Q. I have a 1999 Hayabusa with a hot start problem. It starts fine when cold and on choke, and also when hot if you start straight away after stopping, such as after fuelling up.
The problems start if it’s left for 20 minutes or so; the engine turns over fine but it will not start. I can smell fuel when cranking over. Sometimes the bike will restart after five minutes, at other times I have flattened the battery completely.
So far I have replaced the battery, plugs, and fuel filters, cleaned the injectors, checked crank and cam sensors and adjusted valve clearances, but it still has the same problem.
I would now assume it’s a fault on the fuel pump but once it starts there is no evidence of fuel starvation and the bike pulls strongly and cleanly as Busas do.
Ben Phillips, Portsmouth
A. If it’s been cranking over for a while, some fuel will pass through hence the smell, but it still sounds like a fuel pressure issue. The injector filters can get partially blocked over time and are probably due for cleaning/replacing. There’s also a filter in the fuel pump that should be checked.
Be careful when you reassemble the pump as there’s an O-ring that can get nipped by the pump body if it isn’t seated properly and lubricated beforehand. If that’s happened then there will be a loss of fuel pressure, too.