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Thread: Unable to Rev - Idles Fine

  1. #1
    apriliaforum prov-nov
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    Unable to Rev - Idles Fine

    Hi I'm having an issue with my bike. It's able to turn on and idle without issue but when I give it gas the RPMs decrease and it bogs. It was intermittently dying 2x a month or so and then recently it died and I was barely able to get it home. By the time I got home I couldn't give it any throttle without it bogging. I'm not able to drive it because it just dies under throttle.

    The fast idle works perfectly, I can use it to rev to about 5k, but I can't rev at all with the throttle.

    When I turn it on I am able to rev it freely for about 20-30 seconds and then it starts acting up.

    I dropped the tank and replaced the fuel filter and all lines. I wasn't able to blow at all through my old fuel filter so I thought that was the issue, but when I put it back together on the bike the stuttering continues.

    I replaced the spark plugs (gapped at .7mm) as well as cutback the wires (only a year old) and re-seated them to the coils. I also verified there is spark.

    I had already done the brown connector mod, and I did the same to the white barrel connector with no changes.

    I checked vacuum lines on the TB and they look good.

    I set the TPS to 0, bypassed the kickstand switch by jumping the two outside connectors. Tried it without the tip over sensor plugged in. Swapped the fuel pump relay with the relay next to it.

    I hooked a fuel pump to the TB and it gets about 43 when I turn key and stays around the same when attempting to rev it.

    My grounds look good as well.

    I'm running out of ideas. It seems weird that it works for a few seconds when cold when i first turn it on but then i cant rev it without it stumbling. I was thinking possibly a fuel pump because of how clogged the fuel filter was but I get 43psi at the TB on key on, and I can use the fast idle to increase the RPMS

  2. #2
    apriliaforum prov-nov
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    Also, the battery is recent and holding power. I get a about 13.75v at the battery terminals with my multimeter while idling

  3. #3
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    Check fuel pump pressure. My would idle ok but any throttle it would spit & back fire. Wouldn't hold pressure. I always thought it would work or not but not these.
    Don-M

    2003 Aprilia Tuono
    2009 Moto Guzzi Griso 8V Sold it
    2015 EBR1190SX
    1975 Kawasaki Z1

  4. #4
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    Quote Originally Posted by Kid Thunder View Post
    Check fuel pump pressure. My would idle ok but any throttle it would spit & back fire. Wouldn't hold pressure. I always thought it would work or not but not these.
    I get 43psi at the TB when I turn key to on. It goes down slightly (to about 40psi) when I attempt to Rev it.

    When your fuel pump went out were you able to increase the idle with the fast idle lever but it died if you twisted the throttle?

    Thanks for your help

  5. #5
    apriliaforum expert jess67's Avatar
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    Check your hi pressure fuel line for kinks or damage

  6. #6
    apriliaforum expert DanV990's Avatar
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    See if you can borrow someone’s ECU and chip to rule that out. When the bike first starts from cold the ECU and chip run in a cold start mode. After the bike warms up it switches to the normal operating map. Also at normal temps there is a handoff around 4k from the idle map to the highspeed map. Maybe something has gone wrong with your EPROM for the high speed normal temp map.
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  7. #7
    apriliaforum expert DanV990's Avatar
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    Another thing I would doublecheck is that all of the clamps on the fuel hoses inside the tank are secure. Perhaps you have a loose clamp on one of the lines that you just installed. Is the new fuel filter installed the correct direction? I’m pretty sure that they are one-way. I think loose clamp or a backwards filter would show up on a fuel pressure test however.
    1985 Honda VF500F Interceptor Red
    1985 Honda VF500F Interceptor Blue
    1992 BMW K1100RS ABS
    1993 Honda CBR600 F2
    1995 Ducati 916 Monoposto
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  8. #8
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    Quote Originally Posted by DanV990 View Post
    Another thing I would doublecheck is that all of the clamps on the fuel hoses inside the tank are secure. Perhaps you have a loose clamp on one of the lines that you just installed. Is the new fuel filter installed the correct direction? I’m pretty sure that they are one-way. I think loose clamp or a backwards filter would show up on a fuel pressure test however.
    I replaced the corrugated lines from the filter, the filter in the right direction and the tiny house before the fuel pump plate. Everything was tightened down securely.

    I took some videos today and will upload them soon

  9. #9
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    Quote Originally Posted by DanV990 View Post
    See if you can borrow someone’s ECU and chip to rule that out. When the bike first starts from cold the ECU and chip run in a cold start mode. After the bike warms up it switches to the normal operating map. Also at normal temps there is a handoff around 4k from the idle map to the highspeed map. Maybe something has gone wrong with your EPROM for the high speed normal temp map.
    Do you know what temp it switches from cold mode? Once it switches I canít even rev it 4K

  10. #10
    apriliaforum expert northern phil's Avatar
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    What controls the maximum engine speed? 5000rpm max on dash till reset, could that be playing up?

  11. #11
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    Here is my bike cold, after sitting overnight:

    https://youtu.be/6dxSTve5xvo

    Here is after warming up a little bit

    https://youtu.be/MOapZdUvsig

  12. #12
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    Mine ran much worse than yours. Pump pressure seems fine if a LITTLE low when you gas it. I tried an extra pump(Ebay special, China)I had & it ran fine. Fairly easy to change pump if you had one.
    Don-M

    2003 Aprilia Tuono
    2009 Moto Guzzi Griso 8V Sold it
    2015 EBR1190SX
    1975 Kawasaki Z1

  13. #13
    apriliaforum expert DanV990's Avatar
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    Quote Originally Posted by northern phil View Post
    What controls the maximum engine speed? 5000rpm max on dash till reset, could that be playing up?
    Max RPM is controlled by the EPROM. The red light on the dash is only a shift indicator, you can set it to any RPM you like but it does not affect the rev limit.
    1985 Honda VF500F Interceptor Red
    1985 Honda VF500F Interceptor Blue
    1992 BMW K1100RS ABS
    1993 Honda CBR600 F2
    1995 Ducati 916 Monoposto
    1999 Aprilia RSV Mille



  14. #14
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    Quote Originally Posted by DanV990 View Post
    Max RPM is controlled by the EPROM. The red light on the dash is only a shift indicator, you can set it to any RPM you like but it does not affect the rev limit.
    Before i soldered the brown connector my dash reset a bunch. I can put the speed back to mph but struggle to change the shift indicator.

    i have a new walbro 255 and read that it can fit, so Iíll try and throw that on tomorrow or the next day and see if makes a difference. If so Iíll probably pick up a used fuel pump

  15. #15
    apriliaforum expert RossGuzzi's Avatar
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    I would guess a air leak. Check the rubber boots the TB`s sit in are tight.
    Tuono Racing + KTM 990 Adventure =

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