You drew that. Thanks for the kind effort, I hope it wasn't much trouble, as drawing in software can be, off the cuff. Perhaps you scanned it in. its as I imagined, but clearer. I'll give it a go, I'll measure up straight away so I can get the piece ready whilst bike set up for riding with new pump fitted - unless I get lucky with stock and time. Imagine I won't have to remove the filler cap a second time if I do postpone it. I'll let you know how the vacuum pump performs. John
I already had the nut drawing as a jpeg............I just did the rest with PShop........3 minutes approx. The lower end of the plug and flange should be exactly the same as the lower end and flange of the sensor...........I reckon the total thickness of the plug can be at least 15mm - 20mm. Looking at petrol taps, I think the bore has to be an absolute minimum of 6mm.....the Facet pump sucks as well as pushes............the OEM petcock I think is 8mm bore and I'm not sure if the OEM pump sucks as well as pushes............ Some Harley petrol taps are large bore.
A 3/8" british fuel tap would fit the bill then. I'll also look into a Harley - being metric that's a good idea.
I measured the original OEM petcock and the ID is just 4.5mm at inlet and 5mm any the stub. The original rubber fuel pipe is 7 x 12 mm. The steel fuel pipes in the tank are a 5mm bore. So, the OEM petcock represents a restriction, however I suppose Ducati didn't overlook that, but considered it OK, given the pump construction and, importantly, that flow pressure loss is a function of bore times distance plus bends (as per gas and water plumbing knowledge). Its the flexible hose that is greater distance. I'm pretty sure Ducati would have calculated and measured the pressure flow at pump and at carb, having chosen the hose to match. I'm thinking therefore, that the bore of the petcock perhaps wouldn't benefit from being greater than 5mm. Also, that folk may be renewing their hose with 5 x 10mm rubber nitrile hose to match the inner bore of the steel tubes, and if so, that would be a mistake, accordingly (to the above). Its possible, I imagine, that the pump performs better pumping into a 5mm bore initially, rather than seven, in order to build pressure (pumping with the largest pump in the world into a vacuum - the liquid/gas would lose pressure almost immediately!). Well, that's the principle of having exhaust pipes with smaller bores than tuned end cans... it produces a scavenging force with wouldn't exist if going into the much lower local planetary atmosphere. Incidentally, earlier and smaller gravity fed petcocks in British systems are generally 1/4" or approx 6mm, and larger are 3/8" or approx 9mm... which tells us something... I suppose...although ineffable. Its a benchmark by comparison.
Don't forget that the OEM set-up doesn't produce a great deal of pressure...........only 3psi - 4psi............. It only needs enough pressure to deliver a flow to the float bowls, keeping them topped up, particularly when the revs are higher.......the return pipe negates most of a slightly higher pressure anyway. However, bear in mind the float valves let go at about 12psi, so if the pump pressure was increased say above 7psi - 8psi , the return flow may not be fast enough to completely ease excess pressure on the float valves.
Yes, good points here. As i'm going to use a vacuum pump, I feel safe in that area. I don't know what psi the pump is, only that its 20 litres per hour, about right for a 75 BHP engine, on the limit (tight side) for racing but adequate for occasional full open throttle. Incidentally, whilst I'm working on a solution for a suitable fuel tap to do away the reserve, I'm going ahead anyway with the vacuum pump and a vacuum stop valve (waiting for the latter to arrive). The main thing in question here then is that I've run a tube with sock-screen on end to the uncut in-tank original steel pickup tube, which feeds the stock OEM petcock. That entails a slight rise of about 4 - 5 " from bottom of tank. It would't be a potential problem if I were to fit a brit-style petcock immediately in place of the fuel gauge, of course, and that's a good reason to tackle that option immediately. Now, I'm using a Monster's vacuum pump, and not sure what the Monsters internal tank set up is, in that respect. However, I have report of this method being found to work well on a supersport. But I am also tempted to cut the original pipe short right now rather than have to do it later, if necessary. I guess I'll do it in stages, road tests, and risk having to empty tank for more work later. Unless someone can tell me not to bother trying such a set up to begin with!
I would remove the pump and filter and join the pipes as necessary with some suitable tubing, but I would still leave a bag screen in the tank, although if a filter was fitted before and after the pump it probably wouldn't be necessary especially if the Brit type tap has a gauze filter as well.
Here's the kit I've fitted, somewhere just after the fuel filter, visible under tank, is also a vacuum fuel stop valve. Pumps the fuel on start and seems to ride fine around the town with little dashes - yet to test on open road. John Sent from a mobile transmitter.
