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Hi guys I am new to the 4 stroke world and I was wondering if it is normal for the header to get substantially hot even though the bike had only been idling and slightly revving for like 20 seconds

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It's a combination of a high idle speed, a slightly retarded ignition timing and a aggressive camshaft. All perfectly normal for a race inspired motor.

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It's a combination of a high idle speed, a slightly retarded ignition timing and a aggressive camshaft. All perfectly normal for a race inspired motor.

 

 

It's primarily due to a very thin exhaust head pipe. The head pipes on your car would glow too if they were that thin. The exhaust gasses exiting an engine with a correct air/fuel ratio will be in the 1200F range. Guaranteed to make a thin stainless or titanium head pipe glow.

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Nice video!!! Buts that's a race motor. I don't think I've seen a tamed down motor (enduro or xr50 or ttr dzr) glow the header like a mx bike.

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Hi guys I am new to the 4 stroke world and I was wondering if it is normal for the header to get substantially hot even though the bike had only been idling and slightly revving for like 20 seconds

 

A lot of guys will tell you it's normal to see a cherry red header, and I have seen enough of them to know it happens a lot.  I also know that properly sealing the head pipe to the head with a new crush washer will keep it from glowing red and popping on decel and running less than optimally most of the time.

 

The reason the pipe gets superheated is because gasoline ignites in the presence of air when it is hot enough.  It doesn't ignite at all with no air.  No air, no ignition, so sealing the header stops the cherry pipe, in my experience 100 percent of the time, including just this past weekend.  I put a new pipe and crush washer on, installed in order, fired the bike up and got the red head pipe.  So, I backed off on the mid-pipe clamp, torqued the head pipe holder nuts down about 1/4 turn more, tightened the mid-pipe clamp and  . . . . surprise!  no more red head pipe.

 

Popping on decel happens for the same reason.  The throttle shuts down the air, but there is unburnt gasoline.  When the gasoline hits the hot pipe and mixes with air in the pipe, you hear pop-pop-pop!  No air, no pop, no red pipe.  FWIW.  If the bike is running fine and not annoying you with popping, the red pipe won't hurt anything.  It isn't an emergency.  Just wait for a rainy day and fix it after you check your valve clearances, which you should do now if you haven't yet done so.   ;)

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Watch the exhaust on this engine. :thumbsup:

 

Nothing quite like a 17,000 rpm break-in... :lol:

 

What the hell WAS that? You don't break in an engine by free revving it.

 

More likely, it was going to be scrapped so they put on a show with it. Turned the fuel off near the end for extra theatrics.

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What the hell WAS that? You don't break in an engine by free revving it.

More likely, it was going to be scrapped so they put on a show with it. Turned the fuel off near the end for extra theatrics.

thats what i was thinking

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What the hell WAS that? You don't break in an engine by free revving it.

 

More likely, it was going to be scrapped so they put on a show with it. Turned the fuel off near the end for extra theatrics.

 

 

Whatever it was, it was bad ass. Just listen to how quickly that engine builds revs.   :thumbsup:

Edited by Chokey

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