Air lever/ choke

[hoogerbooger]

Just about to fit one to my B40 with Concentric carb.looks like the lever I have works in the opposite direction to the original, with full cable pull being forward.

Can I just check that the full choke/ closed position for start-up is minimum cable pull ?

And no choke when engine warm is full cable pull ( so fully forward in my case)

[iansoady]

Sounds as though you have a magneto advance/retard lever which is normally fitted on the LHS of the bars. You could fit it there to get the "correct" operation or buy the correct one. I'd do the former being a cheapskate.

[hoogerbooger]

Bought it years ago as a choke lever...but too bird brained to double check  it was correct.....until now.

If I can get the cable run to work, then I don't suppose it matters which side it goes on. So which ever seems easiest to operate on the move.

So: fully cable pull is when warm?

[iansoady]

Yes.

[hoogerbooger]

looks a bit weird when air slide in...is this right. seems to stick out a long way. I guess once top screwed down the air slide spring is compressed so air slide is at bottom ( choke full on).......but now wondering if it won't rise enough and get to full open.

Also has made throttle much stiffer to turn.

(I'll recheck the part number and cable measurements....but not keen to undo as found it one hell of a faff getting both cables on and needle in)

[hoogerbooger]

Ah. Just done the obvious!! and taken the air filter off to look. slide fully open from about 1/3 of lever travel....

So sounds like I need to ignore handbook guidance of moving choke lever to half of travel once engine has started ........ maybe I need to mark up 1/6 of travel and 1/3 so I know the bit I feather back through as it warms up

[iansoady]

The guidance in the handbook is exactly that and shouldn't be taken as gospel. Every bike has its own foibles - just use feel and sound to get the right settings. It's worth remembering that on anything other than fully closed, the air slide has little effect at small throttle openings as it's within the throttle slide.

[rhyatt]

some of my bikes need choke , others a healthy tickle - as the air temp warms up, you will discover that you need less of this and more of that.
the joys of older bikes !!

[hoogerbooger]

Well, started it up and it's certainly not right. Engine ran like the clappers from the off, even when choke full off. So turned it off after 30 secs or so.

Not with it to investigate currently, but only thing I can think of is maybe I was a dullard and the butterfly is half way up the spring?.....as when I whipped the air filter of I coukd see the slides seem to be working ok.


( Am trying a choke, as was having to let it warm up quote a bit before riding to avoid it cutting out at the first couple of junctions)

[hoogerbooger]

(I had Vasalined the cork to get the Ewarts tap back in.....wonder if that enriched it??)

[V500]

Not to that extent!
Sounds like the slide is hanging.

[DAVE BRADY]

Hi,

The tap should have no affect unless it is restricting fuel supply. It sounds like the slide and perhaps the needle are not locating properly
The simple thing to do is recheck that the slide is returning to the bottom completely and is not being held up a bit by the choke. The slide should close quite quickly so check the feel and sound as you close the twist grip.
When refitting the slide complete with choke ensure that everything goes in the right place. If the needle snags on the side of the jet it can end up being pushed out of its clip.
Also recheck the other adjustment screws incase the slide is being held up too much.

Dave. 

[hoogerbooger]

Will do on Mon.

Both slides seem to function correctly when I checked after I switched off.

Getting the throttle slide in with the needle aligned is easier with the tank off.....but even that was giving me grief going back on this time !!

[hoogerbooger]

Seems to be working OK now. Not 100% sure of cause or if it might happen again.

Both slides moved freely when fitted in carb or out of carb. But main slide wasn't bottoming ( as picci shows) Needle/butterfly seated fine.

I adjusted the air slide so it just touched the bottom when cable fully slack, but that made no difference. Was head scratching with carb in hand and cap open and I decided inner cable must be caught up somewhere. Twisted the throttle grip a few times....no change. Cable outer seemed seated ok at both ends.For the sake of thoroughness ( desperation)I jiggled the cables up and down and stuck the slide back in....and it bottomed. So can only conclude the cable head had got a bit wedged in the wrong place with the twist grip......but leaves me a tad un-nerved.

( then carb wouldn't blooming tickle !! so had to remove again and strip/check. working now but not sure what was issue. May be disintegrating cork on the tap playing silly intermittent %uggers. Will see)

Any way. So choke fitted, but didn't seem to help at start up, in trying to hold it on an idle whilst it warmed up. Still had to hold the throttle open a tad. I haven't changed the pilot air setting from when it was last used in October ish. I had set it to a low tick over when fully warm...and hoped the choke would allow a low idle straight from kick-off, at all temperatures. Can turn the cable adjuster on the carb main slide....but won't that also raise the idle when it's warmed up ?

[DAVE BRADY]

Hi,

In my experience, even with a choke, a slow idle straight away from cold is not realistic.
A little bit of throttle will be needed even if only for 30secs or so.
How slow is your idle set to?

Dave.