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jtanman

Why do some riders hold their hand behind the exhaust of their running bike?

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I most frequently see it after someone starts their bike cold. Holding one hand behind the exhaust and sometimes pulsing the throttle with the other. What's the deal? Checking the temp? Exhaust pressure? I see it so often that I sometimes find myself doing the same thing and then think "why did I just do that? I have no idea what that's even for" 😆.

I once rode single track behind a guy who was constantly reaching his hand back behind his exhaust mid-ride while coasting along. Seemed a little silly.

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Its a KTM thing.  They do it to make sure the bike isn't spitting little bits of the engine out of the exhaust.

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Posted (edited)
32 minutes ago, jtanman said:

I most frequently see it after someone starts their bike cold. Holding one hand behind the exhaust and sometimes pulsing the throttle with the other. What's the deal? Checking the temp? Exhaust pressure? I see it so often that I sometimes find myself doing the same thing and then think "why did I just do that? I have no idea what that's even for" 😆.

I once rode single track behind a guy who was constantly reaching his hand back behind his exhaust mid-ride while coasting along. Seemed a little silly.

image.png.271301445782a7e73a38337b1794e92d.png

I don’t truly know why - perhaps it’s a way to get a basic feel for how your jetting is doing on a carburated bike? (Referring to the mid ride guy)

Edited by RoboD
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It’s a Honda XR thing. They’re trying to find reasons why they can’t keep up with their friends who are riding KTMs. 

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28 minutes ago, 69fastback said:

It’s a Honda XR thing. They’re trying to find reasons why they can’t keep up with their friends who are riding KTMs. 

No problem, everyone I ride with is on a Honda or Yamaha. :D

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Just like many things regarding motorcycles, it's based on a "learned feel."

Wrenches (that are good,) can tell how an engine's overall health is, by the exhaust pulses.  (Barring a catastrophe.)  

Cam wear-timing/Compression/valves/intake "jetting"/ECM fueling-timing adjustments. Even fuel quality can be detected, by the "learned" hand. 

Exhaust odor is another tool to use.  

Doing it when you know the engine is healthy, and later, you notice a "change," this gives you heads up. Especially if you NEVER ride the bike. (Like a factory wrench.) Only the rider, rides the bikes, never the wrenches. 

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I do it on bikes that crank but won't start to see if it's getting fuel or not. Can smell it on your hand.

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You can tell if it’s burning oil it is rich. On liquid cooled engines, if it’s blowing coolant. I sure don’t do it every time, or even ever, when it’s running right, but for diagnosing a problem, yep.

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Telling you guys it's just what we do lol like to feel of it blowing hand back idk . I use to race in winter and would warm hands up that way waiting on line

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I've been riding dirt and street bikes over 40 years..... and I have no idea why. Other than it becomes a habit 

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My son does it all the time when warming up his bike and when he’s on the starting line. He’s admitted there’s no reason for it, he just likes the way it feels and gets him ready to ride or race. 

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They are catching the excess power from the engine.  It reduces arm pump.  

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1 hour ago, indy rider said:

Quite often I see pro riders do it on while sitting on the start gate. Are they diagnosing an engine problem too? :excuseme:

The "starting gate" isn't the place to diagnose. It might be the place to "re-affirm" tho...

(Yes, I know you were kidding, as nobody could be this stupid.)

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I've seen our YFZ 450 blow empty beer cans off my desk in garage upon startup, but no, I've never really put my hand over exhaust 🙂

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It is a habit for every bike rider .   Feel the heartbeat ,  catch the warmth , smell the flowers ,  No other reason than  ,   It's  what you do  .....  calming effect ....  

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Because they’re trying to cover up the smell of cigarettes on their hands so the wife doesn’t chew them out after the ride. 

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