New 416cc piston, weird buzzing noise

[motrhed]

I just finished putting my 400 back together with a new JE 416cc 10.8:1 piston. The install seemed to go fine, it starts and runs just fine, no smoke or bad signs except for a new sound the engine makes now. It's a high pitched buzzing that directly follows RPM, almost like if you were zipping a zipper at 90mph, kind of a whirring, buzzing. It changes pitch but not volume with RPM. Seems slightly louder on the left side, maybe. I've rode it about 20 minutes so far thinking maybe it was the rings scraping the freshly bored/honed cylinder and would go away over time but it doesn't seem to have changed any yet.

I haven't taken anything apart yet, don't really want to but I think tonight I'll pull the valve cover off just to take a look at the top end. I did a Wiseco 11:1 piston kit about 10 years ago in my previous 400ex and I don't remember hearing this noise but it's possible I forgot about it. Has anyone heard anything like this before? Is noise like this normal while the rings wear in?

[trailrider894]

Originally posted by motrhed
I just finished putting my 400 back together with a new JE 416cc 10.8:1 piston. The install seemed to go fine, it starts and runs just fine, no smoke or bad signs except for a new sound the engine makes now. It's a high pitched buzzing that directly follows RPM, almost like if you were zipping a zipper at 90mph, kind of a whirring, buzzing. It changes pitch but not volume with RPM. Seems slightly louder on the left side, maybe. I've rode it about 20 minutes so far thinking maybe it was the rings scraping the freshly bored/honed cylinder and would go away over time but it doesn't seem to have changed any yet.

I haven't taken anything apart yet, don't really want to but I think tonight I'll pull the valve cover off just to take a look at the top end. I did a Wiseco 11:1 piston kit about 10 years ago in my previous 400ex and I don't remember hearing this noise but it's possible I forgot about it. Has anyone heard anything like this before? Is noise like this normal while the rings wear in?

Did you do a proper break in, including the heat cycles and all???

[hocman123]

sounds like maybe u didn't check ur ring gaps before in installed the piston

[motrhed]

Yes I file fit the rings myself they were all way tight out of the box filed them to JE's spec.

No I have not done the proper break in, I am in the middle of break in, or I guess right at the beginning really. It's made the noise since the very first start up, it hasn't changed. I did quite a bit of searching and reading and I've concluded the proper break-in is to not rev it too high and load it up to 1/2 throttle off and on working through the rev range, pretty much normal riding without any full throttle or high RPM, for the first tank of gas. Then change the oild and ride it like normal, and don't use synthetic oil until you've put a couple tanks of gas through it.

[Zeb400EX]

Maybe its not inside the motor. You'd know pretty quick if something is wrong inside, cause it would get louder. Mine starting making a ring rattle nose when i would rev high rpms after a put my 416 piston in and it ended up being the bottom front motor mount spacer was lose just enough to make that noise.

[motrhed]

Tore the plastics off and checked the valve clearance, might have been a little on the tight side but I wouldn't think enough to cause noise. So I took the valve cover off and looked around, everything looked great, timing chain was in the grooves, chain tensioner working properly. Pulled the spark plug too and it looked fine, didn't see any metal flakes or anything weird. Put it all back together, adjusted the valves again, and fired it up. Seems like a noise is still there but not as loud as before... maybe just the fact that the engine cooled off or maybe adjusting the valves did something? Hard to percieve a difference really but it just seems less noticeable now, almost normal.

The one other thought I had is it could be gear noise from all those gears in the crankcase. I'm running el-cheapo 10w30 oil for break-in, where I normally run Mobil 1 15w50... maybe the thinner cheaper oil is just allowing the gears to wine more?

I only had a chance to start it up and listed a few seconds. I'll have to take it out for another ride tomorrow and form a real oppinion of whether or not there is still a bad sound. For a while I was worried something was wrong with the rings, but the more I thought about it, I think it would be impossible for them to be bound up in any way, the piston-to-cylinder clearance is so small I would have never got the piston in the bore if the rings weren't sitting in the grooves where they should be. So though the process of elimination I'm a little less worried about it, but I'll follow up one I get another chance to ride. If the noise truly is decreased, I guess I'll rack it up to valves clearance being too tight?

Also Zeb thanks for the input, judging by the character of the sound I don't think it could be something vibrating but I'll take a good look at everything just to eliminate that possiblity.

[Zeb400EX]

it could be the oil. i been running 20w50 in mine. kind on the heavy side but i seeing how ex's run really hot anyway it shouldn't matter. hope it works out for ya. i am the same way any time i put mine back together. i'm alway listening for noises.

[2001400exrida]

Originally posted by trailrider894
Did you do a proper break in, including the heat cycles and all???

bahaha, that's definetly not the cause. u can freshly build a motor and go run the hell out of it and it won't cause no trouble.

the main thing about break ins, is to make sure you change your oil after you do the first ride.

other than that, there is no need to heat cycle the gaskets or anything, once that motor warms up and runs good, you are good to go.

i love the guys who try to claim a piston or wring blows because of an improper break in. if you put the motor together right, it will be ready to run, there no break in technique that truly saves you from issues.

your issue sounds like something external.