Better performance witha full tank??? ideas

Just wondering if anyone has any ideas on why my 90 accelerates faster when with a full tank of fuel and why the performance steadily drops as the fuel gets lower and lower until the point where it nearly stalls when pulling away when the tank is nearly empty. had a new tank fitted less than a year ago so shouldnt b any crud in the bottom of the tank causing the problem. any ideas greatly appreciated.

Hole in fuel pickup high up letting in loads of air?

Checked yer filter lately... might just be crap from the tanks at the garage getting in or crap fuel?

lazy fuel lift pump?

Mine was doing this, and after some help here, found the fuel breather in the cap was blocked, and hence creating loads of positive pressure in the tank, which was affecting the flow of fuel back from the engine, and disturbing the fuel flow completly.

The main symptom was a huge wooosh of air when i removed the fuel filler.

just discoverd it has a fuel leak wher the filler pipe enters the tank. probably letting too much air in.

any particular way of unblocking the fuel cap breather?

bigwill said:

any particular way of unblocking the fuel cap breather?

Click to expand...

This do ye...

http://www.landyzone.co.uk/lz/f41/fuel-cap-72130.html

08mckerp said:

just discoverd it has a fuel leak wher the filler pipe enters the tank. probably letting too much air in.

Click to expand...

It can't let too much air in. More likely a pinhole somewhere in the lift pipe.