Originally Posted by Lilja

So I have a Plus-4 BTT engine that Ive run around 1½ gallons and Im having some issues with it I gotta say. Ive ran OS in the past with no issues at all, but Im really struggling finding a tune on this engine.
The problem seems to be like. First of all it takes forever for it to heat up, I have to warm it up in the pits for like 5 minutes first and then drive an additional 3-4 laps before it stops bluddering on the straight.
After its heated up properly it runs but still feels like its running a bit rich, however, the temperature is good and feels like I cant really run it leaner cause itll get too hot.
So today I was fiddling with it alittle and decided to try and lean it alittle, what happend was that it randomly stalled 3 times within 2 tanks of fuel, just for no apparent reason but it ran much better and had much more power.
I richened it alittle again and changed the plug to a 7 instead of a 6, just to be able to drive. And it didnt stop but at the same time I drove almost 6-7 laps with it feeling rich on the straight, not super rich but you know, some what reduced powerwise.
After those 6-7 laps it started to run better while it got hotter until I ran out of fuel and decided enough for today.

Now Im hoping someone can shed some light on why its acting like that. Im not an expert at tuning engines, but normally I just have a hard time getting the idle right but the idle isnt the problem here, so it feels like its not a tuning issue but Im not ruling it out either.
I should also say that its been acting like this since it was new, so its not something thats suddenly appeared. Its always been difficult to find a good tune and always taken a really long time to heat up and always been feeling rich even if its been okay temperature wise.