Throttle kills my engine - Please help

AidanB

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Hi guys. I've lurked on the forum before but just made an account to post this. Hopefully someone else has had a similar experience, but I haven't been able to find any threads that helped.

The problem I have is that too much throttle cuts off my engine. This is shown in the video below, but basically I can only get to around 4-5k RPM in neutral before the engine just dies. Blipping the throttle too hard also kills the engine. The bike idles perfectly. Here's the story:

I rode my bike in yesterday morning and it ran great, as it has for the ~2k miles I've owned it.
After riding yesterday I replaced the rear tire as per these instructions:

I did my test ride the day after (today). I stalled on the way out of the garage, which was weird, but I didn't think much of it at the time.
I made it 1/4 mile down the road to a gas station. After filling the tank (I always use premium), I was barely able to get the engine to start. I think this is because I was trying to give it throttle while starting.
After that I could barely rev the bike enough to move. I limped it home at roughly 10 mph.

I tried idling the bike for exactly 15:30 while sitting on it, as some posts have suggested that this "resets" the ecu. That had no effect. It seems to me like an electronic issue, but the only electronic component I touched was the rear ABS sensor when I removed it for the tire change.

 

Formula390

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I watched the video, and your motor is still cold. You need to watch your throttle inputs when the engine isn't yet up to temp. These bikes run lean down low and with a cold engine and a surge of fuel like that, yeah... you can stall the motor. Once it's up to temp, that should stop happening. They all do it. If it's only doing it in neutral and while the engine is cold, who cares.

The only other thing I can think of is what does your air filter look like? Engines are air pumps. If the air filter is dirty, you could be flooding the motor with fuel because the AFR ratio is totally wacky by not getting enough air. Who knows, you might have used a rag on your hands while wrenching on the bike, and sucked the rag into the intake. I had a customer bring me a bike once with similar issues, and there was a big shop rag which had gotten itself sucked into the intake and was choking the engine for air.
 

AidanB

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Thanks for the response. The behavior is the same when warm and in all gears. I can check the air filter when I get home. I'm sure dirt is not the problem since it ran perfectly before servicing, but perhaps I did introduce something into the intake.
 

Formula390

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Thanks for the response. The behavior is the same when warm and in all gears. I can check the air filter when I get home. I'm sure dirt is not the problem since it ran perfectly before servicing, but perhaps I did introduce something into the intake.
So.... what's the word? Did you suck a rag into your intake? Mouse make a nest with your air filter?
 

AidanB

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So.... what's the word? Did you suck a rag into your intake? Mouse make a nest with your air filter?
Pretty much...
I didn't actually know where the air box on my bike was. In the process of replacing the fuel filter I found it and realized that the intake was blocked by my new stuff-sack backpack.

That was a lot of work for nothing - but at least I learned a lot about how the bike works from taking it apart.
 

Formula390

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Pretty much...
I didn't actually know where the air box on my bike was. In the process of replacing the fuel filter I found it and realized that the intake was blocked by my new stuff-sack backpack.

That was a lot of work for nothing - but at least I learned a lot about how the bike works from taking it apart.
Yeah, sounded like a dirt packed filter or a rag or other obstruction. On the plus side, that experience is significantly worth far more than its weight in education. Engines are at their core, air pumps. If it's acting wonky like yours was, and it started suddenly after working on it, it's ALMOST always going to be a sucked in rag, or similar blockage.

Glad you got it sorted out.
 
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