Technical 903cc RPM
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Technical
903cc RPM
Ah, ok, it's the camshaft timing that I've been refering to. If the timing chain is worn it can jump a tooth and put the cam timing out a bit and give you the symptoms you've been experiencing.
To check it properly you would need to remove the timing chain cover, then you can see if the timing marks on the sprockets line up correctly. This is not a five minute job, but as everything else has been ruled out you may need to bite the bullet. Do you have a workshop manual that covers this engine? If you do just follow the section which covers timing chain and sprocket replacement. If you don't have a manual I can put the info on here for you.
Yep, not much wrong with that, bugger! Back to the drawing board.
Got the poping and missing under control but still no power.
I took it round the block and every quarter mile or so I stopped and adjusted the timing in tiny increments and it went from missing and rough running (too far advanced) through sounding ok but no power to missing and rough running (too far retarded).
I then tried the fuel adjustment screw and if fully closed the engine stalls but even a slight turn out and the engine runs but from then on it's the same, even if you remove the screw completely!.
In fact I'm not sure that screw does anything at all.
I took it round the block and every quarter mile or so I stopped and adjusted the timing in tiny increments and it went from missing and rough running (too far advanced) through sounding ok but no power to missing and rough running (too far retarded).
I then tried the fuel adjustment screw and if fully closed the engine stalls but even a slight turn out and the engine runs but from then on it's the same, even if you remove the screw completely!.
In fact I'm not sure that screw does anything at all.
No ideas that haven't already been said I'm afraid but if you need a 903 engine i broke an Autobianchi a112 a while back (shame but too rusty to save!) and I'm thinking about selling it so let me know if you give up on your engine!
Ant
Ant
spannerdude
Member
As a73uk said. Check the accelerator pump diaphragm.
spannerdude
Member
Does the A112 engine rotate anticlockwise?
Last edited:
58FIAT600
New member
Since you ruled out cam timing and compression only three things needed, fuel, air and spark.
Fuel and Air: It starts so we know fuel is OK at idle. You say it looses power is this only under load or does the car rev OK when stationary ? Since you tried another carb and got the same results, did you set the other carb up the same giving the same issue or did you leave it the way it came ? If it is not the carb are you getting enough fuel pressure ?
Spark: You swaped the points and condensor but I would still not rule either out, I hav seen multiple bad ones before. Are the HT leads OK ? If you ground a spark plug to the engine for each cylinder are all 4 sparks good ? and lastly but best guess for the root cause of your issue would be the vaccum advance, is it working correctly when you rev the engine ? does the timing mark move when viewed with a strobe on the belt ?
Good Luck, don't give up. It worked once, therefore it can run again.
Fuel and Air: It starts so we know fuel is OK at idle. You say it looses power is this only under load or does the car rev OK when stationary ? Since you tried another carb and got the same results, did you set the other carb up the same giving the same issue or did you leave it the way it came ? If it is not the carb are you getting enough fuel pressure ?
Spark: You swaped the points and condensor but I would still not rule either out, I hav seen multiple bad ones before. Are the HT leads OK ? If you ground a spark plug to the engine for each cylinder are all 4 sparks good ? and lastly but best guess for the root cause of your issue would be the vaccum advance, is it working correctly when you rev the engine ? does the timing mark move when viewed with a strobe on the belt ?
Good Luck, don't give up. It worked once, therefore it can run again.
It rotates clockwise sorry are you after anti-clockwise?
Sorry for the late reply!
Sorry for the late reply!
124spiderman
Member
The engine runs anti-clockwise, so be sure your timing is set at 10deg BTDC.
I've came across an 850s with timing out by 20deg!!!! The mechanic thought it ran conventional clockwise like most motors and set the timing accordingly. Result, no revs, spitting overheating and genrally running like cr*p. I'm amazed it even started up...albeit took some cranking effort though.........
I've came across an 850s with timing out by 20deg!!!! The mechanic thought it ran conventional clockwise like most motors and set the timing accordingly. Result, no revs, spitting overheating and genrally running like cr*p. I'm amazed it even started up...albeit took some cranking effort though.........