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Engine running bit weird, how to proceed? |
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Fazer Fail 
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Joined: 03 Sep 2025 Location: Greater Glasgow Status: Offline Points: 25 |
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 Posted: 24 Sep 2025 at 10:56 |
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opened up my ECU the EPROM has yellow sticker PA07 anyone know what that is?
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Spoonz
Admins Group
Joined: 11 Feb 2008 Location: North Devon Status: Offline Points: 10957 |
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Posted: 24 Sep 2025 at 12:14 |
Thats the oem eeprom for a falco. Euro versions should have the trimmers enabled.
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Fazer Fail
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Joined: 03 Sep 2025 Location: Greater Glasgow Status: Offline Points: 25 |
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Posted: 24 Sep 2025 at 12:58 |
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thanks once i get an afr meter will have a play
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ChrisIBK
Moto3 racer 
Joined: 15 Aug 2025 Location: Innsbruck Status: Offline Points: 31 |
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Posted: 09 Oct 2025 at 21:34 |
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Think I have figured a big part of my "weird engine running" situation, after some headscratching - the check valve on the clutch activation line was actually non-functional, and pretty messed up by brownish goo on both ends - I suppose it could actually spring back into life if heated up, liquifying that goom which might explain a bit of the "tuning success" I had on that warm day with the bike reaching at the end above 90° water temp... Can someone confirm - from what I understand, even with a check valve installed, this clutch actuation circuit will allow some air to bypass the rear cylinder throttlebody at idle/very slight throttle - as the checkvalve will allow the flow into the intake port with a significant pressure differential, and the pressure it sees at the other end is the above-the-throttle hose - which will indeed be under higher pressure (a very slight vacuum) than the intake (a rather strong vacuum) when the throttle is closed. So I guess that's why we're told to open the rear cylinder bypass screws a lot less than the front, right?
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Spoonz
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Joined: 11 Feb 2008 Location: North Devon Status: Offline Points: 10957 |
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Posted: 09 Oct 2025 at 22:13 |
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I don’t think the bypass screws position was by design intended to influence the ppc. The rear bypass is generally set much less than your setting from the factory with stock eeprom. Whether adding bypass has any influence in practice I don’t know. You should feel the clutch lighten at idle if it has. Is your check valve red as they got replaced by an updated part.
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ChrisIBK
Moto3 racer
Joined: 15 Aug 2025 Location: Innsbruck Status: Offline Points: 31 |
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Posted: 10 Oct 2025 at 10:56 |
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yes it's a red plastic valve, seemed rather cheap to be honest (not just owing to the fact it failed on me). Have ordered some generic ones from amazon as I don't quite see the point for ordering that thing from the Aprilia dealer for €40, but maybe the new part is better?
Well with the check valve in place, with the vacuum lines as installed on my bike, it seems to me inevitable that the rear cylinder will suck a significant (6mm tube's worth) amount of air through the clutch actuation circuit at idle and near-closed throttle. Perhaps the diagram there shows a different setup to my bike, but what I'm seeing is closer to this general schematics: -vacuum port above TB ----------------------\ | 3way-junction>----------Clutch | -vacuum below TB--- check valve (<-dir)---/ So to say, with the check valve actuated at closed throttle (as the pressure at above TB and clutch is clearly much closer to atmospheric than right at the intake port where the engine is trying to suck in air), what is to prevent a 6mm-hose-worth of vacuum to continually pass from the "above TB" port to the "below TB" port, bypassing the TB? Or to put it different, am I missing information/insight, or some parts on my bike? |
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Spoonz
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Joined: 11 Feb 2008 Location: North Devon Status: Offline Points: 10957 |
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Posted: 10 Oct 2025 at 12:51 |
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Im not 100% sure which above tb port your referring to. If you mean the port that vents the ppc to the airbox, then that is closed off as the throttle closes by the spindle the butterfly rotates on. If the check valve is functioning as it should then the port closing and the check valve operating should more or less coincide.
I know Gabro who tunes Aprilia’s played with ppc on his race bike and the only way he could get any real world difference to the ppc was to pull vac from both cylinders to the ppc. The new ppc valve from Aprilia was a totally different design but the same in function, just more robust materials.
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ChrisIBK
Moto3 racer
Joined: 15 Aug 2025 Location: Innsbruck Status: Offline Points: 31 |
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Posted: 10 Oct 2025 at 13:05 |
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Ah ok, I guess there was indeed an insight missing - the misunderstanding is in how that "above the throttlebody" port is connected - to me it looked like it just taps into the air column. If you tell me it's indeed blocked off any time the the throttle is closed and that part of the diagram were the air flows through the throttle axis is not just coincidental, that should take care of if all. I'll also try installing dual-check valves (arriving today) as right now that clutch actuation turns out a bit of a curse, quite clunky indeed, lots of force required, and often impossible to get her into neutral with the engine running at a red light. Looking forward to the bike running, shifting and idling as it should, hopefully I can make good use of that rare october sun we have right now...
Thanks a lot for all your help!! |
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Spoonz
Admins Group
Joined: 11 Feb 2008 Location: North Devon Status: Offline Points: 10957 |
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Posted: 10 Oct 2025 at 14:11 |
Being an early bike it probably has the big clutch oil jet. 0.9mm from memory. That fed too much oil into the clutch basket at idle causing excessive drag, hence the hard to find neutral. There were 2 revisions to the jet with the latest being 0.6. It’s not a 100% fix but it males it noticeably better. The oem slave doesn’t help but unless you invest in a third party larger piston version, it will always be heavy ish.
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ChrisIBK
Moto3 racer
Joined: 15 Aug 2025 Location: Innsbruck Status: Offline Points: 31 |
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Posted: 11 Oct 2025 at 09:30 |
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Haha I think the clutch is back on track - did the dual check valve
modification as I ordered a 2x pack anyways, and (as far as I can tell
with my previous problems) it actually feels quite good and smooth when
shifting, clutch force is definitely improved and I can easily get into
neutral at traffic lights...
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Fazer Fail wrote: