K4 misfire – carburetor overhaul

The K4 TL has suffered from a misfire – which was rather more pronounced at the end ofIMG_20150419_160359 last season in that it seemed to struggle to extend the ladder. We checked the ignition – there is a great spark exceeding 1/4″ from the electronic ignition. The vacuum advance unit looked suspect, so we removed that and cleaned it up. It isn’t very effective, but the engine seems to run fine as long as the timing is somewhere in the vicinity of just before TDC. As the engine misfires most as you open the throttle quickly.

So it was time to look at the carburetor. Perhaps one of the jets was blocked, or just some crud in the float bowl, or a sticking float needle.

So today I stripped it down, cleaned everything, and put it all back together. No significant difference. So I tried a road test, and it reached 40mph between Lowdham roundabout and the de-restriction sign – about 1/4 mile, which does not seem to bad at all, especially given a top speed of around 45mph. So all we can do is try it out for real, unless anyone has any other bright ideas how to improve things.

IMG_20150419_184534Finally, the throttle combination linkage, which combines the foot pedal with the ladder extend control, is rather worn. So do I bore out the links and manufacture a special oversize cotter pin, or do I fill the holes with silver solder, and re-bore then to the correct size?

About lowdhamstation

I am a director of a small (and very technical) business, a committed Christian, a Reader (and preacher) in my local village church, husband to my dear Frances, am interested in heritage railways, and heritage fire engines. I currently run a group that displays wartime and early post-war fire engines at 1940s re-enacting events and steam engine rallies. O yes, and vintage cars and motorbikes, and we live in a Victorian railway station.
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