FE390 engine spitting - need help

[Stephan427SC]

Hi guys,

I have a FE390 engine with 4 IDA webers and a MSD ignition controler. If I start the engine, it idles good, but on passenger side, you can hear a small spitting out of the pipe.

I measured the temperature on the header-tubes while running and found out, that cylinder 1,3 & 4 only had 60°C. On all other header-tubes the temperature rises very fast, but on those three the temperature stays at about 60°C. Other tubes warmed up on about 250°C very fast....

Ichecked the sparkplugs and they have spark.....

Any idea what can solve the problem ?

Best,

Stephan