My EVO is making the sort of 'rocks in a can' noise, but really..it sounds more like tiny pebbles. It's been doing it for a little while, I just haven't been really worried about it because the bike seems to be running great. What is the cause of the sound, and do you think I should be looking to rebuild it within the next 10,000 miles or so?

 

That's called pre-detonation(knocking,pinging). Crappy gas and lugging in high gear can cause that. Prolonged periods of it can cause big problems.

 

Wow, I wasn't expecting that...I know what detonation sounds like in cars, trucks, etc. I never would've dreamed that would have been detonation. Hmm..i'm still kinda skeptical..

 

My Evo starting making noise, turned out to be the crank bearing going out. Major scoring where the breather gear lives. Had to do a complete tear down and have the case machined and sleeved. Running good now. Hope yours is something else.

 

Wow..hope mine is something else too. [8D]

 

Easy way to find out Michael. Run it almost out of gas and fillup with 91+ octane. See if that stops or slows the knocking you are hearing.

Bob

 

Will do that Cadillac..I actually need to fill up this evening, and i'll fill it up with 93 and see what kind of noises she makes. It calls for 87 on the sticker on the downtube, but the bike has the Longshots on it, as you can see in the picture in my sig, and I suspect that the carb wasn't rejetted when they changed the pipes.

 

Try to understand that these days gas in most places is 10% ETHANOL. That makes for a cleaner burning fuel (so they say) but it leaves a whole lot to be desired when optimum performance and peak octane is concerned.
Does it happen in gear while going along ? Or does it occur when you're taking off in each gear ? Possibly lagging ?
Evo's can take a whole lot of punishment. Just make sure it's not self induced....

 

Nope, just happens when I get on it hard, or under any other such load. For an idea of what it sounds like, I thought it was the 'shells' of my gas caps vibrating against the inner part at first, but then the other day I opened the throttle up (my throttle doesn't roll back itself) then took both hands and held the gas caps, and still heard the noise...so ruled that out.

 

If your throttle doesn't roll back on its own, that means your throttle and idle cables are out of proper adjustment. I would highly recommend you get a manual and properly adjust them. Your throttle should roll back easily and smoothly as soon as you release it. Also, check and make sure your "friction brake" isn't being applied to the throttle. On your right controls, between the cables there should be a little ****. Turn it to the left as you are looking up at it (counter-clockwise) to ensure that it is not making contact with the throttle sleeve.

That could be very dangerous in a panic stop situation. You should not leave your throttle in this shape. Just my 2 cents...