GY6 50cc Engine Noise Problem (Again) By jofos (Read 9,257 times)

[jofos]

Hey guys... Hope everyone is doing better than me!

Had a noise a while back, but it went away, and have concentrated on improving performance a bit since then. Switched air filters, bigger jet, new ignition coil/spark plug wire and plug, and upgraded CDI. (Also added a valve on the crankcase ventilator.)

Was running better. Recently noticed a clanky noise and it got worse and worse. Is starting and running fine, just has the scary noise.

I have posted a vid on utube, if you would be so kind as to take a look and a listen to better understand the issue:

The flywheel fan seems to be wobbling a bit as well... Tried to show that in the vid.

(Yes, I know it is dirty, and if you can see the oil, that is coming from the crankcase valve as best as I can tell, like 90% sure)

Any ideas?

(Already tried valve adjustment, changed gear oil, checked oil.)

[sprocket]

Looks to me like the main crank bearing on the fan side...

If you running it without the plastic fan shroud it could have overheated the engine to the point something went bad...the oil stops lubricating and the bearings fail...

[jhbietz]

I have also seen the rivets get loose that attach the flywheel to the hub. It will make a sound just like a bad connecting rod.

[jofos]

OK. Thanks so far!

Sprocket: I took off the cover to examine the fan.

Bashan: What is a "stator?"

I guess tomorrow I will take off the flywheel fan and examine more closely... (I have an impact wrench, fortunately!)

Thanks again guys!

[Bashan]

The stator is the ring of coils attached to the right side of the engine that generates AC electricity as the magnets in the flywheel spin around it.

^{Click on the above stator to learn how to remove it and the flywheel}

[jofos]

That looks pretty complicated, and I don't have the tool (the "puller" thingy...) Hmmm.

Looks like I hit a speed bump.

But, Thanks for the info! Will have to look into it further, I guess...

[jofos]

Well... I was able to get the flywheel off (it is a nice thing to have a machine shop in your barn, after all!) We made a part to get the job done.

Everything looked fine in there. No problems at all.

I am thinking there may be something terribly wrong with the oil pump. The engine runs fine and there seems to be no issues with the piston movement at all.

Any ideas? Experience? Thanks!

[Alleyoop]

Did you grab the Shaft that the FLywheel goes on and Try to move it up and down. That would tell you if the bearing is shot. It definitly is wobbling, and the shaft is as well from the Video.
Alleyoop

[jofos]

thanks Alley...

The whole assembly was tight. Seeing as how it is all mounted on the shaft, the whole thing would be movable, were that the case... It is not. Everything was solid and fit within the confines of the flywheel...

Maybe I should just ride it until it dies? (This same issue was posted a number of times on utube with no definitive answers)

[Alleyoop]

Then the problem with that shaft is the inside bearing if won't wobble from the outside bearing. The bearing that the shaft sits inside at the end of the shaft is probably the culprint then and that would make the other end the outside wobble.
Alleyoop

[jofos]

So... Can anyone suggest a course of action? Should I replace the crankshaft?

[iceman]

Apr 2, 2011 17:22:09 GMT -6 jofos said:

So... Can anyone suggest a course of action? Should I replace the crankshaft?

If it's not the woodruff key, then crankshaft has to be shot---it's either the connecting rod or the main bearings. I know that sound when I hear it.

Your oil pump won't cause a wobble like that, either way--- the crank is shot anyway...it's the sound that I hear..



Either do the rebuild or buy a new engine(or a semi-used one). If you do the rebuild, inspect every piece you take off: cam, the head(valves) cylinder, piston/rings, crankcase wear, oil pump/o-rings....everything. Use a manual when doing it, and take note of what you feel you need to replace. Look closely for scoring in the cylinder and on the piston. Keep your pieces/parts organized(even label them), because even though these engines are "simple", every piece is of importance. You'll also have to clean every little piece of metal out of your inner engine. Take your time... and think about getting a torque wrench.

Do the math and decide, after checking the overall damage, whether or not you should buy a new engine. If there is a lot of wear on everything, you may just want to buy a new engine rather than replacing everything piece by piece.

What's the number on your odometer?

[jofos]

Hey guys!

Well, I decided to go ahead and buy a new engine. I just bought this one: (At the bottom of the page)

www.scrappydogscooters.com/139QMB_50cc_Performance.html

(A GY6-80 Engine Assembly for short case 139qmb)

And, I guess I was jumping the gun a bit, because I realized after I went through the PayPal checkout that I was not 100% sure it would fit my scooter! (I know, duh!)

So, experts... Will it? I mailed Scrappydog as well with the same question, but I thought I might get an answer here more quickly.

Thanks!

[sprocket]

Yes if your original engine was a 50cc this will bolt right in place...

[iceman]

Scrappy either needs to change the picture, or offer 2 options for a long/short case, because the one in the picture of that link has a long shaft for the rear tire. Measure the length of the rear tire shaft with the wheel off. That looks pretty long, like the one they have for a longcase.

Sometimes what you see is what you get. Scroll all the way down this link and compare the two engines with his link:

www.scrappydogscooters.com/Replacement_Parts.html