Thread: Rebuilt engine in and running - need help with the tuning

Thanks gents, for punting me in the right direction.

I thought I'd go back to basics, so I warmed the engine up.
Set the timing, with my thumb blocking the vacuum advance tube, by ear.
Seems to be smoothest about 4-5deg BTDC. Its 8:1 on 98 RON.
I also changed the plug and coil leads to my old TopGun ones (cause the other FML ones just dont feel right when you plug them on)

I then dialed in the low speed volume screw until its started to putt occasionally out of the exhaust, then dialled it out 1/4-1/2 a turn.

After that I checked all the bolts on the inlet manifold, the carb adaptor, and holding the carb to the adaptor, some were fairly lightly tightened down so I nipped them up. On the carb itself I gave the screws holding the emulsion plate to the float body a 1/4 turn, (at prob 5Nm) and tightened the 3 little screw on the cover for the economy diaphragm (they were really only finger tight, I tightened them sequentially to about 3-4Nm as well).

I checked the accelerator pump and linkage by pulling the inlet hose off the top of the carby and opening the throttle, you could hear the fuel coming in when the throttle was snapped open. I couldn't see any fuel, are you meant to do this test with the engine running or stationary? But the revs rose instantly.
There's no play in linkage at all, but I did notice on both my Zeniths the linkage is connected in the long throw position, which is supposedly for colder climates. Would that make any difference to throttle response?

Put the air filter back on and took it for a drive, a big, big improvement.
Its still a little hesitant if you come up to a junction in 2nd at walking pace, then accelerate to say half throttle, but overall drivability is pretty good. Its certainly not threatening to stall on acceleration like it was yesterday.
I also put into 3rd at walking pace and turned into a street with a reasonable incline and pressed down on the throttle, whilst it lugged it showed no signs of stalling or fuel starvation.

I think the crankshaft timing is OK as it seems to be running fine at wider throttle openings, although I've probably only done a maximum of 2kms on the road since firing it up for the first time.

Maybe I just need to take it for a decent drive to settle things down and see if that hesitancy goes as things free up. What do you think?

As I hate threads that don't have a conclusion...

Rather than keep trying to tinker, I thought I'd just fit the old carb on in place of the new one to either confirm or refute the new carb as the issue.

Popped the old one on, fired it up and hey presto, runs like a charm.

I'll strip the new one down and rebuild it at some point just for fun.

Does anyone know what the jet specs should be for a Zenith 361V, so I can check the carb is actually setup for the 2.25 engine?