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What is the hot start/compression release

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A hot start and compression release are two different things.


A hot start allows more air into the carb, thus leaning out the mixture.   When a motor gets very hot, it's often hard to start because the mixture is too rich.


A compression release opens the exhaust valve a bit to allow the motor to turn over easier when starting.  It should disengage when the motor is running.


What you have on the 250x on the handle bar is a hot start.   The decompression setup is internal and automatic.  


 With the hot start, if your bike was jetted correctly, then on a fully warmed up motor what should happen is:


1. When pulled slightly, the revs should increase

2. When pulled all the way, the motor should die.


 If it didn't die, then you are too rich on your slow circuit (assuming you were at idle).


You should also be able to pull the choke out and the motor should die.   If that didn't happen (the motor die), then it would indicate a lean condition with the jetting.


You did no harm in pulling it with the motor running.



Edited by Jim Dettman
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Jim is 100% correct. I was going to answer your question, but Jim did an excellent job.

Study the owner's manual for your bike. It's very good. If you have any further questions about your bike, there are many on this forum who have torn these bikes down, rebuilt them from the ground up, and know every detail of pretty much every part. We're happy to share :-)

Further to what Jim posted, the engine on your X has an automatic decompression function built in that activates when the engine RPM is less than idle (about 1700 RPM). It causes the exhaust valves to open very briefly during the compression stroke to make it easier to kick over the motor (or easier on the electric start). This is implemented using a smart, simple little mechanism that uses the centrifuge principle with a weight and a spring located on the right side of the cam shaft.

The hot start lever moves a small cylindrical brass slide valve on the front side of the carburetor that allows more air into the carb, which as Jim explained, causes the mixture to lean out so you can start the engine when it's hot.

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