bigt

Kayla. Thanks for your help. I have tried lots of things over the past 2/3 weeks. I realised the problem was definatley carburation, and stripped, checked and cleaned everything, rebuilt it and no change! I have eventually found if I remove the large diameter pipe from the CV carb it runs OK! Have you or anyone else got any idea why this happens? Bigt

Bike is an SZR660 Yamaha. The engine is an XT660 single with the twin carb setup. It's in good condition and low mileage, about 8K miles. It's been stood for at least 6 months with fuel in it, I think. The problem is it won't rev at all. It's OK up to 3000 rpm but if I open the throttle too wide it just won't pull, it dies. It starts and ticks over lovely and sounds ace, nice and quiet. I've tried the following :- - stripped and cleaned the carbs, although there was no dirt or gunge to be seen - took the fuel tap off and drained the tank - put fresh fuel in - new spark plug - ran it without the air filter - removed the vacuum part of the fuel tap and run with straight through fuel supply. None of these have made any difference. My best guess is it's a fueling problem but can't find anything obvious. I had expected the main carb (CV?) to be the problem. The diaphragm appears to be in good condition. HELP!