I have an air cooled single cylinder motorcycle with a bogging down(feels like something is pulling back on the bike making it struggle) problem on acceleration. After many many months of having it I can now pin point the circumstances in which it happens.
- It is throttle position specific (roughly 1/4, after this it runs fine).
- It only happens when the engine is up to operating temp (on a cold engine it is fine(first 5mins of riding are problem free))
- Trying to reset the ecm doesn't work (hold throttle 100% open then let go( almost as if the ecm isn't reading it WOT from the tps)
- It doesn't matter what speed I'm going or what the rpm's are at 1/4 throttle it happens
The only sensors on the bike are:
- Throttle position sensor (tested with multimeter and there is no spikes or jumps in voltage when slowly turning throtle, nice and smooth as it should be)
- Intake air temperature (seems to be fine) Engine oil temperature (seems to be fine)
- O2 sensor (not tested)
- Idle air control Valve( ok not a sensor but still pluged in haha)
I have ran redex through multiple times to clean the injectors, tried different petrol and I'm ruling out fuel pressure due to the fact that surely after 1/4 throttle the demands should be higher and effects of bogging be even worse.
I have also tried air intake cleaner(the spray kind) to de-coke the throttkle blade.
The valves are in spec.
Changing the air filter and spark plug makes no difference.
All this happens underload but I tested in neutral (held the throttle at demon position if you will) and I swore I heard a few pops(backfires) although I can't be 100%(I'd say im 80% certain) certain due to the exhaust noise.
Finally the are no DTC's CEL's being thrown.
What else can I check? Im all out of ideas now.
Cheers and thank you if you made it this far
The day after this post I decided to go for a ride with the tps unplugged and as expected there was a delay between throttle twist and acceleration, but the 1/4 throttle bog wasn't there.