Petrol pipe bore for the 250 2C to suit the fuel taps and carb inlets

[julianharty]

An oddity to me, and perhaps to the model generally, is that the fuel taps I've been supplied with have smaller outside diameters than the carb inlets. As I've several sets of taps (that came from various sources) this seems to be as intended by the factory.

What works for your 250's and what would you recommend please in terms of fuel pipe for the fuel taps to the carbs?

[Steve Brown]

I've come across this with other models too. Lately I've been buying and using silicone rubber pipe as an experiment. It's not specified for fuel but it is very flexible and stretchy so can be made to fit a couple of spigot sizes with undue stretch. I have it on 2 bikes now and it seems to be lasting well with no signs of distress. No hardening either so easy to remove and refit tanks without leaks from a stretched pipe. Cheap enough to make the experiment worth trying. Bought mine from ebay.

[julianharty]

Steve, thank you for the suggestion; I've ordered several metres of 5mm ID clear and 5mm ID in black.

PS: My 250 2C is now running tolerably well considering it was last on the road in 1988. I used a small portable fuel tank for the testing and it's managed a few metres under its own power on the drive. Still various work to do before it's roadworthy however I'm very encouraged with today's progress.

[Ming]

I used silicone pipe on several bikes successfully. On the 250 I resorted to an internal sleeve at the tap end. Perhaps a technology whiz could make a few suitably sized adaptors using 3D printing?

[Parker3865]

I too have sleeved my pipe at the tap end. Hadn't thought of printing an adapter, I just cut a piece of smaller pipe to fit. I can try printing in TPU if anyone wants to try them.

[BarryCambs]

Mine's the same and it has sleeves on the fuel tap. The sleeves are in need of replacement though, so if anyone comes up with a neat solution, Id be interested.

Barry

[Arthur Farrow]

What did you sleeve the fuel tap with ?

I bought a 250 recently and the first thing it did yesterday after leaving the fuel on for 8 hours (no good marking for OFF) was to dump all its fuel on the garage floor as it had inline filters fitted that had gone soft (thought to be Dellorto ones from the UK importers) It was a real mess so cleaned up the several gallons on floor and pulled the whole pipework off.

Pipe was silicone and had gone white....now confirmed as a year old so not ancient....and discovered the disparity of pipes....have ordered 2 brass reducers off e bay ..from China so we have to wait...with unequal size barbs 6mm and 4mm and lets see if those sizes work

Simple solution would be to replace taps but need to ascertain thread size...does anybody know......my rotten lungs are reluctant to pull the taps off they have had enough fuel vapour for several large explosions like Mr Creosote in the Monty Python sketch.

[Ming]

Sorry Arthur, it was some time ago and not something I noted - though probably from China (isn’t everything?). I never managed to find a stepped adaptor, or the tap thread size. I used Honda step-through taps, which were not handed, so indicated arsy versy whether on off or reserve. It was fun!

[Arthur Farrow]

SOLUTION !

Vespa part on e bay .....Fuel Hose Metal Connection Banjo DELL'ORTO PHBH/PHBL, straight 6 mm,

This enables you to plumb the whole lot in narrow bore pipe on a simple one tap to one carb basis OR put a 6mm "X" 4 way connector in circuit

I doubt the smaller bore pipe would make any flow issues as the taps themselves are so small.

[julianharty]

Thank you Arthur and what a good solution.

I've ended up ordering a couple of sets worth from https://www.vespajets.com/product/fuel- ... ight-6-mm/ as they worked out less expensive even after the £3.90 P+P.

I'll try them on my orange 250 2C when they arrive. As you noted, their smaller bore won't restrict the flow (especially as the fuel comes out of the taps with the same small bore).

[julianharty]

I realised after ordering these cute carb inlets that they have a single nozzle rather than the two on the current ones. So no more fuel balance pipe between the carbs. Oh well

[Steve Brown]

With a 'T' piece in the pipe that might make the pipe routing easier Julian? Useful on a Kanguro perhaps too?

[Arthur Farrow]

Yes single outlet not double BUT you can buy a 4 way brass 6mm fitting if you feel it necessary

I have now received the 2 fittings for my carbs and fitted them on the basis one carb one tap...I have ordered a 4 way fitting but has not arrived.

Having one tap one carb makes routing so much easier not having the between carb balance pipe and one of my pre war twins has a similar arrangement so no sweat

ONE THING TO NOTE ! The internals are a little different and the bolt does not do up fully before bottoming out.....I decided not to shorten the bolt but to see if a washer under the head of the bolt did the job....It has to be thick so I used a 6mm bore spring washer which I straightened out

This works just fine.

Not having had the taps off I assume they are both ON OFF RESERVE ?? or is one a reserve tap and one normal ???

IMG_0250 x.jpg (21.89 KiB) Viewed 7153 times

[Arthur Farrow]

AND ANOTHER SOLUTION !

attachment=0]IMG_8996 x.jpg[/attachment]

I assume these will fit but need longer screws. These are Dellorto model 8796 6mm outlets and they are in stock at Eurocarb...used on the 250 T Morini single..you can see one on my sectioned engine which will be at the Morini Rally this coming weekend

Angles not really satisfactory but another solution!!

[Steve Brown]

Arthur, I'm pretty sure that Dellorto list those bolts in 2 lengths for the different banjos. I've found oddities on some bikes too.