Hi,
Anyone who has any idea of any typical faults of a bad idling 1256 with Zenith 301Z carburettor.
First let me give you a background.
The engine is rebuilt with new carb, petrul pump, everything that sparks etc. The car has been driving beutiful since September until 3-4 day ago when I took it for a long drive and it started to go more and more bad. Just before I got home it sounded like the car was running on 3 cylinders only)
As I just had changed to a new carb I figured that that was the problem. My first assumption was that air was coming in somewhere on the foot of the carb so I opened and changed to new gaskets, but before I started the engine I opened the dizzy and found the the points didn't have enough gap so I adjusted them. After that the engine was going good with one exception. Going idle the rpm:s whent up and down and up and down.
My next step was to change the sparks and the ignition leads as at least the leads where NOS and I was anyway going to replace them. Still the same issue...
Now to be sure that the carb wasn't leaking any air I used starting gas around the foot and the cables but that didn't affect the RPM, but spraying into the airfilter made the RPM go up. So to me that was the proof that that wasnt the issue. (But still the engine didn't stop when tightening the air screw.)
Now my attention whent to the vacuum unit on the dizzy and I changed it to another one (used) but still the same issue. (Pulling off the small hose between the vacuum unit and the carb made the vacuum unit react and the engine stopped so it seems to be working though)
Just before writing this mail I have turned the dizzy in different directions to make sure that it didn't have anything about ithe gnition setting, but the rpm has gone up and down when turning it in any direction.
Now I need the forums knowledge of what that could be the next step.. I have some ideas myself that I havent tried.
1. Change to new points (They look fine though) My issue with this is that it might be hard to find in Sweden, but I will check tomorrow (I think the the dizzy is the same as on the Triumph spitfire mark 3 and 4)
2. Take of the airfilter and put my hand on top of the carb to make the petrol flow which might take away some dirt that might have gone in as there are no filter between the petrol pump and the carb. If that doesn't help take the apart and clean.
3. Adjust the valves (During the assemby of the engine I adjusted them but the motor was cold so they might need some small adjustments) This is hardly the issue but I'm starting loose options...
Any ideas?
/Christer