Silentblock wide bush engine mounts - limited space for carburettor

While I'm busy blogging I thought I'd share a picture of my engine mount and how it physically contacts both my Jetex 22mm carburettor and my fast flow fuel tap. There literally isn't any room to spare between them.

I've done over 1000km with this setup and my early concerns about whether engine movement might cause some problems have come to nothing. Of course the carb moves with the engine and its mounts, but the fuel tap obviously doesn't.

Jetex carburettor - sticking float

After fixing my inlet manifold gasket I stumbled into another problem. The engine wouldn't start, and then I noticed fuel flooding out of the carb onto the floor. The problem was an apparently commonplace sticking float. It wasn't sticking on the housing, but simply wasn't moving very freely on the pivot pin.

I considered removing the pin and float and sanding the float a little on the hinged faces, as per some ideas on the Lambretta forums. First of all though I though I'd get some WD40 into it and let it stand for a while. This did the trick - the float now falls freely under gravity and rises with the 'tide'.

Jetex carb air mixture screw

The setting for the Jetex air mixture screw is different to that of a Dell'orto, so don't blindly follow advice for the wrong carb. For a Dellorto SH carb we are told to start off about 1 ½ turns and go from there. For a Jetex however, there's a label on the side that clearly states we shouldn't be going more than ¾ turns out.

To set the mixture properly, first warm up your engine. Then set the throttle idle screw (no. 26 in the diagram above) so that it holds the throttle open with the engine slightly fast. Now we need to set the mixture screw (no. 13) so that the engine is smooth and regular. Turning the screw in will make the mixture leaner, and out will richen it. When you have the smoothest tickover try opening the throttle. If the engine splutters or stops then a little more adjustment, probably to make it richer, is needed to eliminate this.

You'll probably end up somewhere between ½ and ¾ turns out.