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Rough cold idle

easterncoyote

easterncoyote

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I picked up my brand new 750 DCT last week, trading in my CBR500R. I really like the motorcycle, especially the automatic transmission. However, when I start the bike, the idle is rough and erratic until it warms up, and if I try to ride it, it will hesitate. Even when it warms up, I can still hear a slight variation in the idle, but it doesn't seem to effect the performance. I will take it back to the dealer next week, but this is quite disappointing, having a problem like this on a brand new, fairly expensive motorcycle. Does anyone have any thoughts on what might be causing this, and whether it can be easily fixed? Thank you.
 
The dealer is your best bet then. According to the service manual for rough idle next things to check are kinked gas (or vent) hoses, charging system, air intake/vacuum problems or sensors.
 
The dealership is your best bet but if you want to try a simple possible fix is to try a reset. 1. Disconnect the negative battery terminal 2. turn on the key for a minute 3. turn off the key 4. reconnect negative battery terminal 5. turn the key on and press the start button (DON'T TOUCH ANYTHING ELSE) and let it idle until it's at operating temperature (the radiator fan will kick on, usefully takes 10-15 minutes) it should work the way it's supposed to after that
 
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easterncoyote said:
Rippin, thank you, I have never heard of that. What exactly does a reset do, that it would correct an idle problem?
Click to expand...
it resets the settings for the fuel injection. There is a tolerance for variables (elevation, temp, oxygen, back pressure) and such. It's supposed to do so automatically but that's not instant, and sometimes it just acts wacky. Just so you know if you change your exhaust or do anything that would effect the engines breathing or exhaust then doing this reset would help it run better right away
 
I tried your suggestion today, Rippin, but unfortunately it didn't fix the problem; I was hoping it would. I have arranged to take it back to the dealer next week and leave it overnight so they can start it cold the next day. My fear is they won't be able to fix the problem. What happens in that case? Thank you.
 
Never stalls or nothing and it shouldn't be too rough

Just abit of rpm variation till it warns up

The CPU controlling the mixture

Just enjoy it man it's a Honda

Bulletproof
 
Good to hear I'm not the only one experiencing this, but I don't think it is normal. I haven't seen any other comments about it. I don't think a brand new motorcycle should be doing this, especially one costing over $10,000! How do you know it is the mixture, and not something else? I can hear the idle variation even after it warms up, although it is more subtle. Thank you.
 
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Well ...
I don't have proof but I leaned something as I got older ... if you listen for problems you will hear problems and see problems and become paranoid :)

I did 500 miles today on mine no issues and was very hot out

I've been hearing the chain a bit more lately ... see what I mean ? I get bored and start listening for issues and now I'm on YouTube listening to chain sounds Lol
 
There was a thread way back maybe 4 years ago where an owner fiddled with a similar problem for a long time. I believe it turned out that the bike had a bad fuel injector. I wish I could find that thread.
 
Nofear2trek said:

Yikes! This bike eats the cheaper gas, 85-87 octane.

Ray
Click to expand...

The man who owns the dealership where I bought the bike (KW Honda) recommended using the high octane fuel, though I can't remember why now. I use the Shell high octane because it is one of the only brands that doesn't contain ethanol, which is supposed to be bad for the engines.
 
rmezei said:
Let us know the outcome please I am curious
Click to expand...

It turns out you were right, though I was sure you were not :). The technician called me from the shop today to tell me my bike was ready to pick up. He said he started the bike cold and listened to it, and said all these models have that rpm variation until they warm up. He went into the technical details about the vacuum control nozzle, air temperature, etc, which were somewhat lost on me. He said even the Gold Wings are the same until they warm up. He said they have talked to Honda many times about this, as many customers have complained, but it's just the way these newer bikes are. He said they are using less expensive fuel injectors, and also trying to lean out the mixture to get better mileage. The proof for me was that they lent me a loaner bike, which happened to be the exact same bike as mine. I started it up cold today, and guess what? It behaved exactly like mine!

So I will go and pick up my bike tomorrow (it was raining today), and ride it, and be happy, and stop worrying. Thank you for your help!
 
easterncoyote said:
The man who owns the dealership where I bought the bike (KW Honda) recommended using the high octane fuel, though I can't remember why now. I use the Shell high octane because it is one of the only brands that doesn't contain ethanol, which is supposed to be bad for the engines.
Click to expand...
That man who owns the dealership should know better. IMHO

(Nc750x octane level 89, 91, 94 - north america)

Ray
 
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