Warm start problems
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4th Gear
Joined: Oct 2007
Posts: 8
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Warm start problems
I'd like to see if anyone has had a similar problem or knows what might cause this. I have an '07 Touring bike with 26,000 miles and it just started being hard to start when warm. It always runs fantastic, hot or cold, and starts right up when cold. Every time. The bike is pretty much stock except for Rush pipes and a upgraded breather.
Trouble is when the bike gets warmed up it just barely starts. The starter turns over just as fast as always but the engine sometimes takes 5 or 10 seconds to catch. As soon as the engine cools down to a certain point, it starts on the first pop again. It's very predictable and extremely annoying when you stop for gas. I replaced the plugs and, as I said, it runs great otherwise. Any help is appreciated.
By the way, this is a great forum. I've found a lot of issues/problems and fixes out here that the dealer swears he has never heard of.
Trouble is when the bike gets warmed up it just barely starts. The starter turns over just as fast as always but the engine sometimes takes 5 or 10 seconds to catch. As soon as the engine cools down to a certain point, it starts on the first pop again. It's very predictable and extremely annoying when you stop for gas. I replaced the plugs and, as I said, it runs great otherwise. Any help is appreciated.
By the way, this is a great forum. I've found a lot of issues/problems and fixes out here that the dealer swears he has never heard of.
Intermediate
Joined: Sep 2008
Posts: 37
Likes: 1
Hot Start Problem
I've had a problem with mine a couple times and found the exact cause on my bike. I've got an '08 FXDC.
The EFI system uses different startup fuel depending upon the cylinder head temperature. When the engine is hot, it uses much less fuel to start.
I found that after riding my bike in the rain a couple times, the cylinder head temp sensor corroded enough at the contact with the wiring harness that it was giving bad temperature readings to the computer. My recollection is that I was getting cylinder head temp readings around 90 degress when the head temp was over 200. The result was that the bike was sending far too much fuel to start. The short term solution is to crank for a second and then open the throttle to wide open - which is the flooded start procedure according to the manual.
I've had to take the connector off of the cylinder head temp gauge a couple times and abrade corrosion off of it.
The way that I found the solution is that my starting problem happened to occur while I was refining my tune with the TTS MasterTune device, so I happened to capture an event which showed the cylinder head temperature reading fluctuating instantly between upper 200 degree range and about 90 degrees.
I don't know if there is any way to display the engine temp reading being sent to the computer without something like MasterTune. So it may not be easy to diagnose on your own. But, if you just remove the connector from the cylinder head temp sensor and clean the sensor and push the connector on and off several times you'll know on your next ride if that's the problem. It solved my issue right away.
Good Luck.
The EFI system uses different startup fuel depending upon the cylinder head temperature. When the engine is hot, it uses much less fuel to start.
I found that after riding my bike in the rain a couple times, the cylinder head temp sensor corroded enough at the contact with the wiring harness that it was giving bad temperature readings to the computer. My recollection is that I was getting cylinder head temp readings around 90 degress when the head temp was over 200. The result was that the bike was sending far too much fuel to start. The short term solution is to crank for a second and then open the throttle to wide open - which is the flooded start procedure according to the manual.
I've had to take the connector off of the cylinder head temp gauge a couple times and abrade corrosion off of it.
The way that I found the solution is that my starting problem happened to occur while I was refining my tune with the TTS MasterTune device, so I happened to capture an event which showed the cylinder head temperature reading fluctuating instantly between upper 200 degree range and about 90 degrees.
I don't know if there is any way to display the engine temp reading being sent to the computer without something like MasterTune. So it may not be easy to diagnose on your own. But, if you just remove the connector from the cylinder head temp sensor and clean the sensor and push the connector on and off several times you'll know on your next ride if that's the problem. It solved my issue right away.
Good Luck.
Intermediate
Joined: Sep 2008
Posts: 37
Likes: 1
One more thought
I forgot to ask whether this has happened since the bike was new, or if it developed over time.
If it's always been this way, then it's possible that the factor map is just not right for your bike. There is a table that sets the amount of starting fuel based on cylinder head temp.
If the problem has developed over time, it's possible that it is just the corrosion issue.
Air, fuel, spark - right combination and right time will always work. If the plugs are sparking then it is an air/fuel mixture issue.
If it's always been this way, then it's possible that the factor map is just not right for your bike. There is a table that sets the amount of starting fuel based on cylinder head temp.
If the problem has developed over time, it's possible that it is just the corrosion issue.
Air, fuel, spark - right combination and right time will always work. If the plugs are sparking then it is an air/fuel mixture issue.
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