My 500F seems to have a lot of engine vibration. The engine has been completely rebuilt, good compression, runs well and seems to perform as well as I would expect for an unmodified 500cc (19 HP) power plant. The exhaust has cracked at the muffler and at the pipe just downstream from the rear flange. As I have little time on task with Fiats, is this a Fiat thing or should I look further.

I have just looked at a ballanced crank and flywheel set up and note that the fly wheel has large hole located opposite to the flywheel counterweight. Is the flywheel set up to counter weight the crank on this 360 degree vertical twin and could my flywheel be installed incorectly.

Hi,
Exhausts cracking on Fiat 500's is not abnormal- there is a correct procedure to tightening them to reduce stress on the pipes and manifold studs- many of the replacement exhausts don't fit very well and the best option is to heat the pipes with an oxy torch at the bends to relieve stress after it has been tightened down.
If you reweld the exhaust flange with the exhaust fitted up on the engine it should be fine- mine cracked about 5 years ago and has done 30,000km since rewelding without a problem.
In regards to balancing there is a balancing mark at Top dead centre which is a small drilled mark in the outer section of the flywheel.
To check in the car you can remove the starter motor, turn the engine to TDC on the timing marks and check with a light and mirror that the TDC mark is pointing upwards through the starter hole.
It is possible to fit the flywheel incorrectly as there is no locating dowel to ensure that it only goes one way.
Some vibration is normal on a 500- it can be worse if the pistons are not rebalanced to the same weight during an engine rebuild but is more likely due to incorect assembly. Really it is only a problem if the engine continually disassembles itself while you are driving along...

Great advice.
So the flywheel must be balanced with the shaft. The assembly mark must ensure correct azamuth assembly.

Brinky said:

I have just looked at a ballanced crank and flywheel set up and note that the fly wheel has large hole located opposite to the flywheel counterweight. Is the flywheel set up to counter weight the crank on this 360 degree vertical twin and could my flywheel be installed incorectly.

Click to expand...

hi, my flywheel is aftermarket light one, and has no marking on it...