Hi Gary. Although you could indeed have a fuelling problem, I'd expect that the carb float chamber would even out the flow to some extent. The bubbles in the fuel when warm could be vapour which (in moderation) shouldn't matter - the engine drinks the "beer" from the bottom of the float chamber and ignores the "froth" ! If you get a sudden, on-off change in power it possibly points more to an ignition problem. The firing voltage goes up when cylinder pressure increases under load as you open up the throttle for a hill, exposing any weakness in the spark generating department. See my article on ignition condenser failure when hot on the Dorset A7 club website.

Location: New Forest

Hi John

Thanks for the reply, I understand what you are saying, I don't have a condenser or points, my ignition has electronic with the AccuSpark magnetic switch, so just a rotor arm, nothing else - the dizzy was rebuilt by Distributor Doctor & has a red rotor arm supplied by him.

The bubbles are not just the odd one or two, but a busy stream, nothing when cold, but when at working temperature they flow!

I think the source of the tissue may have been identified - petrol forecourt - they have those blue rolls of tissue, someone could have wiped the nozzle with this and a swatch attached itself and got flushed in when I filled up with petrol (only done this twice), the tissue was blue & it would explain how that got in the tank, the gauze over the pipe is long gone so un-protected against any foreign body.

I have ordered a new diaphragm to have on standby and I will take the pump apart & re-seal it...

Location: Saltdean, Brighton

Just to conclude this thread, I renewed all the fibre washers and applied ptfe sealant to them all and the steady stream of air bubbles when hot have ceased, just the odd one now & again.

Thinking about it some more, the domed top to the fuel pump is on the supply side and will hold a certain amount of air, so it was probably this that was not as air-tight as it should have been (and hopefully now is) and this is the only joint that if not sound would not leak petrol, so now resolved.

I have today been over to my Uncle's, which was a round trip of 56 miles, 28 miles is the furthest it has ever done since the return to the road in a single go, not a problem under heavy load and that included going up & down Devil's **** both ways, which for those that know this, it is a steep incline and there was no hesitation in the fuelling, would have been nice to have had a bit my ooomph!

Thanks for the comments

Location: Saltdean, Brighton

For some reason **** is being censored, all it says is d-y-k-e, it is a place!!! Weird

D-e-v-i-l's D-y-k-e, East Sussex

Location: Saltdean, Brighton