Had the exact same issues today with my 3 port R as the guy described below. Two very experienced tuners got it running amazingly. Let it sit for about an hour (no change in outside temp during this time) and it suddenly has about 65% top end speed and very erratic behavior. What could it be that is making it lose its tune like this? Air leaks, the carb? I'm still very new at this, but the people at my track are not and its even got them stumped.
Originally Posted by
Semple
Was at an open practice today. I had probably 5 really experienced guys trying to help me tune my 3 port R.
I fouled two O.S. P7's and one P3.
We tuned it rich, we tuned it lean, we tuned it just right. It wouldn't hold the tune over the course of a tank. I'd pull it in and park it on the box and go do my marshalling. Come back and it'd need to be re-tuned. It takes forever for the bottom end to load up, as well. We'd tune it rich, warm it up for several minutes, then throw it on the track. A few laps into it the throttle would do weird things. Kind of like a wobbling sound. Everyone said lean bog, so we'd be richening it to the point that the motor would almost choke up and flame out but it still happened. It also fouled 3 plugs as stated earlier. Fouled them at all different fuel:air mixtures.
Temps were around 175 all day.
What in this motor is causing tuning wonkiness and fouled plugs? $35 dollars worth of plugs adds up really fast.