m-38 putt-putt-putt at idle speed

1948willyman · Post by **1948willyman** » Sat Oct 04, 2014 12:02 pm

Engine runs fine up the road with no issues . It pulls under load up a hill fine with no miss. But it has a distinct spit and putt at idle I do not like. Guess a little too particular about the idle which I would like for it to puurrr a little more
smoothly.Carb was rebuilt due to diaphragm problem but was doing this before anyway. Engine Compression fine with new wires and plugs Anyone have any ideas what may be causing this or is this just typical of these engines. Didn't know if the ignition points or coil or timing could cause this type of problem as it has a new dist. cap also

Post by **wesk** » Sat Oct 04, 2014 12:33 pm

The L and F 134's have a very distinctive idle pop that is quite normal. If the engine shows no issues in use then there are no issues. An increase in the oddity of the noise occurs when the tail pipe ends up aimed at the inside of the right rear bumperette.

Mjfire1949 · Post by **Mjfire1949** » Sat Oct 04, 2014 6:25 pm

My M-38 does the same thing. It runs too good for me to worry about it though. I did replace the exhaust system. The ""putt-putt" noise now exits out the rear rather than under the tub from a rusty tailpipe. I don't even notice it now.

oilleaker1 · Post by **oilleaker1** » Sun Oct 05, 2014 6:25 am

I've reduced the put put on mine by adjusting the idle mixture and setting valve clearances. If they get a little tight on the valves, they put put more. If they have a bad valve, they put put constantly at a idle. John

Post by **wesk** » Sun Oct 05, 2014 9:05 am

Just to be sure John isn't misleading you :

If they have a bad valve, they put put constantly at a idle.

If they have very good valves they will still have the put-put at idle. As I said above, if the engine has no performance problems then most likely you are suffering from the basic put-put which is the nature of the beast. If you wish to try to reduce the put-put then by all means do the following even though the engine's current performance is fine:

1-Compression checks and leak down test.
2-Check timing and point gap.
3-Clean, test & gap plugs.
4-Check carb float setting, idle mixture setting and vac diaphragms.
5-Check tail pipe position.
6-I caution against setting valves to other then the correct spec just to reduce put-put at idle.