Hi guys need a little help there is a nasty crunching sound from under my engine near the front sprocket if i roll the bike back and foward wile not sitting on it theres no sound but as soon as i sit on it and go in to 1st 2nd and so on theres a horrible grinding or cruncing noise its due for new chain and sprocket set i took the bike to a garage he said the engine sounded fine this was a day before it started making the noise got me really worried any help would be great.