After riding monobloc (& pre-monobloc) carbed bikes since the mid-sixties, thought I knew a fair bit about them. But apparently not...
Yesterday, after a fortnight's lack of enthusiasm following the 'flu I decided to get in the workshop and investigate the pilot jet on my GF. The bike runs perfectly well, but only with the air jet almost closed, so was curious as to why.
The ski-slope makes getting the pilot jet out in situ almost impossible, so I took the carb (monobloc) off and the jet out. Cleaned jet by rotating a wire cut from a wire brush and slightly bent inside the jet (my usual method) and blew through the carb with the airline. Refitted carb (set air screw to 1 1/2 turns out) tickled and started her up. Ran for two seconds and cut out. Wouldn't re-start so tickled again. Started and cut out completely after 2 seconds. Opening the throttle more made no difference until it was at least half open (with corresponding highly-revving engine). Closed air screw to just under 1/4 turn open, started - and it ran perfectly.
So for 60yrs I believed the pilot jet ceased to have much (any) effect above 1/8 - 1/4 throttle opening. Here I found it has a profound effect up to 1/2 throttle. The slide is correct at No3 and not badly worn. Haven't checked fuel level, but not sure that affects the pilot as much as the spray tube. BTW, the pilot is No 30 - apparently the largest available for those carbs, when I was fully expecting to find it to be too small at, say, 20.
Set at just under 1/4 turn open the bike idles and runs fine. Am not looking for things to do (I have enough jobs awaiting my attention) so will just enjoy riding it as is.
