Hi,
in the interest of forum etiquette, I have been searching, fiddling, photographing and gps-ing before asking.

Please note; i am a vespa mechanic so I am dumb enough to try it myself and smart enough to ask those who know. Never worked on one of these before.
Also i know fuel mileage talk is lame, but when it is half and there are no leaks there must be some power available somewhere when it is put right.

OK. here's a list of facts. I am hoping there's a simple thing here, but the DC seems to be getting less than half what the 'internet' suggests.

facts:
1600 2-port
34PICT-3
seems to be running ok
runs like a baG o' S*&^* for about 2km in the morning
USED 38 litres (same pump same level) to travel a TRUE 170km (GPS)
that's 22 litres per 100km commuting 9km twice a day

ACTIONS:
last night I checked and the choke butterfly wasn't sitting vertically (probably 15-20degrees from vertical) can this have any effect?
This morning i loosened it and turned it around to make sure it is disabled for the time being. (vertical).

I left the idiot book and bentley at home so i followed the instructions online to adjust the bypass and volume. it only really would idle with the bypass three quarters - one turn out (internet said 2.5 turns start) Is there a clue here or is it normal?

from my experience with 2 strokes, the main cause of unfathomable fuel use when driven by newbies is a badly tuned idle jet causing the rider to throttle up straight to main where there is some power. Any input here would be great.

Cheers
derek
happy to answer and scooter questions.

What distributor do you have?

What colour is the inside of your tail pipe (brown or just black?)

How old is the engine? Good compression etc? When worn (like my baja) you gotta bury the foot to compensate for lack of power.

Are you running any exhaust apart from stock?

When was the last time you serviced your air filter? What condition is it in?

Drum brakes on the rear properly adjusted? (ie: no brake drag)

Tyre pressures correct (not lower than spec)?

Wheel alignment up to date?

Thanks for the reply

Oh forgot , the tailpipe is a Dickensian chimney.
sweeping my finger inside completely coats it with a thick layer of jet black powder.

My guess is that your heat risers (which heat the intake using the exhaust) are blocked. That would definitely explain the bad initial running and probably be a factor in the poor fuel economy. Check out here for more info including how to unblock them:

http://www.vw-resource.com/heat_risers.html

Float levels
fuel pressure overcoming needle and seat
rotten ignition leads,rotor or cap
spark plugs/gap

you got alot of things to check ahead of you my friend,

Apart from float levels, choke, etc. you should check that the main jet is firmly screwed into place. Easy to check; if it is loose or perhaps cross-threaded) will use heaps of fuel. (Could be totally the wrong size too...)

plugs and main jet inspection today (mixed with a smattering of superficial stuff like door cards)
since getting the choke off I have made 70km and its at the 1/4 mark. I know, i know the gauge means nothing. i'm hoping to tackle Nils' list with 250km per 40litre as a starting point.

Also is the cooling system up to scratch.....lots to check yet, but to answer one of your questions, yes the choke will influence economy and should definately be off/verticle once warmed upA photo tells a thousand words, post up some pics of your engine bay, carb dissy even outside engine lid rear louvers and what not can influence things.....on one of these wierd air cooled automobiles.