A friend (computerless) has a 300 Case that runs fine until it gets warmed up, then begins loosing power and sputtering. It worsens more quickly if it is under load. It did not do this until this year. He runs it without the sheetmetal and I suggested heshroud the carb & intake with sheetmetal in case it was freezing, since frost develops on the intake. He said it helped a little, but did not cure the condition. He has not rebuilt the carb, but cleaned it and all appears fine. When it runs it runs very smooth. Any help is appreciated. Let me know what information you need. I can also send pics, but the year is unknown. All I have are some numbers off the block which are 06-B17987. The serial number plate is missing.

Mine was doing the exact same thing the other night. Mine was dirt in the float valve in the carburetor. I had it apart and cleaned it twice before I got it right. The coil is also a possibility.

Thanks! I'll relay the information.

I've heard of condensors doing this when they get hot. Also, check the valve lash. If they are too tight that can cause missing when warm. LOL!

I was told that it is not a missing condition, rather more of a power loss or fade condition. He can let it sit for 20 minutes to clear up and can work it for another 20 minutes.