Vibration in engine

[laladownunder]

My 50 cc Kymco Agility gy6 4t got 13,000 kilometer. Done all the upgrade de restriction mods and going fine for about 7,000 kilometers. On the way to work just started to vibrate, no vibration when idle, only when picking up revs, done whole exercise without belt and still vibrating, changed timing chain tensioner with new longer shaft tensioner. Still vibrating, sound seems to come from bottom on variator side of motor block. I opened tappid cover and turned engine over by hand to check timing chain for broken links, but none broken, still vibrating, Also put in new sliders in variator, still vibrating. I got new Timing Chain, guides, tensioner, complete gasket set. Need help/idea where to go next.

[Mr. Paul]

Engine mount?

[laladownunder]

Thanks Mr Paul, As solid as can come, vibration sound seems inside

[laladownunder]

Also removed the belt, which eliminate drag and rear end vibration ( if any ) Still vibrating when reving up

[CROSSBOLT]

See if you can move crankshaft with CVT belt removed. That's up, down, fore and aft. Should be no movement.

Karl
 

[laladownunder]

Thanks Karl, done that and no up, down or sideways movement. also took the tappid cover of and started motor, oil everywhere, so oil pump working. Checked the timing chain again with the new longer timing chain tensioner and no extra movement on chain. touch the variator and immediately the cam moves.Also started motor with no variator disk and roller weights in, only the outside gear where starter pinion runs on, still vibrating.

[ole two wheels]

Have you checked the spark plug.? A misfire can cause a shutter.  Is the vibration harmonic or erratic?
Also might try removing the valve cover and rotating the engine to make sure the valves are moving and not sticking. Hope you can isolate the problem.

Mac

[CROSSBOLT]

Are there any missing blades on the variator fan? Also, please explain what you mean by "touch the variator and the cam moves."

Karl

[tortoise]

Also removed the belt, which eliminate drag and rear end vibration ( if any ) Still vibrating when reving up

Include spark plug cap inspection in your troubleshooting.

[ole two wheels]

Karl, wouldn't stuck sliders in the variator throw it out of balance?

Mac

[star667]

Best way to find where the sound is, is to get a mechanics stethoscope and listen if you can't get one of those find the longest screwdriver you have put the metal end on the bike and the other end on your ear

Usually it goes like this
Deep internal rumble: Crank or big end bearings
Taping in the head: valves or tensioners or an exhaust leak

[star667]

After re reading your post I'd check the oil see if you can see any metal

[CROSSBOLT]

Stuck sliders/rollers would do it, Mac, fer sure! Good point.

Karl

[ole two wheels]

Yelp, the stethoscope will tell you where the noise is. You can get one from Harbor Freight Tools really cheap. Good idea. You will get "some" noise from any where on the motor, when it,s running, but it's the louder noises you are looking for. You will know when you hear them.  Good luck.

Mac

[laladownunder]

Hi Mac, the vibration is harmonic and using a big screwdriver, seems noise is on variator side. I run engine without the internals of variator, no weights and pulley, just the outer pulley/ gear where starter motor kicks in for starting