Hi Tony,
I haven't ran the .28 yet in my MBX5T so I can't comment on run times for it.
But in my MBX5T I ran the .21 Ninja with both the Ninja 2053 pipe and long Ninja header and then I tried the MSR1005 pipe & header. I could get 12 minutes run time with the Ninja pipe and 11 to 11-1/2 minutes with the MSR pipe. That was with the plug inside the tank removed and a long Mugen fuel filter.
I run 30% Maxy's fuel, Ninja #6 plug, stock 7mm venturi and added one thin copper shim (0.004") to increase the deck height. LSN = 5.5 turns out, HSN = 4 turns out. When looking at the needles both are at the 1 o'clock position.
When you set up your throttle EPA, remove the air cleaner and watch the carb open. Limit the EPA to where the carb is fully open to the 7mm restrictor. The carb will open about another millimeter, but it is a waste. Once the EPA is set, re-install the air cleaner and make note of the EPA setting on your radio. Re-adjust if you ever move the motor or linkages around. Also make sure the clutch is working properly. an improperly tuned clutch can cost you lots of run time. I run the Mugen standard alum shoes with 1.0 spring setup on my Mugen flywheel with Mugen clutch bell. Overall gearing is stock at 16.28:1. I don't tune to a temp gun but anytime someone temped my motor it was always in that 230-250* range.
Hope that helps.
Last edited by TonysScrews; 05-14-2007 at 07:00 PM.