I managed to get a lot out and thought the remainder was sound. However, the return of the starvation problem suggested otherwise. I was pretty sure that once again the failed liner was at the root of the problem so I decided to try getting some more of it out.

I used my grabber tool again and soon found it wasn't hard to fish out large flakes of the liner that had come loose inside the tank and was floating about in the petrol supply.

In the photo above, you can see the size of these flakes in relation to the petrol filler.

So after about 30 minutes of work, I managed to get a considerable amount more of the failed liner out of the tank. I'm pretty sure there aren't any other large flakes there right now but I'm equally sure more will come looses and foul the fuel outlet once again.

A Trip to Trevor

I took advantage of the slightly less appalling weather today to visit Sprint Manufacturing at Upton Lovell in Wiltshire. Although the air temperature is pretty low now, with the damp taking effect, it was a nice run out. The sun lit up the gold and russets in the trees along with the remaining green leaves along the way.
Trevor is the Chief at Sprint Manufacturing. His premises are well off the beaten track, business being overwhelmingly made up of web and telephone mail order. It's not a big trip for me to get there in person though and a nice ride to boot. I found him in the midst of applying a gel coat to a hugger he was making for an Australian customer. A top quality job, needless to say. He told me the classic fairings side of his business are popular in Japan, to the tune of an order a week in the summer.
Anyway, Trevor has helped me out on many occasions, supplying good advice, good parts and good humour at all the right times. Several times on previous visits, I'd said I'd bring my 1200 for him to see when it was finished. I'm sure he's seen dozens of the things before so it was more of an excuse for me to get out and seek approval from the master than a case of me showing him something new.
So I set the bike up on its centre stand, started the motor and asked him what he thought. Here he is, focusing his full force of his mystical powers to commune with the inner workings of a T300 in action:

He was impressed with the quietness of the motor compared with others of its ilk. He told me the early die-cast cases (with access hatch for sprag and alternator drive gears) are noticeably quieter than the later Cosworth pressure sandcast cases. I forgot to say that the 1991 bikes have foam-lined fairing panels too, dampening the sound further. And the result. Well, was it in doubt? I think it met with his approval.

The bike had run beautifully all the way there. Irritatingly, I had more fueling problems on the way home. Maybe the bike was sad to have had to leave the cosseting world of Sprint. But seriously, I think I've got four issues to deal with, two of which are probably self-inflicted. 1/ The loose sheets of liner are wrapping themselves around the fuel tap's integral filter 2/ the fuel tap prime position isn't passing any fuel, 3/ the angle of the extended fuel pipes and filters I fitted seems to be causing at least one hose to fold. 4/ The extended pipes are also putting pressure on the vacuum pipe to the rear of the fuel tap. So I shall address all these issues before taking her out on the road again.

Fuel cap

I wanted to make sure my fuel cap was functioning properly. I have had some problems with the breather on the identical item on my 900. It has occasionally failed to admit sufficient air into the tank to allow fuel to exit, especially after a period of high speed running.

The cap is an aircraft-style flush filler cap, operated with a key in spring-loaded mechanism. The key hole is itself hidden under a sprung cover. This cover was loose, not snapping shut, and the key was not centering after the cap was pushed home. Not a big deal but I thought I'd see if I could clean out the components and restore some snap to the action.
The main components of the cap are visible above, including a lid with rotating centre that is hinged to an alloy ring; a retaining tang which is drawn back by the two pegs on the rotating centre; a small spring which forces the tang out to retain the lid by clipping under the forward edge of the tank's filler hole; the main fuel seal which is held against the tank's fuel filler hole by four small springs; a tang retaining cover, and steel retaining disc and two screws which clamp the tang holder and seal in place.

The fuel tank breather is a small air passage that runs from a little hole in the tang retaining cover, through a casting that contains the lock barrel, and through a pair of diaphragms to another little hole next to the hinge. The tank emits a rather attractive humming, whistling noise when in the sun or cooling down after a run. The noise is made by fuel vapor escaping, or air being drawn through these diaphragms.

The little holes are indicated by the tip of a screwdriver in the pictures above. The left-hand picture above shows the cap without the main fuel seal in place. The four small springs visible around the rotating body apply pressure to the main fuel seal to ensure it works effectively. The right-hand picture shows the cap reassembled.



The cap assembly is retained by four screws into the top of the tank. One is under the lid, preventing the cap from being removed without unlocking it first, the other three are allen-headed screws that pass through the periphery of the hinge ring. Two of the allen-headed screws are just decorative. A rubber dust and dirt seal fits into the top of the tank first, followed by the cap hinge ring.



I cleaned off all the corrosion from the components and lubricated the rubber seal with rubber grease, and the spring-loaded tang with copper grease. I replaced the inner screws with stainless items. Job done.