Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Yamaha FZ1 fuel injection snatch: how to fix it

Discussion in 'Modifications and Projects' started by Loz, Feb 28, 2008.

  1. I've been speaking to a few FZ1 owners lately about the famous throttle snatch the bike suffers from. I remembered where I found info about a simple fix, so I thought I'd post it:




    Without the injection issues, the FZ1 has some serious horn factor. It's definately back on the list.

  2. It's worth saying here that the 07 and 08 have a revised computer which is much smoother, and it is relatively easy to get them to put 150hp at the back wheel. Anyone interested in getting or who has an FZ1 can find good info at http://www.yamahafz1oa.com/
  3. Thanks for the info Loz.
    The FZ1 2006 onwards realy does have awesome power for a naked.
    I guess it is as close as you can get to a naked R1.
  4. yeah I got the 07 Fz1n, havnt had any probs with the fuel injection,

    it runs like a rocket.. :shock:
  5. The way to fix it on many EFI bikes, without spending any money at all, is to simply unplug the O2/Lambda sensor in the exhaust collector. It's this sensor that's responsible for cutting the fuel on a closed throttle in the first place for purposes of lower emissions. Unplug it, and the EFI module falls back to its default mode which is to supply sufficient fuel to the engine on a closed throttle as if it were trying to maintain an idle tickover.

    Of course, if the FZ1 doesn't have a lambda sensor, then ignore my above suggestion as Yamaha must be doing something else (but most modern EFI bikes have lambda sensors for emissions purposes).
  6. mmmmm, riding snatch =P~
  7. BIKE magazine slagged the FI on the Yam, but also published a fix that involved a box of gizmos they got from the US too......
  8. That would be the second link in the OP... Ya GOOSE!

    Then there's Chairman's response, which I hope he won't mind me repeating... Something like "I'm interested in this fuel injected snatch you were talking about. Is it true they run on Bacardi Breezers?"


  9. I think you might be a wee bit confused there stewy -the lambda sensor has nothing to do with idle fuel mixtures. Its job is to trim the fuel mixtures at a constant load situation at a set throttle position ie cruising along at say the speed limit. Unplugging this will sometimes cure surging issues under these conditions.
    I think you may be thinking of the TPS or throttle position sensor. One of its jobs is to cut the fuel as you described dependant on gear position, engine speed, manifold vacuum etc etc. The snatching is a result of fuel being introduced upon opening the throttle after the ecu has cut the fuel due to the throttle being closed. Adjusting the TPS may have an effect here.
  10. Surely Andy the TPS only feeds information to the ECU and the ECU makes that decision. Pete toe Pom had the same theory, and adjusted the TPS on the Hornet9 I used to ride so it was always registering above zero. It helped, but didn't solve the issue (and I highsided the thing into oblivion soon afterwards so we couldn't test any more ideas).
  11. You're exactly right there Loz. It's the ecu that makes the decisions. But by adjusting the TPS it fools the ecu into thinking the engine is doing something different than where the throttle position actually is. I have done a bit of research as my KTM actually runs a TPS on its carby, but as you said there is no real evidence to support things either way. Not that can be noticed on a dyno anyway. Individual riders report varying degrees of improvement -or no change at all.

    PS if you take note of my first post, you will notice that I said "may" make a difference :grin: :grin:
  12. Theory aside, and you can feel free to object.

    For me, the proof is in the results. On the 675, with the lambda sensor installed, I'd get the occasional surge when cracking the throttle again after coasting into a corner with a closed throttle.

    Remove Lambda sensor. Problem is now completely gone.

    Now, I may be confused as to what the lambda sensor does, by my understanding is that it's used to measure the air-fuel ratio based upon its reading of the exhaust gases, and provide a feedback trim to the ECU. In a closed throttle mid-rpm condition, there's a lag between when the throttle is cracked and the sensor picks up the gas signal because the pipes are filled with lean-burn gases in this scenario. This results in a feedback surge as the lambda sensor is telling the ECU that the mixture is still too lean, so the ECU feeds in more fuel - which more or less acts like opening the throttle further, and the bike surges forwards until the lambda sensor "catches up".

    That's my understanding of the issue.

    When the Lambda sensor unplugged, the ECU doesn't get the feedback surge that forces it to feed in more fuel than the current TPS position and rpm is instructing it to do.

    Meh. Take it or leave. I know what worked for my scenario.
  13. The same thing as you're talking about also works on the VFR800 Stew. It didn't work on the Hornet 9 and apparently it doesn't work on the FZ1 either - that's why I thought this info might be useful to FZ1 owners.
  14. That's interesting Stew -the O2 sensor usually has a time delay programmed into the ECU before it starts to adjust the mixture. And thats after you reach a predetermined set of parameters ie high manifold vacuum constant throttle position etc etc. You can actually see it cut in on the dyno. On cars anyway.