Hi, Helga is running loads better now I have the automatic choke issue sorted (thanks again for all the advice!!). Though she seems to be running at a high tickover. I have reduced the tickover screw on the carb but still running fast imo. This is on the top of the carb, I think it is a manual choke. https://photos.app.goo.gl/cdM1mNTmaX74Tn7R6 Might there need to be an adjustment here? It's not on the bottom step. If I move it to the bottom step manually the tickover is reduced to a healthier level!
Wait until the choke warms up and moves its shaft onto the very smallest step of the fast idle cam (the zigzag thing). Then set the idle speed.
Hi Snotty, she is already warm and the idle speed is the lowest it will go. By last step do you mean the lowest ( first) step or the longer area just before the first step? She will go to the first step but not the pre-step area. Cheers p.s. I changed the embed to a link so you can see the step.
That is the bottom step on the fast idle cam. But…how are you adjusting the idle? It’s not done with that screw. It’s done with the big idle screw on the side of the carb.
The step thing holds the throttle open a fair bit on all but the last step. So if the choke mechanism fails to rotate until the adjuster screw is not touching the stepped cam, you have to let it warm up as @Zed says, then rotate the choke heater capsule until the stepped cam drops right down when you blip the throttle so the adjustment screw is not locking the cam(with the screw resting on the stepped cam, the cam will not move) On the bottom step, screw not touching, that shuts off the main throttle sealing up the main venturi. (And blocking the vacuum to the distributor advance as well) Vacuum advance at idle is another reason for high idle. Now you can use the air volume screw and the mixture screw on the side to iteratively set the idle, change one then the other, homing in on best idle at 850 rpm, using what is actually a second small carburettor just for idling. My carburettor came to me in a state where the stepped cam would not drop down reliably even when the lever from the choke left loads of space. Somebody had hammered the bushing that the stepped cam rotates on, and it had bulged and it caused friction where there should be none.
"and then rotate the choke heater capsule"... Please can you tell me where this is? https://1drv.ms/u/s!AlMJmF3F7Vc-ktZK2yrU16TiSW9yiA this is the auto choke side, I can loosen the three screws and rotate the auto choke, but I dont want to do this. https://1drv.ms/u/s!AlMJmF3F7Vc-ktZJ9StoKSzF0AjMtw what do I need to loosen to rotate the heater capsule? Thanks in advance
Choke heater capsule is the autochoke.. and it is those three screws Sent from my SM-T580 using Tapatalk
Thanks for your reply, if I loosen the three screws and twist the auto choke the stepped cam on the other side of the choke does not rotate with it. What am I not understanding??
That's correct. You're just putting more or less tension in the bimetallic spring in the choke unit. If you look at your first pic, you can see three lines on the heater body and a pointer on the clamp as an aid to adjustment. Tweaking will make the choke come off fully sooner, or later, depending on tweakage.
You need to lift the arm clear of the stepped cam, it's sort of loose from the choke but has a weak spring to cause it to take up the slack when you use your throttle. Sorry for that bad explanation.
@Zed Do you mean this bit? https://1drv.ms/u/s!AlMJmF3F7Vc-ktZRHRFgjAoSaO4WGA?e=lYyHTG If so, the steps are: 1. loosen the three bolts 2. lift arm away from the stepped cam 3. move the stepped cam into the correct position 4. lower the arm 5. tighten the bolts Sorry for being a dufus - thanks for your advice - I owe you many beer!
Cold engine (and cold choke so ignition off for a while). Forget steps for a minute. Lift arm away then rotate the choke body clockwise. If you look in the top of the carb you'll see the choke plate which will be in closed position. Rotate the choke body until the choke plate starts to open. When it's about 1/4 way towards vertical i.e. still 3/4 closed stop and tighten the three bolts. That should result in the lever being on the bottom step when the engine is warmed and the choke has come right off (plate vertical). Explanation: the choke does two things. It blocks air flow causing a partial vacuum to suck more fuel through the jets. It also keeps tickover revs higher using the stepped cam.
I suggested setting at 3/4 closed because you don't need full choke in the UK. Once you get the choke coming fully off i.e. plate vertical and on bottom step when warmed up, you'll need to set the mix and speed with the two screws on the side. When you've done that you may find on cold start that the revs are too high i.e. the lever is on too high step. That shows you don't need even 3/4 choke so you might like to adjust that so the plate is hslf open when cold. Note that to set the choke"on" for a cold start you must press and release the accelerator pedal. This alows that spring I mentioned earlier to rotate the plate and stepped cam, free of the lever which would prevent it moving otherwise.
