FI, fuel & electrical issues - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 11 (permalink) Old 07-25-2011, 12:41 PM Thread Starter
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FI, fuel & electrical issues

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.
http://www.gdracing-canada.com/RC51.html


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


Preparation
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.

Notes:
  • 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.

Friday (practice)
  • On Friday, July 22nd the weather was very hot & humid… approximately 33C 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.


Saturday (testing & qualifying)
  • 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.

Sunday (testing & finals)
On Sunday, July 24th the weather was noticeably cooler than the previous 2 days… approximately 5-7C 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:
  • 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 2:
  • 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.

Morning practice session 3:
  • 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.

FINAL 1
  • 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

FINAL 2
  • 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

FINAL 3
  • Did not run final 3

FINAL THOUGHTS
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.

Last edited by GlennCauley; 07-25-2011 at 12:46 PM.
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post #2 of 11 (permalink) Old 07-25-2011, 03:11 PM Thread Starter
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Thinking this is an electrical issue. How would a bad rectifier/regulator/stator make the bike react? Would it make the bike's FI shut down?
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post #3 of 11 (permalink) Old 07-25-2011, 05:17 PM
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For the electrical issues, if the regulator/rectifier outright died, then you'd be running total loss which wouldn't last too long due to the electrical load demands.
Should be easy to see that with low voltage on the battery.
But that should be a permanent problem, not intermittent.

I'd rather the regulator die in that manner than the opposite, which is allowing over-voltage output. That will kill any and every electrical/electronic device on the bike.
Happened to a buddy's Suzuki. It trashed everything.

With the FI light flashing, it sounds more like a sporadic loss of power causing the ECU to cycle.
I'd double-check your electrical connections and grounds to ensure they're secure with no broken or pinched wires.

As a precaution, check your stator coil resistance and regulator output to see if they're out of spec.
Unfortunately, some bugs occur after the engine is at full temp and under race conditions (heat, vibration, etc.) that don't appear on the stands.
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post #4 of 11 (permalink) Old 07-25-2011, 08:40 PM
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Race fuel is really hard on Spark Plugs and your symptoms sound very similar to what would happen to my CBR when plugs were done. I was running C12 though and would store bike with full tank of fuel.
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post #5 of 11 (permalink) Old 07-26-2011, 09:38 AM Thread Starter
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We're thinking that the root cause is likely the broken main +ve wire at the battery. The metal tab broke where the wires are crimped/soldered. We tried stripping the 2 wires & jamming them against the battery terminal, and then clamping a plate over top to keep them in place.

We thought it would be okay, but it's looking like such was not the case.


Now looking for a +ve battery cable (with the inline fuse)... anyone? anyone?
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post #6 of 11 (permalink) Old 07-26-2011, 09:40 AM Thread Starter
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Pic of the weekend...
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post #7 of 11 (permalink) Old 07-26-2011, 10:42 AM
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Glenn,
At any point did you remove or mess with the fuel line going to the bottom of the tank/pump? The reason I ask is because a friend of mine had simliar symptoms at a track day event, and when he brought the bike to my shop we spent some time trying to diagnose the issue. It turned out he had removed the fuel tank and when he replaced it, he failed to properly locate the fuel line banjo fitting into the U shaped cradle that prevents it from rotating or moving. It moved and partially kinked the line resulting in hesitation and poor response from low to middle RPM ranges.
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post #8 of 11 (permalink) Old 07-26-2011, 11:23 AM Thread Starter
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We installed a CF open airbox before the season started, and had to reroute and reposition some of the fuel hosing. I had to raise the tank before this weekend to do some maintenance, but made sure no lines were pinched when I put it back into place. However, this would not really apply in this situation, as the bike had 2 full days of hard racing without any issues at all. It was only on the 3rd day that the problem started, with the electricals glitching and finally dying at one point due to the broken +ve battery cable. Regardless, I will be inspecting EVERYTHING so thank you for the reminder!
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post #9 of 11 (permalink) Old 07-26-2011, 11:44 AM Thread Starter
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post #10 of 11 (permalink) Old 07-26-2011, 12:20 PM
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I'd say some kind of fuel problem. replace the fuel filter and the spark plugs and try again. The filter is super easy to change, just pull out pump under the tank and replace filter. After removing fuel it should only take 30 minutes to take it out and replace the new. the last time I did this I left the old gasket and just put some form-a-gasket on it.
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