2018 XC300 horrible sound?

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dzhitshard

New member
https://youtu.be/YYyDUmWL-2M

What on earth is this sound coming from?

I have not been able to get the flywheel off because of lack of acceptable tool.

I have good compression, measured by stroke resistance on the kickstarter.

The FW bolt is torqued to 40Nm but I can't check crank play or not torque until I can cobble a tool to get the FW off.

The noise is barely a flutter until the bike reaches operating temp and then it becomes horrible.
It "feels" like there is more violent vibration once the noise reaches the levels in the video.

Thank you
 
I'm guessing it's power valve or power valve linkage.

I've heard of the power valve actuating arm vibrating on the crank case.

Could also be something is loose on the power valve mechanism and the power valve is just flapping around.

First thing I would do is remove the right side power valve cover and run the engine, see what you can see.

Could also be a snapped piston ring but I doubt it as you say you have good compression. How many hours do you have on your piston kit?

It would be worth removing the exhaust and looking up the exhaust port with a torch, look at the piston/rings and also see if the power valve looks OK.

Fingers crossed it won't be anything too serious or expensive. :)

Best of luck and keep us updated. Dave.
 
60-80 hours on the piston.

I had a stick pull the wire out of the hour meter at some point and I'm not sure how long it took me to notice.
 
Go to the power valve, the linkage is suspect I had some similar issues and it was the power valve sticking closed. Just out of curiosity how many turns is your power valve at?
 
Wimpy525 said:
Go to the power valve, the linkage is suspect I had some similar issues and it was the power valve sticking closed. Just out of curiosity how many turns is your power valve at?
Click to expand...

Power delivery seems consistent through the throttle range when the noise is present. Bike also has good power delivery before the noise appears. Noise doesn't seem to appear until the bike is ridden under load for a few minutes.

IIRC the PV screw is set at 1 3/4ish as it sits.
 
Yes, the more I think about it, it sounds like something power valve related.

If it was a snapped ring you'd hear a rattle at idle.

Good luck, Dave.
 
Can't help, but love the expression on your son's face at the end!! such a typical "... why are you bothering with this, it still runs, we could be riding...??" look
 
LOL,

The video is doing the WHOOMP WHOOMP cyclic sound and vibration little justice. Especially when I was so frustrated I laid on the pipe for a solid 100yds just trying to see if I could make it let go.

That's my riding buddy's kid. He actually said something like "Holy crap, I thought that thing was going to explode coming down the logging road. What's wrong with it." My kid was gone by then but he was definitely the whatever, lets just ride guy.
 
Hopefully it's not too serious, won't cost too much time or money to fix and you'll be back on the trails again soon! :)

Keep us updated, all the best, Dave.
 
Pull the power valve cover off and the exhaust off to see what's happening. :)

Good luck, Dave.
 
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I have heard of excessive side to side play in the powervalve that can be fixed by just shimming up. The power valve linkage has an adjuster on the top. Adjust until the linkage just fits smoothly on the end of the power valve shaft with the valve fully closed. Also check that the wire retaining clip is still securely in place. If not, either clip it in properly or go looking for it if it ain't there! Most likely place is down in the engine and that's not ideal!

If all looks well, use a metal rod or screwdriver against your ear to try and locate the source of the noise. Move around the main sections of the cases sucb as clutch cover, crank ends, water pump, flywheel etc. Water pump shafts have been known to shear off or wear really badly causing the impellor to catch the inside of the casing.

Just try not to touch the HT lead. Not good but will clear stubborn ear wax.
 
If you feel a vibration with it, stop riding and tear into it.
My thoughts are loose nut on flywheel or clutch basket, or maybe the old problem of crank stuffer bolts coming loose, but in this case not locking the engine, just hitting the rod on each rotation.
Just thoughts to check... Good luck and let us know what you find!
 
Not sure what the noise is, but the pv arm lock nut was backed out all the way on my ?18 EC250 after about 10 hrs.

Whip the pipe off & have a gander behind the rhs pv cover to be sure.
 
eralha said:
wow... that is nightmare fuel! hope you find the issue, keep us posted. good luck.
Click to expand...

it was to me for sure. I love this bike like no other I've had. Says a lot since I hardly ever get attached to inanimate objects.

The noise turned out to be a left side main bearing. It lost the cage and allowed the balls to bunch up together leaving one side of the crank unsupported. That was the cyclic WHOOMP WHOOMP noise.

I never figured out why anyone would focus on the PV assemble since it doesn't rotate or do anything cyclic across all revs but it was adjusted properly and undamaged for those curious.

A small piece of the cage was stuck on the bottom of the rod, and about 1/8th was still in the bearing. Appears that most of the cage was evidently ejected out of the exhaust. no visible cylinder damage and no apparent rod or bearing damage on it. Thank the heavens

Thanks for everyone helping me brainstorm when I was too distraught to think clearly.
 
Mine started to make a rattle at 25 hrs , found left power valve retaining bolt missing and power valve assembly had been vibrating horizontally and vertically in the barrel and slogged the hole to egg shape slightly , I put a bolt in but didn't stop the rattling , pull your powervalve covers that should help !!!!
 
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