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carbon rocks?

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i was working at the toyota arenacross in wilkes-barre pa. when the bikes were at the startin gate and revvin their bikes, i noticed carbon deposits about the size of a stone being shot out the back of the exhaust. i have never saw that happen before. can any1 elaborate on how they build up like that?

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that dont sound normal to me at all...

that sounds like packing blowing out.... or some really bad mantenance.

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i was working at the toyota arenacross in wilkes-barre pa. when the bikes were at the startin gate and revvin their bikes, i noticed carbon deposits about the size of a stone being shot out the back of the exhaust. i have never saw that happen before. can any1 elaborate on how they build up like that?

Normal. Why do you think the USFS requires "spark" arrestors to legally ride in national forests?

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Should be packing

Snipped from the web. There may be some packing matterial also, but built up carbon can and does get ejected out the sparky.

Exhaust Particles - All internal combustion engines produce exhaust particles which are predominately carbon with contaminates. These particles originate from deposits formed on the internal surfaces of the engine or exhaust system and, depending on their exact origin, may be expelled at temperatures in excess of 3,000 degress F. Depending on the nature of the contaminates, these particles are capable of glowing or sometimes flaming combustion. When expelled through the exhaust system into the atmosphere, the combustion process may continue or even be accelerated during flight. Such particles, if larger than 0.023-inch in diameter and at temperatures of 1,200 degrees F are capable of igniting cellulose materials on contact.

As anyone who has ever rebuilt a two-stroke top end can tell you, the piston and parts of the cylinder and cylinder head often have carbon and other gunk built up on them. Four-stroke engines can contain, and expel, similar deposits. Like the report says, small particles of this gunk may detach and be expelled through the exhaust system. Having been in contact with very hot parts of the engine, these particles can themselves be at a very high temperature when expelled. So a spark arrester is important insurance for any bike that will be ridden near trees or brush.

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With high octane fuel they run cooler at 'idle'. Those bikes are set up to run, more or less, at WOT the entire time they are running. Therefore, any time they are not at WOT, they are too rich and too cool and carbon builds up and is then expelled when revving at the starting line.

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With high octane fuel they run cooler at 'idle'. Those bikes are set up to run, more or less, at WOT the entire time they are running. Therefore, any time they are not at WOT, they are too rich and too cool and carbon builds up and is then expelled when revving at the starting line.

yea thats what i was thinking was happening, because the amatuers didnt have that happen much if at all

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i was working at the toyota arenacross in wilkes-barre pa. when the bikes were at the startin gate and revvin their bikes, i noticed carbon deposits about the size of a stone being shot out the back of the exhaust. i have never saw that happen before. can any1 elaborate on how they build up like that?

Did those bikes have to meet a certain sound level requirement?

.

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