Technical Adjusting carb and throttle-cable

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Technical Adjusting carb and throttle-cable

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I've been digging deep and finding some specialist websites:eek:....no, not that type; ones about Weber carbs.
We all know that the engine tickover needs to be fairly slow when adjusting the mixture, but I read somewhere, on a much more sophisticated carb, that the throttle butterfly should be adjusted so that it is barely open; ie. the screw is just touching the stop. This is to avoid exposing any of the tiny progression holes, which would affect the mixture adjustment.
I don't think that's possible on the 26IMB but using that principle and having first got the timing spot-on, I adjusted the mixture the usual way after achieving a really minimal tickover and found it much more obvious when I had achieved that "sweet spot".
Subsequently also found that it was much easier to get a steady, but fairly slow idle. I know that there are advantages in having a fairly fast idle, but I think that upwards gearchanging with the non-synchro gearbox is easier when the tickover is slow.
A useful discovery that came out of this is that when the tickover has been slowed down, it creates a slight amount of slack in the throttle cable. If not adjusted you may not be able to achieve maximum throttle opening. The situation is simulated in the photo.
MAL_1785 by Peter Thompson, on Flickr
 
One of the things I always do when installing any carburetor is to test that the throttle plate opens full to the max open stop with the pedal pushed all the way to the floor, and that the throttle plate also returns completely closed with the idle speed screw backed off.
With the standard Weber carb on these cars I also do the same for the fuel enrichment piston (choke). Make sure it goes full on and off.
Sounds like you are really dialing your car in Peter!
John
 
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Sounds like you are really dialing your car in Peter!
John

Since I got those spotlamps on my birthday exactly one month ago, I must have spent, on average, at least two hours a day tweaking and experimenting with various things to further improve reliability and performance. I've also been tying-up any "loose-ends" that have escaped being sorted, such as temperamental windscreen-washers, dodgy licence-plate light and rusting wheel-rims.
I had an intention to eventually develop the other decrepit shell of a 500 that I own into a super-rugged, ultra-reliable, world-travelling, mile-muncher, but it looks like Murf has a chance of accidentally evolving that way.:)
 
Ehmmm interesting. I have always found a slightly high tickover to be better for me on the old points and condenser setup. I don't know if the advance weights and springs are showing their age on my old dizzy? I suspect they are. I always found that if I set it too low with the old setup, then when I was driving and come to a stop at a junction etc, the revs would drop at idle and it would putt, putt a few times before he returned to a decent idle.

With the 123 it purrs like a kitten after about 30 seconds. My method of starting is usually give it loads of fuel enrichment (choke) to start with but knock it off to virtually nothing once it has started, so within the first 10 seconds. Then take it right off. Then a little hand throttle for about 20 seconds to raise the revs and get it warmed up, then take that off. Then Luigi purrs like a contented kitten at really low revs and doesn't miss a beat. I don't get any of the issues with revs dropping at junctions anymore, which must have been down to the old distributor?
 
Then a little hand throttle for about 20 seconds to raise the revs and get it warmed up, then take that off.
I must reconnect my hand-throttle now that I understand the real use and importance of it.
Upate to the throttle adjustment....it also makes driving more fun with a slower tickover because it improves engine braking, which makes handling better; the knock-on effect is also that it causes less strain on the brakes because they are not fighting such a strong force from the engine.
 
The much overlooked hand throttle also can be of great use if you are out on a run and you hit a problem or something goes a little out of tune. If you tweet it on you can avoid that horrible stalling at road junctions etc. I have used it as a "get you home" device
 
The much overlooked hand throttle also can be of great use if you are out on a run and you hit a problem or something goes a little out of tune. If you tweet it on you can avoid that horrible stalling at road junctions etc. I have used it as a "get you home" device

I used a pair of mole grips as a "get you home" device once when the accelerator cable snapped. Connected them up to the remainder of the cable near the handbrake and used it as a handle throttle.:D
 
My acceratotor cable snapped. I had just got on to the M1 giving it some beans & heading north from London. I managed to connect the stub to the linkage but I guess the engine was running at a minimum of 2500rpm with a sport exhaust. I got off the motorway at Watford and into the lanes I know well. On a single track lane I rounded a corner and two horse riders were coming the other way. Fortunately the horses did not freak out with the noise and passed by safely, not sure what the riders thought !
A few weeks later on a similar journey my clutch cable broke. I was still rolling so my brain went into overdrive to work out if I could possibly drive home without a clutch and the best route. Somehow I managed to make it from the north circular all the way to Rickmansworth where there was a local classic car meet that day at the Aquadrome. I made it into the narrow drive and got to the gate. The guy on the gate seeing a classic opened the gate and smiled as I approached. I shouted through the open sunroof "sorry mate , can't stop I have no clutch" . I drove down and round the field for the meeting looking for any source of help but it was still quite early Sunday morning so I drove back out of the Aquadrome heading for Chesham. So many heart in the mouth moments at roundabouts and traffic lights but the traffic queue over junction 18 Chorleywood was just too much and I managed to swing into a side road. Turned out my 100,000 mile plus clutch pedal and cable were so worn it had dropped out. Did a bit of a bodge with the emergency kit and made it the next six miles home :)
 
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