Sudden Lean Condition

Discussion in 'EFI/carb' started by Suputin, Aug 10, 2014.

  1. Suputin Husqvarna
    AA Class

    Husqvarna Motorcycle:
    2011 SMR 511
    Other Motorcycles:
    WR250X, 81 Yamaha RD350LC, 90 RZ350
    The ECU on my 511 has been reflashed by Zip Tye and it generally runs a teeny bit rich. The other day I got on the bike and within the first couple of kilometres it did something it has never done before, popped on deceleration. Then once I hit the highway the bike began to surge and generally run badly on constant throttle.

    Thankfully I have an AF mixture gauge installed and the gauge instantly showed the problem. The motor was running quite lean. Normal running should be in the high 12's to low 13's. This time I was seeing 15's and 16's. Interestingly the engine was lean at every throttle position except WFO where it dropped back into the 13's.

    So I brought the bike home and saved the engine. At this point the $200 investment in the AF mixture gauge has saved an extremely expensive engine rebuild.

    Anyone got any ideas as to why a well running 511 SMR might suddenly go very lean?

    The only thing I have heard of is potentially a cracked intake boot. Sadly, getting at the throttle body is gonna be a PIA but it is all I have at the moment.
    Big Timmy likes this.
  2. Dangermouse449 Husqvarna
    Pro Class

    Location:
    Sunshine Coast QLD Australia
    Husqvarna Motorcycle:
    2011 TE449
    Other Motorcycles:
    2009 CRF450R 2000 YZ125
    The clamps on my throttle body were fairly loose at one stage. Something to check.
    If you do suspect the boot (only the one below the butterfly could make it run badly), try having the bike idling & lightly spray some carb cleaner on the rubber joiner & see if the revs change.

    It is possible that one of the temp sensors (fuel/coolant) is playing up & affecting the fuelling....
    Big Timmy likes this.
  3. PawPaw Husqvarna
    AA Class

    Husqvarna Motorcycle:
    2013 TC 449
    Other Motorcycles:
    Honda Crf450R + old CB750
    The TPS can cause this issue as well. The TPC regulates the fuel mix based on the throttle opening. The max opening will give the richest mixture. Check the TPS wires to be sure the unit is not unplugged or the unit is not bad. The TPS is also adjustable to make you run richer or leaner.

    Paw Paw
  4. Dangermouse449 Husqvarna
    Pro Class

    Location:
    Sunshine Coast QLD Australia
    Husqvarna Motorcycle:
    2011 TE449
    Other Motorcycles:
    2009 CRF450R 2000 YZ125
    There's some base figures here, but yours shouldn't have changed unless the sensor has gone bad or been undone.
    As Paw Paw has said, if the wiring has come loose for the PCV it may not be running....

    http://www.cafehusky.com/threads/449-511-manually-setting-tps-using-test-leads.43940/#post-426607
  5. Suputin Husqvarna
    AA Class

    Husqvarna Motorcycle:
    2011 SMR 511
    Other Motorcycles:
    WR250X, 81 Yamaha RD350LC, 90 RZ350

    Uh oh! I think this might be the issue. My buddy has a KTM and wanted to see if the TPS on his bike was the same as mine. He unplugged my TPS to compare it to his. I assumed he had plugged it back in and never checked it.

    I haven't pulled anything apart yet so this will be the first thing I check. It would certainly explain why the sudden change from running perfectly to running like shite.
  6. Dangermouse449 Husqvarna
    Pro Class

    Location:
    Sunshine Coast QLD Australia
    Husqvarna Motorcycle:
    2011 TE449
    Other Motorcycles:
    2009 CRF450R 2000 YZ125

    If it has been off the bike, you'll need to set it up again, the mounting hole is slotted to slide it back & forth, small movements make large changes.
    Use the TPS reading on the PCV to reset it to the correct voltage 0.7v.

    If it has just been unplugged, as long as the power wasn't turned on, you should be sweet.
    If it was run unplugged there is a possibility of causing damage, but should be ok,

    Also, just to confirm, it was your lower primary TPS sensor he fiddled with, not the upper secondary TPS near the square throttle motor cover???
  7. Suputin Husqvarna
    AA Class

    Husqvarna Motorcycle:
    2011 SMR 511
    Other Motorcycles:
    WR250X, 81 Yamaha RD350LC, 90 RZ350

    The TPS was not removed, just unplugged to compare the connectors. The engine ran for about 10 kms like that so hopefully it hasn't damaged the TPS. I wasn't aware there were two TPS. This is the one with that is adjustable FWIW.
  8. Dangermouse449 Husqvarna
    Pro Class

    Location:
    Sunshine Coast QLD Australia
    Husqvarna Motorcycle:
    2011 TE449
    Other Motorcycles:
    2009 CRF450R 2000 YZ125
    They are both adjustable and do not interchange. The outer plugs are the same but the pins are in different locations inside.

    The TPS should be fine, hopefully the ecu is as well. Even if it was the top sensor, it will still need resetting. You could do this yourself with a testplug set or at a dealer using the HST program.
    The base voltage for the secondary TPS is 1.1v with the electronic butterfly pushed closed.