Worn-out crankshaft or CVT?  By  bigmac (Read 10,528 times)

Yeah I felt movement in the rod everytime. It's not something I checked though until the engine was dead. I knew it was something bad so I just rode it until it died, then took it apart as usual.

There isn't anything else in there that moves besides the oil pump. The chain goes on the crank in there.

I'm not really sure what else would make a noise like in that video you posted.

I mean you have the CVT, chain/chain tensioner, camshaft, valves/rockers, piston/cyl, crank, flywheel, oil pump and gear. Then the gearbox and shaft for the rear tire. Kickstart assembly and starter clutch.

Drum Rolllllllll........
This is Gunna be Good.....

Touche!!
Gotta love ya rollin with it..

Guess that's what happened then with the kick start that time. The spring's force seems fairly strong so the possibility that a lack of grease and/or dirt buildup could stop it from returning seemed unlikely to me.

As of now, I plan to wait and see how bad the noise gets with time. If it starts getting much noisier, I'll once again check for slack in the bearings. Perhaps I'll soon install that starter clutch that I was too late to cancel the order of and check for slack while I have the CVT cover off.

I'm still wondering why the noise seemed to be almost completely gone when I removed the drive belt. The tightness of the belt would put pressure on the shaft's left side. Assuming it's the crank bearings, are the bearings less noisy without the belt because there is less pressure on the bearings?

I was also thinking, that video I posted with a 50cc gy6 making the same noise as mine after a crankshaft replacement might still have damaged bearings. I have watched several videos about installing cranks on gy6 engines and the guy in the video always talks about cooling the shaft and heating the half of the case it fits into, otherwise it'll be too tight of a fit and forcing it in can damage the bearings which is said to be a common mistake. Maybe that's what happened in that video I posted.

I thought you put a new clutch and variator on already?

Well at least it’s running better.

In my opinion, the sound in the “Weird noise after crank replacement” video you posted doesn’t sound like anything I’ve heard from a variator before. Of course I don’t know everything though.

I’ve ridden with loose, tight, cracked, new, old, and/or half intact “v” guides and recently rode about five miles from a strangers house with 1.5 of the 3 “v” guides after my belt snapped, to get my scoot home until parts arrived.

Another thing that can happen is the inner diameter of the variator will wear over time. So it’ll have a “wobbly” effect when that happens. When you stick the approx 2in “slide bushing” (another part that probably has a different name on every part website) in there, there will be play over time. Still though, I’ve had that happen a couple times and it didn’t make a sound like in the video I mentioned above (that you posted) nor did it sound like I had a bad crank bearing.

Sometimes it’s tough to rule things out. These scoots like to throw curveballs, especially when you think you may have seen or heard it all, lol.

The noise is gone.

However, I still think I'm hearing some noise that wasn't there before. Maybe I'm just being overly alert now and think I'm hearing stuff that's actually normal. It's kind of like a low rumble sound.

I'd like to replace the variator and its slide bushing to see if that would make it quieter but can't stand the thought of doing anymore work on it at this time. The riding season is nearly over so perhaps in spring I'll get that done.