Solex sidedrafts - High Idle!

[twenty6]

Hi there, have a bit of a problem with these sidedraft carbs, have researched a lot including heaps of threads here but haven't been able to find an answer.

I'm still learning about carbs so this have been quite a timely process.

The setup;

5k with twin 40mm Solex Sidedrafts (and some aftermarket cam) I don't know if much else is relevant? No vacuum advance, brake booster running vacuum from the carb manifold.

The story;

Had a pair of running solexs on the car, long story short one of them developed a crack then a hole around the underside grub screw holding the venturi.

Found another pair pretty much on the other side of the world and purchased them in the apparent condition of quite good and not needing a rebuild, just a tune.

I put my jets, air correctors and emulsion tubes from my old set into my new set just because I knew they ran and I can always sort that out with tuning later.

Another long story short, the stage i'm at now is the carbs are on the manifold, and when the car is turned on, the initial idle is 1000rpm. After 2 or so seconds it rises to 1300rpm roughly then another 2 or so seconds it will sit around 1800rpm before finally settling at 2000rpm.

I'm pretty sure the carbs are balanced with the linkage.. I would assume so because there is the period of a few seconds where the car does idle at 1000. The idle stop screw on the throttle linkage is COMPLETELY backed off not even touching, and the IDLE MIXTURE SCREWS don't do anything whether they are turned in or out, fully, seated, anything.. no change.

Pretty sure there's no leak with vacuum, or between the carbs and manifold and manifold and motor although I have no gauge.
Here is a pic of the carbs in question (never mind the rtv it's just temporary as these are coming off and on all the time for troubleshooting)



If you need any more info just ask - hopefully someone has some advice because i'm at a dead end

[Dazza]

It could be a problem with the choke assemblies on one or both of the carbys. When the choke is pulled on it should richen up your fuel mixture as well as raise your idle speed. Most chokes bring the idle speed up to about 2000 RPM when they are on so you could have a problem with the chokes coming on even though the levers are in the off position.

[twenty6]

Thanks for your reply, I'm thinking along the same lines..

When these chokes are pulled the revs drop right down, if they are pulled all the way the car stalls.

Here is what the choke plate looks like with the top off



At the moment those 'holes' are matching up with whatever is under them.. I was thinking maybe they should be the other way round so those holes are matching up only when the chokes are pulled...

I tried re assembling them so it was the other way around but the car would not start.

[Dazza]

Do you still have the old carbys there to compare the choke setup to. I am thinking that someone has put the return spring on backwards so that the choke is being pulled on by the spring instead of off. Try turning up your idle speed screws a bit and see if it runs with the choke levers pulled back the opposite way to what they were.

[Celica RA45]

did those solexes come with electric wire s for the start up circuit ,they look like the pollution 1s from the 18rgu motors ,and the choke does look likec its on but with out hearing it idle i couldnt say

[petergoudie]

Send me your email address. I have a small soft copy of a genuine Solex manual. It might or might not be of assistance but it does have info on twin choke carbs.

[twenty6]

Do you still have the old carbys there to compare the choke setup to. I am thinking that someone has put the return spring on backwards so that the choke is being pulled on by the spring instead of off. Try turning up your idle speed screws a bit and see if it runs with the choke levers pulled back the opposite way to what they were.

Yes I do although the chokes are a little bit different, can't get to them by just removing the top 4 screws, will take them apart and have a look though. Where is the return spring located? These chokes aren't hooked up to any cable by the way.

Will try turning my idle speed screw in and pull levers back but that doesn't seem like the best fix, and I don't know how I would keep the levers back? thanks for your reply.

did those solexes come with electric wire s for the start up circuit ,they look like the pollution 1s from the 18rgu motors ,and the choke does look likec its on but with out hearing it idle i couldnt say

No they didn't.. :s How would I describe the idle to you? And what do you mean by the choke does look like it's on? Thankyou

Send me your email address. I have a small soft copy of a genuine Solex manual. It might or might not be of assistance but it does have info on twin choke carbs.

[email protected]

thanks!!

[Celica RA45]

if the carbies are hissing on idle the choke is on might only be 1 going just pull the lever to the fire wall choke should be on if the hissing noise goes off then the choke disc is back to front
do 1 at a time

[twenty6]

if the carbies are hissing on idle the choke is on might only be 1 going just pull the lever to the fire wall choke should be on if the hissing noise goes off then the choke disc is back to front
do 1 at a time

YES! The carbies do hiss, I thought the induction sound was a shite load louder than the previous ones. I'm thinking we're on to something

Both choke plates are assembled in the same position and both levers are facing the firewall (as you can see from pic, and that carbs are mounted on RH side of engine bay)

can you explain that again? thankyou

[Celica RA45]

pull the choke towards the radiator 1 at a time till the hiss stops .with motor running of course

[twenty6]

Awesome will give that a go tomorrow. Seeing as they're both in the same position at the moment wouldn't that mean they should both be put in the other position, or would it be normal for one choke plate to be different than the other? As I said both of them put around the other way the motor won't start but I guess that could be the idle mixture screws wrong.

Will give it a go tomorrow though thanks

[twenty6]

Ok so..

Both carbs hiss, the one closest to the radiator does it more than the rear one.

I put the choke plate on the carb closest to the radiator opposite to what it is, so technically 'closed'

The car started and idled better but then still rose to 2000rpm ...

I put both the choke plates to 'closed' and the idle mixture screws were seated or near fully in and the car wouldn't start or would start but instantly stall.

I screwed out the idle mixture screws about 4 turns and the car starts and idles and well under 2000rpm but the idle is always moving in 400rpm ranges whether from 600-1000rpm or 1300rpm-1700rpm, it's pretty volitile and the carbs 'pop' a little bit.

Is there just two ways you can put the choke plate or is there many?

[Celica RA45]

if you still are having problems sounds like a vacuum leak start it up and put your hand over each carby mouth and see which 1 sucks the least might be sucking air in from the side
also is the booster connected to the inlet for the brakes and on the carbs are both vacuum lines that go to 1 disy blocked off and also pullution for the other carby blocked off as well

[twenty6]

Hey yeah I'm pretty sure there's no vacuum leak as I've had one before, will check anyway though.

What's the pollution pipe look like? or roughly located. Theres a long skinny bronze pipe facing up on one carb blocked off by a rubber hose and bolt don't know if the other 1 has one

[Celica RA45]

in your pic there is 2 1 on front carby ans also back carby
and have you balanced the carbies to each other as well on the center pull there should be a adjustable screw need carby balancer to help on this 1
also mixture screws from closed off you turn it out 4 half turns no further as the motor will run richer