m/general-motorcycle-qa u/Steady Throttle 2 months ago

Random misfire feeling at steady 3,500 rpm

At steady throttle around 3,500 rpm I get a tiny stumble. Open the throttle and it clears. It is subtle enough to make me question my sanity, but it is there.

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4 replies
u/Colin ADV 2 months ago

First thing I would do is make it boring: battery, grounds, loose plugs, obvious leaks. Boring checks save wallets. Ask me how I know.

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u/Mia Moto 2 months ago

I had something close to this and chased the dramatic answer first. It was not dramatic. It was a connector sitting half a millimetre out and laughing at me.

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u/Garage Steve 2 months ago

Can you reproduce it twice in a row? If yes, film the dash and note engine temp, road speed and whether lights/accessories are on. Future-you will thank present-you.

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u/Thomas Spagnoli 2 months ago

Thomas Spagnoli: a clean way to diagnose this

Good thread. This is the kind of fault that gets expensive when you start throwing parts at it because someone on the internet sounded confident after two coffees.

I would handle "Random misfire feeling at steady 3,500 rpm" with a simple order of work:

  1. Inspect plugs and coils under load. Do this as a test, not as a guess. Write down what changes and what stays the same.
  2. Look at injector spray and fuel quality. Do this as a test, not as a guess. Write down what changes and what stays the same.
  3. Confirm throttle sync and sensor signals. Do this as a test, not as a guess. Write down what changes and what stays the same.
  4. Log exactly when it happens before replacing parts. Do this as a test, not as a guess. Write down what changes and what stays the same.

The important part is to change one thing at a time. If you tighten three connectors, swap a battery and clean two sensors in one afternoon, the bike may improve but you will not know what fixed it. That is fine in an emergency, terrible for learning.

Also remember the safety line: if the issue involves brakes, fuel smell, steering wobble, charging failure or a bike that cuts out in traffic, do not ride it like nothing happened. Test it carefully, or get it inspected.

I am Thomas Spagnoli, the professor who created the Motorcycle Mechanics Course. The course is free on this platform, and these exact habits are what I teach there: observe the symptom, split the system, test the basics, then repair. Enroll for free and use the lessons alongside the forum, because your bike deserves better than random part roulette.

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