Last race weekend I had 2 days of perfect running, then on day 3 the bike turned into a stalling, lurching, bucking bronco. Am looking for some thoughts about what to focus on... I lost a race weekend and a few podium finishes because of this.
RC51 SP2 with a built motor & tranny, CF snorkel & open airbox (seals against bottom of stock fuel tank), custom exhaust.
Please excuse the long-winded description below, I tried to give as much detail as possible.
Thanks in advance,
RACE Round-3 weekend
Fuel/electrical issues with GDRacing RC51
This was the first race weekend that I would be running race fuel in the RC51. I selected VP MR12, which I ran straight in the tank without dilution.
- The bike’s PowerCommander PC3usb had NOT been remapped for using race fuel.
- Was advised that it would probably not be necessary to remap for MR12, that it could likely be used with the existing map.
- Did not add pressure hose from CF airbox to fuel tank (using 1-way valve)
- OEM fuel tank with LighTech 1/4 turn fuel tank cap
- OEM in-tank fuel pump & filter assembly, OEM pressure regulator
- No heat shielding added to fuel tank.
Saturday (testing & qualifying)
- On Friday, July 22nd the weather was very hot & humid… approximately 33°C with high humidex.
- Ran straight MR12 in the bike all day, and it ran very strongly & consistently without any problems.
- The exhaust muffler core & outlet was a light grey/brown colour. Race fuel was stored outside, but in shade.
- At the end of the day, I pumped out the majority of the MR12 fuel from the bike’s fuel tank.
Sunday (testing & finals)
- On Saturday, July 23rd the weather was again very hot & humid… same or higher temperature than Friday with higher humidex.
- Again, ran straight MR12 in the bike all day, and it ran the same as Friday… very strong & consistently.
- At the end of the day, I did NOT pump out the bike’s fuel tank… I kept the MR12 in the fuel tank.
On Sunday, July 24th the weather was noticeably cooler than the previous 2 days… approximately 5-7°C cooler and not nearly as humid.
Was running the MR12 that had been left overnight in the bike’s fuel tank (4:30PM – 8:30AM : approximately 16hrs).
Morning practice session 1:
Morning practice session 2:
- Bike started well.
- After 2 laps the bike started lurching severely on & off power, and the FI light would flash intermittently. Had to come in because the bike was unrideable.
Morning practice session 3:
- Tried pumping out all the MR12 from the bike’s fuel tank (got a lot but not all)
- Put in 91 no-ethanol pump gas into the tank.
- Bike run fairly smoothly without large problems, but was down on power compared to race fuel.
- Tried pumping out 91 pump gas, and adding race fuel again (Fresh MR9 this time).
- Bike ran okay for 1 lap, then started hesitating again.
- Mid practice, the +ve battery wire broke off and left the bike without power.
- Did makeshift repair on the +ve battery wire, verified main & starter relay fuses were okay.
- Ran MR9 race fuel
- Warm-up lap the bike ran okay with some sporadic minor hesitations, but I was not pushing it
- Launch was okay.
- By end of 1st lap the bike was missing & hesitating a bit. By 2 corners later (high-speed, nearly full throttle) the bike was severely cutting out & bucking, with FI light flashing when this happened
- Pulled off, DNF
- Pumped out as much MR9 race fuel from bike’s fuel tank as I could, added 91 pump gas
- Warm-up lap the bike ran okay, not pushing it
- Launch was okay.
- By end of 1st lap the bike was starting to miss & hesitate again.
- Pulled off, DNF
I am confused why the bike ran so well for 2 days on MR12 but then encountered the problems it did on the third day. I was concerned that it might have been because I left the MR12 overnight in the fuel tank and it affected the tank, fuel pump, and filter (internal). However, many people have said that the short timeframe should not have caused those problems. Removing the race fuel & running pump gas seemed to work for a short time, but not completely solve the issues. Bike would run for first lap or 2 then would start acting up. Battery +ve wire needs to be repaired.