polo2k wrote:ill have to try it without the carb I guess because it pours out perfectly when the outlet pipe slips.
Exactly - take feed pipe of carb, turn tap on, if you get lots of petrol pouring out, then at least you have eliminated the fuel feed issue! *
BTW - I have lots of experience with bike engines, but haven't commented yet because it's difficult to be sure when I can't see the thing.
You have 3 pipes? My guess would be:
1) - fuel feed - self explanatory
2) - possibly a vacuum feed to a vacuum fuel tap *
3) - not sure about the 3rd one - possibly just an overflow pipe going to fresh air.
Personally I'd be taking the carb apart ond testing/blowing down the pipes to see where they went and what they did. If in doubt, blank the pipe off, otherwise it will probably introduce too much air into the intake, upsetting the mixture.
* Many (or possibly all!) modern bikes have a vacuum tap. A conventional tap requires the rider to turn it on and off before and after each trip. The problem with forgetting to turn it off, is that any leakage past the float needle (and there will probably be some, especially on a bike parked on a side-stand, and therefore left leaning at an angle) will quite often dribble down into the cylinder. At best this will flood the engine, in the case of a 2-stroke, at worst it will dilute the oil and cause all sorts of problems, in the case of a 4-stroke.
To avoid this, manufaturers fit a vacuum tap. This is held open by manifold vacuum, but as soon as the engine stops, the vacuum collapses and the tap closes. Of course you need to create some vacuum in the first place to open the tap to atart the engine, and usually turning the engine on the starter is enough to do this. However, on a multi-carb bike that has been left standing, the float chambers will have evapourated dry, and it can take a lot of cranking to make the tap open long enough for them to fill and start the bike. For this reason, many bikes have an additional feature on the tap which is "prime" - it bypasses the vacuum mechanism to enable the carbs to prime manually.
If your bike has a vacuum tap, or if the carb was intended for a bike with one, then one of the pipes is likely to be the vac feed to the tap.
Note also that if it IS a vacuum tap, you won't get any fuel out of it unless you present the feed with a vacuum - you should be able to see the vacuum feed pipe inlet on the tap - suck on this and the fuel should flow. However, I suspect that you may well have a "normal" tap, and the vac feed pipe coming from the carb is redundant.
Hope that helps (and hope it doesn't sound too patronising if you knew all that stuff!)
Cheers
