Hello everyone, Just been out for a little tootle - just a few miles - around the country lanes down here in sunny Devon ( hot, isn't it?!) Something which spoils the fun a bit is that when I stop, for example to make way for a vehicle coming the other way, instead of ticking over nicely the bike has a tendency to stall, unless I keep revving the engine. It's a 1965 B40F (side points.) Could someone talk me through what to do, in the order I should do it, to stop the stalling? Many thanks in advance. Please remember I don't know much about this! Phil
make sure its set to tick over on the slide stop and not being held on the cable .
What do you mean by held on the cable? Do you mean needing to use throttle?
So, first of all turn, the stop screw in a bit?
with the throttle closed have you any free length/slack in the cable ? there needs to be a small amount and tick over set on the slide stop .
Excuse my dimness, but should I be adjusting this at the twistgrip or at the throttle stop screw on the carb? Phil
tick over at the throttle stop screw and pilot mixture screw first
I think craigc11g means that it is possible to adjust the throttle cable for idle revs. The correct way is to have the cable adjusted so that the slide bottoms when you keeps your hand off the twist grip. Then you adjust idle with the slide stop. One reason is that idle can change when the wheel is pointing left or right.
In my experience it is common that you have to adjust idling as engine warms up.
Had to relocate the battery on my B40 to be able to do it on the Monobloc someone had fitted to it.
Before I read your post about the pilot screw, I went to the garage and turned the throttle stop screw on the carb clockwise half a turn. Started the bike. Very different. Brisk tickover. So turned it back a quarter of a turn. Still very different from before. Quite a brisk tickover, no sign of stalling. Do I know need to turn the pilot screw clockwise until the engine runs unevenly and then anticlockwise until it's running nicely ? Is that right? Phil
Ah, just seen Mike's post. So there are three things at play here: pilot screw, throttle stop screw, and cable adjuster? Phil
I vaguely remember doing something a while ago to stop revs increasing when I turned the handlebars. Phil
It's fairly easy. First a little slack in throttle cable when slide is bottomed. Warm up engine. Then set a good idle speed with the slide stop. Then adjust pilot screw until you get highest revs. Lower slide stop till decent idle. Check by changing pilot screw again. If revs go down whichever way you turn pilot screw, you're spot on.
"I vaguely remember doing something a while ago to stop revs increasing when I turned the handlebars. Phil"
If this happens you should look at the cable routing. It can be too tidy. This would fail an MOT if we still had to have them and is potentially very dangerous especially when manoeuvring in narrow country lanes and full lock may be needed.
Dave.
Top tips!
In addition to all the above, I get more consistent results for setting idle if I use 91 octane fuel with no ethanol.
Okay thanks everyone. I've screwed in the pilot screw until the engine ran unevenly, then out until similar, and found a position of max revs in-between. Then adjusted throttle stop screw for a steady tickover. The result is the screws are in the same positions as before, exept the throttle stop screw is a quarter of a turn further in. Even just that little bit makes a difference. Also there's no rise in revs when handlebars are turned. So hopefully that's it sorted, and my education has moved on another small step. And it's been fun of course. Thanks again. Phil
By the way, just in case you're interested, my carb is a Concentric 626. I think that probably wouldn't be what was originally on the bike (1965 B40F) when it rolled out of the factory. Maybe would have been a Monobloc? Phil
I think the bike was originally despatched to the MOD for the Auxiliary Fire Service, but don't imagine that would have made any difference to what carb was fitted at manufacture? Phil
I think the Monobloc was superseded by the Concentric in 1967. On the bikes I know about anyhow.
It's said that it improved fuel consumption, otherwise no big difference in performance. The slimmer Concentric made it easier to fit two side by side on twins.