Howdy, I have a 1971 Fiat 500 that has the 650 engine in it. Recently I rebuilt it with the help of some friends. My problem is it won't idle right. When I keep on the gas it runs and sounds fine. The moment I left off, it dies. Can someone give me some pointers on this. It is my first Fiat and I want to get it running right.
Thanks in advance, Robert

Hi Daswaf, some of the guy on here are good but you may still be better posting in the 500 classic section. As for me I'm clueless on it . Hope you get it sorted!

wrong forum mate

https://www.fiatforum.com/500-classic/

daswaf said:

Howdy, I have a 1971 Fiat 500 that has the 650 engine in it. Recently I rebuilt it with the help of some friends. My problem is it won't idle right. When I keep on the gas it runs and sounds fine. The moment I left off, it dies. Can someone give me some pointers on this. It is my first Fiat and I want to get it running right.
Thanks in advance, Robert

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As stated, the classic forum is the way to go but, as the question has been asked my first thoughts would be either a blocked idle jet in the carburretor or possibly too high a float level causing flooding as it is fine when main jet is in use.

There is the possibility it is running too rich but you will need to clean carb first and then ask re default setting of mixture screw (how many turns out from fully screwed in) before fine tuning.

All the above assumes that when you rebuilt it everything else what done correctly (valve timing, valve clearances, ignition etc.) and that you are also using the carb from a 650 engine, not the original 500 one,

Hi, check for air leaks in between the carb and base plate also have a tweak of the air/fuel mix screw. As you look at the carb on the engine, theres a screw towards the bottom on the right, fire up the engine, tweak this screw till it idles If its not that...............................er...........................

Panda van, is definitely right, there is an idles screw for the carb. All you need is too adjust it, its probably alittle too high.

i had a 650 years ago and the thing wouldnt start or ran rough, a fiat specialist told me the tappets were in need of adjustment, he did this and all was fine .
seems its crucial to have them spot on, hope this helps
steve

daswaf said:

Howdy, I have a 1971 Fiat 500 that has the 650 engine in it. Recently I rebuilt it with the help of some friends. My problem is it won't idle right. When I keep on the gas it runs and sounds fine. The moment I left off, it dies. Can someone give me some pointers on this. It is my first Fiat and I want to get it running right.
Thanks in advance, Robert

Click to expand...

Its usually play in the throttle spindle letting unmetered air into the carb, because the bushes are worn.
new carb or a rebiuld.