Weird sound when engine is hot

[brimic]

I noticed that somewhere in the top of the engine there is odd sound when the engine is hot. I notice it when I ride to work and back after about 20 miles or so. Sounds sort of like a handful of gravel swishing around in a coffee can.

Where do I start looking for the cause? Could it be a worn lifter or rocker?

[misterT]

That sounds like it could be detonation, which would be very bad. What do your plugs look like, are they white or grey? Have you made any performance upgrades?

[brimic]

Ah, I kind of had that thought in the back of my head but wasn't sure, I've been filling up with 93 octane on the last 2 fill-ups to see if that made the difference- it hasn't.

I didn't pull the plugs yet but will tonight.

Only upgrades I made was a free flowing air cleaner and exhaust along with carb mixture adjustment. I replaced all of the top-end gaskets this spring due to a blown head gasket, and rechecked the carb adjustment afterwards.

[brimic]

I just looked at the plugs, they both look the same.

I "think" they look normal- a light gray ground electrode, the insulator and center electrode look almost new, and the rest of it has a bit of carbon fouling.

[brimic]

I also hear this sound constantly, during acelleration/decelleration, and idling.

When I first heard it I thought it was my rear gas tank bolt coming loose again, but like I said, it doesn't make the noise until the engine is hot.

I'm also running Mobil1 Vtwin oil,not sure if that makes any difference or not. Bike just rolled over 15,000 miles yesterday.

[Kwest187]

Any detonation I've had is more like a piercing ping...and usually happens when throttle is added and it doesn't really matter if the motor was hot or not...your described sound seems more like a bearing issue...and since it comes on when warm and the oil thins that would make sense...I don't want to freak you out though...your bike is a 1990 correct?
it could be many things and even though it sounds top end it could be from anywhere...the primary chain is where I'd look 1st...it could be loose or the shoe could be wearing out and the hot oil in there breaks down and your hearing the chain rub on the shoe bracket...
also if the sound "just started" and you didn't change timing or jetting or pipes...there is no reason for it to start detonating...but stranger things have happened-
So yeah-check the P-Chain and the if no clues there put a mechanics stetho or a screw driver on it while the sound is happening to try to zero in on it better-
Good luck

[Kwest187]

Is that a synth oil?
What were you running before...synth oils are lighter and bring a bunch of new sounds when you 1st switch that were muffled in the thicker oil before-

[brimic]

I was running the H-D dino oil in it until this spring.

I'll take a listen to the primary chain tomorrow after work.

I'm familiar with what a bad bearing or pinging sounds like from car engines, not sure if that applies to bikes.

[xHDrider]

take a broom handle and put it to your ear. move it around to different locations. if you have a problem area you will hear it. I have a stethoscope for engines but its too loud, for me the stick works the best.

[brimic]

I tried the screwdriver check last night though it probably didn't tell me much becasue I didn't have the engine hot, but the rear head, especially near the exhaust side was making the the gravelly grinding sound. I can't check it today, didn't ride it to work because we are expecting thunderstorms all day today.