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[solved] random hesitant acceleration on low rpms...

GhostInTheHyo · 5 · 466

Offline GhostInTheHyo

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Hello!
I'm here to ask for your ideas and help to find what is going on.

Long ago had bad acceleration from stops and slow speed and adjusted the TPS,  this fixed mostly the problem it runs SO MUCH predictable on low rpms, but still there is some inconsistency on acceleration, I'm trying to find out what it is... I have tried many things that I'm going to list below, if you could help me get ideas what it could be, would be awesome. The problem seems to be temperature related.

 :'( The symptoms are:
-This happens mostly when hot engine and hot weather (also when engine is warming up from start up, but this is expected?): accelerating from a stop, giving little throttle the bike hesitates and have low power (exhaust sound different like bad mix) but if I keep giving more throttle or give it violently it eventually picks ups and have all of a sudden all the power.
-After this hesitations happens sometimes it happens again in succession or sometimes is just once and the bikes rides smooth after it varies a lot.
-This problems happens from stops and low rpms accelerations (up to about ~4krpm).
-It feels like the bike don't wants to accelerate and I have to push the throttle to pass this "lazy start zone" sometimes.
-It gives insecurity of not knowing if I will be able to start fast in a corner or stop light.

 :oOther info:
-The bike never stalls.
-High rpms is good, full speed no problem.
-Stable idle.
-Bikes sometimes hesitates to start up, like a hiccup. Rarely it fails to start, but at the next try it starts no problems when this happens.
-Oil is good, regularly changed, sintetic, filter too.
-Air Filter is new (problem was the same with old one).
-battery Yuasa, changed 2 years ago.
-Voltage measurements off: 12,6v on idle:13.5v - 14v, and at 5000rpm:14.5v - 15v (I looked at my on board voltmeter while experiencing the issue and showed normal voltage readings)
-Spark plugs have some use now, but with old ones the problem was the same.
-New spark plug cables, NGK racing. (with old OEM ones the problem was the same)
-Temperature is good: 3 Bars on normal riding, 4 on heavy traffic.
-I cleaned the IAT sensor in the airbox, trying to fix, but no change.
-I cleaned the IDLE Valve. It had some oil and muck, but no change.
-Checked for vacuum leaks with engine running, splashing wd40 and contact cleaner on outside of air intake lines and idle lines, no change on idle.
-Checked with another ECU. same thing.
-Clutch safety switch bypassed.
-No FI indicators.
-Both coils have been replaces for new ones, behaves the same.

 :P On last weekned I went on 9am trip to mountain road (top at 3000m altitude from my home at 550m altitude)  rainy day and somewhat cold. Bike worked PERFECT all the way up no hesitation never. When going back home at 1pm no more rain and somewhat hot, I experienced again hesitation near home and some exhaust bad mix sound spurts, like sometimes happens.

soo.... any ideas? maybe the IAP sensors are dirty with oil? or maybe the TPS is bad?, but if TPS is bad it does not explain the perfect throttle on my trip to the mountain, also i can rule out clogged fuel filter due to nice ride last weekend too. The problem is definitely temperature dependent but is somewhat random.
« Last Edit: January 01, 2022, 07:40:37 PM by GhostInTheHyo »


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