I have a pict 3/4 carb on a 1584 twin port. Although the mixture screw appears to be working as prescribed, the bypass screw has limited affect on the idle speed. I can't get it to go much above 800rpm. I think I've got the fast idle screw about right on the cam, although its not easy. The choke is working, but could I have it at the wrong setting, somehow blocking the idle adjustment? A couple of weeks ago it adjusted nicely, so what could have changed?
Take the jet out completely and inspect it for damage, blockage etc. I had one that had snapped off inside once, no amount of turning did anything
Good point. Could be partially blocked. I had problems with it not idling at all at the weekend. Silly question, does the jet simply screw out with the bypass screw?
Has a rubber seal / o ring on check that’s ok and their , the jet can get damaged quite easily if you wind it in too hard as said take it out n have a look .
Solenoid clicks when pull wire on and off. Removed the Idle bypass screw, which looked fine and blew some GT85 (wd40 for bikes) down the hole to clear any muck. O-ring was a bit cracked and old looking, but not knackered. Put some grease around the O-ring and replaced it. Still cannot get the idle above 850rpm (lucky co-incidence?). I've ordered some more O-rings. Is it fair to assume this is the issue? Incidentally, mixture screw seems to work as prescribed.
Check the shutoff solenoid has the end on, they get chopped off sometimes, use the mixture screw to adjust the idle too, do you know if it’s running rich or lean, got an emissions tester?
I’ve had idling issues on and off for 14 years! In my experience cheap repro carbs are half the trouble. I changed mine to a rebuilt original carb and it’s been fine even since. Don’t forget to clean out the little pilot jet on the right hand side of the carb. I used to take everything out. Fill it with carb cleaner. Then jet it with the air hose.
Not got a tester. The van runs fine when fully warmed up, but struggles to idle when cold, unless its sat on the top step of the cam. Its been like this for a while. However, following last weekend's temporary refusal to idle at the end of a long run (presumably crap in there somewhere), it will idle when warm, but I can't adjust the idle, other than to kill it when I screw the bypass fully home. Could this suggest inadequate fuelling at idle? Maybe a blockage somewhere in the carb? I'll clean the pilot jet and report back. Thanks all.
Cleaning the pilot jet didn't work. Wonder if there could be a blockage restricting fuelling at idle somewhere else. Possibly the residue of the problem I had at the weekend? Incidentally, I replaced the fuel filter at the weekend as it had collected some bits from the tank.
Ironically, I was about to ask that question. Its a 1584cc 1979 van. How can I tell which model of carb. I have? I have one vacuum going to the SVDA and one blocked off in centre front, does this help?
If its a Solex it'll have something like Solex 34 PICT 3 cast into the side of it; on the float chamber I think. Bocar / Brosol copies normally the name and carb type stamped or cast in too. Edit: Here you go
