Yesterday I finally got round to cleaning The Fire Bike and trailer following the Guzzi Festival. I’ve been away. I started the bike and put it back in the garage. It was then that I noticed that fuel was steadily flowing out of the vent hole on the left hand carburettor. I quickly switched the fuel off. It’s the lower of these two holes.
It hadn’t been doing this while I was at the Guzzi festival. I frequently leave the fuel tap on for days but won’t from now on! The whole tank would have drained!
The only reasons for the carb to flood like this that I know of are;
- For the float to have a hole in it so that fuel gets in, it sinks and the needle valve stays open.
- For the float to have stuck so that that valve is open.
- For the float height to be well off and to cause the same.
- For the needle valve to be worn or dirty so that it won’t seal.
I gave the carb a few sharp taps in the hope that it was just a stuck float but, no luck.
There was no choice but to pull the carburettor off to have a look. First I removed the left side battery cover and the air filter box. It’s held on with two screws from underneath and a nut and bolt holding it to the frame at the top.
I seem to remember that I’ll have to remove the battery to get it back in and fitted against the rubber air intake. This was the next thing to come off.
Disconnect the throttle cable by removing the carb top and unhitching the cable from the slide. You need to hold the top on the carb as you remove the screws so that the spring inside doesn’t force the top up at an angle and damage the threads.
Although the fuel had been off all night, quite a bit of fuel came out of the carb intake at this point. I suppose the float chamber was full to the level of the vent hole and, when I removed the float and needle, it came up like a fountain.
Next I removed the plunger for the starter jet (choke) and disconnected the choke cable from it.
The fuel line was disconnected and then I undid the clamp holding the carburettor to the intake manifold.
In the past I’ve been able to wriggle carbs off the manifold at this point. However, I couldn’t budge this one so had to undo the screws securing the inlet manifold and remove the lot as a lump. Then transferred the bits to the bench.
I used the fuel from the spill to clean the outside of the carb. Then removed the nut securing the float bowl and the bowl itself.
The carburettor looks corroded inside but serviceable.
I have a problem now. I can’t get the float spindle out as there is so little of it protruding.
This spindle has got to come out before I can make any assessment of the float or needle valve. The little that is there is also rounded so I can’t get anything to grip it.
As far as I can tell, the original type of floats are no longer available although there is an alternative which will do the job. I’ll probably have to cut the float off so that I can get hold of more of the spindle. I shall be pretty “cheesed off” if it then turns out the float was fine. All the same, I can’t see any alternative.
As is always the case when you do something like this, I have found other things that are wrong. The end of the starter (choke) plunger is worn and needs to be replaced.
and there should be an O-ring in this groove in its cover.
I haven’t removed any other parts yet but can see it has a 135 main jet when all my literature says it should be a larger 145 jet. Assuming the same is in the other carb, it might explain why the bike struggles at full throttle.