Cylinder-head Temperature Sensor

[armydoc78]

I just upgraded my 883 Sporty to a 1290 cc. Apparently when doing the work, I somehow broke the Cylinder-head Temperature Sensor. The H-D dealership explained to me that its like the choke for an EFI. The part is on order and should be here next week, but can I ride it until then without damaging the motor? I need to break-in this new motor, and the longer I wait the longer I have to ride "easy." Thanks!

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[mowdoc]

I know very little about the Harley EFI but I do know a few basics about EFI in general.

First off - any gasoline engine runs with an air/fuel mixture. When this mixture gets lean, not enough fuel for the amount of air flowing, the engine runs much hotter and can cause a lot of damage. If it gets rich, too much fuel for the air flow, performance goes down and problems like hard hot starting and fouled spark plugs happen.

Also, any gasoline engine requires the mixture to be temporarly richer for cold starting (choke) and increasing RPM. When you twist the throttle to go faster the EFI knows this thru sensors at the throttle body and crank/cam positon so the controller (computer) increases the amount of fuel injected into the intake charge. Once the engine has warmed up to running temp or you have reached the speed you want and roll back out of the throttle the controller senses this and returns the mixture back to the optimum ratio.

The head temp sensor is the devise that tells the controller what the engine temp is (or at least what range it is in such as cold, running temp or hot). Based on this input from the temp sensor the controller follows a mapped plan (program) to manage the air/fuel mixture. Oxygen sensors down stream from the cylinder in the exhaust pipe monitor how things are doing by sampleing the exhaust gas and make fine adjustments with-in a range to get the best performance from the engine.

Now - when the temp sensor is not working and gives no report to the controller, most EFI engines resort back to a map (program in the controller) called "limp home" mode which will run the engine somewhat less efficent than normal but will get you home. It will also set a code so a tech can diagnose why the engine is running poorly.

To answer your question about riding your new engine on a limp mode I would say you could, and without damage, but you won't like it at all. If I were you I would just wait untill next week and get your bike right before firing up the new mill. Maybe spend extra time with the wife/girlfriend or BOTH to help pass the time until the new sensor arrives.

I'm sure some of the Fuel Injection guys will chime in and offer a lot more than I just did but that is my "nutshell" version of EFI. There are many more things to know about it and you can write books if you go all the way into the subject with details

Please pardon my spelling, I was hurrying

mowdoc

[bmxatv]

i'm by no means an efi major but i do know this......my temp sensor was pinched during the breakdown of my motor and oil leaked all over the fuking place. my guess is, your motor won't run right without it but that doesn't mean you can't. i agree with mowdoc, bang the wife/girlfriend, maybe kick the dog and wait for the temp sensor.

[HOTLAP]

I'd wait, especially with the motor not broken in yet.