Vespa Reed Valve Fuel Pump

[GLscoot]

I need to fit a fuel pump to my engine set up and was wanting to know what's the minimum distance below the reeds I can insert the banjo on the manifold. I think I have about 10mm and was going to use a 6mm banjo. I have also been advised on fitting a header tank to feed the carburettor, as feeding the carburettor straight from the pump may cause it to flood. The carburettor I am using is a PHBH (similar) 26 or 28mm with a Polini 180 Top End.

[Jack221]

Make sure you fit a smaller bore bypass line on the pump to drop the pressure and you won't need a header. You can also fit the pump vac line above or below the reeds, doesn't really make any differance for what you need.

[GLscoot]

So i can fit the banjo above the reeds, thats even better as i have loads of room on that part of the manifold. So i can also fit a bypass fuel line from the pump, where would i fit the other end of this line ?
I am not to bothered about the header tank, what size would you recommend the header tank be, I am hoping that 50 - 100ml would be enough.

[GLscoot]

http://www.flickr.com/photos/77271143@N03/8257546490/
So I can fit the fuel banjo onto the manifold just behind the rubber connection piece.

[Jack221]

If you have the Dellorto vac pump, the same as mine, it pumps way more than you need. So, connect the pump outlet back to the pump inlet with a smaller bore pipe (or restrictor tube or jbilee clip) and make a recycle line. When you get it running you can adjust the restrictor by test flowing it into a bucket. I fitted mine under the tank and forget its even there now.

[GLscoot]

But can I fit the pump banjo line above the reeds, this is my main problem. I really don't want to fit it to the crank casing. I think I understand what your saying Jack. I should be able to sort that problem out.

[Jack221]

Above or below the reeds makes little differance. Between the carb and the reed block will be fine. The vac pipe will make a little turbulance in the manifold but nothing like as much as the reeds make!

Looks like you have been pretty busy. What other tuning have you done? port durations? Compression? etc? Or does someone else do all that for you?

[OzOAP]

Some pumps are pullers, some are pushers. So how close you mount them to carb/tank can affect efficiency. Also the shorter the vac pipe the better.
I fit a small filter between pump and carb to act as a 'swirl pot' so the carb isn't affected by pulsing. Also a loop pipe return with restricter (carb jet).
Will try and sort pic.

[santacama]

I am using a Keihin PWK 35 in my Malossi 221 and I don't need a pump.

[GLscoot]

It's nothing to do with power, speed or size if engine. The carburettor sits slightly higher than the petrol tap and so doesn't get a constant feed of fuel.
It's a GS150 frame with a reed valve engine, so there issues with the fuel feed. I have built the engine so I don't have to cut the GS frame. So it's all about getting a steady feed of fuel to the engine.
The scooter ran fine on long journeys, but when I use it in the city it's crap and even worse uphill.