Sophomore Rider
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Post by bigmac on Aug 27, 2017 10:37:42 GMT -5
The last few 3 or so times for me it was the rod bearing, so even when I checked the shafts it didn't matter. Were you able to feel movement when it was the rod bearing? I can look at mine since my top end is off and the rod is sticking out of the crankcase. I grabbed it and tried moving it forward and backward but didn't feel any looseness between it and the crankshaft. The rod can be slightly moved side-to-side but I heard that's normal. Also, since you have experience with taking the cranks out of these engines, is there anything at all you could think of that could come loose in there? In a gy6 service manual, I see a diagram of an oil pump on the flywheel side of the crankcase. It shows a gear, a washer, a nut, O-rings and bolts around the oil pump. Makes me wonder if there's any chance something is worn or has come loose around that area and is making the noise. If so, maybe it's causing oil to not get pumped to the top end as well which would explain my sudden valve oil seal failure on the cylinder head. |
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Post by onewheeldrive on Aug 30, 2017 3:52:24 GMT -5
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.
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Post by bigmac on Aug 31, 2017 19:54:41 GMT -5
Checked the oil pump but didn't see anything that appeared worn-out, loose or broken.
I've basically gone full circle here and everything has checked out.
I have a piston kit on the way and plan to rebuild the top end now since none of the crank bearings seem to have issues. I also have new valve seals coming and plan to install them on my old cylinder head which has 69mm valve stems. I don't see how my other head could be the source of the noise but will swap it out anyways.
One time my kick start lever wouldn't spring back up after being pushed down. I removed the CVT cover and found nothing wrong with its return spring. I disassembled the kick start to check everything and found nothing. I reassembled it just as it was before and it worked fine. It's like my scooter is cursed and will randomly not work for no apparent reason. Hopefully this will be the case with the weird noise.
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Post by pistonguy on Aug 31, 2017 23:07:26 GMT -5
Drum Rolllllllll........
This is Gunna be Good.....
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Post by bigmac on Sept 16, 2017 19:23:58 GMT -5
Is it fixed?......
No. It's still making that strange noise. Perhaps I'll try to get a video of it at some point so you can all hear it for yourselves.
I went about 24 miles on the first ride with lots of engine loading, engine braking and changes in rpm to get the engine break-in period started. The noise was coming and going through-out the ride but didn't appear to have any effect on performance.
I don't know what to make of it. I guess I'll just keep riding and eventually let it go out in a final blaze of glory while at full throttle down a big hill.
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Post by pistonguy on Sept 16, 2017 19:29:44 GMT -5
Is it fixed?...... No. It's still making that strange noise. Perhaps I'll try to get a video of it at some point so you can all hear it for yourselves. I went about 24 miles on the first ride with lots of engine loading, engine braking and changes in rpm to get the engine break-in period started. The noise was coming and going through-out the ride but didn't appear to have any effect on performance. I don't know what to make of it. I guess I'll just keep riding and eventually let it go out in a final blaze of glory while at full throttle down a big hill. Touche!! Gotta love ya rollin with it..  |
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Post by onewheeldrive on Sept 17, 2017 16:34:06 GMT -5
One time my kick start lever wouldn't spring back up after being pushed down. I removed the CVT cover and found nothing wrong with its return spring. I disassembled the kick start to check everything and found nothing. I reassembled it just as it was before and it worked fine. It's like my scooter is cursed and will randomly not work for no apparent reason. Hopefully this will be the case with the weird noise. It's most likely not because of the kickstart spring. It's likely either the shaft of the kickstart gear (that extends toward the variator when the lever is pressed) needs cleaned and a bit of grease, or the gear itself is chipped causing it to get stuck and not move freely. I've had both happen on separate occasions. Unless maybe yours popped out too far or something that one time only, I don't know. With that being said, I've actually had a noise that I thought, at first, may have been internal engine trouble. All I did to rid of the sound was bump the kickstart lever (not downward-- inward towards the case) a couple times with my foot when it was running, and the noise stopped. I think the kickstart gear may have been riding the variator. |
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Post by bigmac on Sept 18, 2017 18:42:11 GMT -5
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.
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Post by bigmac on Sept 30, 2017 11:37:12 GMT -5
It has gone 200 miles since the top end rebuild. I've been giving it a hard break-in and the noise isn't any worse. I'm starting to doubt it is the crankshaft after all. I also rechecked the shaft's ends for slack but felt none.
I find the noise is rarely heard at low idle speeds, such as around 1,500 rpm. Perhaps that's why the guy who uploaded the video of an engine noise like mine kept revving since it's mostly heard at higher speeds.
Two possibilities I have in mind now are either:
1: One or more of those three plastic V shaped guides that go onto the retainer plate behind the variator are too loose and are wiggling around between the retainer plate and variator.
2: The slots for the roller weights on the variator are worn along their edges so the rollers can shake around inside there more than they're suppose to.
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Post by onewheeldrive on Sept 30, 2017 15:48:36 GMT -5
I thought you put a new clutch and variator on already?
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Post by bigmac on Sept 30, 2017 22:15:19 GMT -5
The variator looked fine so I kept it on.
The belt and roller weights were replaced since I could tell for sure they had wear on them. Later, while running the engine without the belt, I noticed the noise seemed to be either gone or just barely there (couldn't tell for sure over the normal engine sounds) so I replaced the clutch.
The video I posted at the start of this thread about diagnosing gy6 engine noises said those plastic guides can break, causing abnormal noise but mine appeared intact. So they are in there making a dampener between the two parts but perhaps some looseness has formed and it's enough to create noise.
I must say though, I'm so glad this whole situation pushed me into doing that top end rebuild. I never thought I'd get my Chinese scooter to run so well. One push of the start button and it comes right on and idles great. I haven't had it stall out on me once at any stops while out on the road. Aside for the annoying noise, of course, this thing is running better than it did when I got it, about 6 years ago.
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Post by onewheeldrive on Oct 2, 2017 0:55:38 GMT -5
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.
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Post by bigmac on Oct 5, 2017 19:46:11 GMT -5
Those plastic "v" slider guide things came yesterday. I got them installed today but didn't have time to put it back together to see if the noise is gone.
Kind of a let down to hear that you haven't heard any noises before like the one in the video from a variator issue. The new "v" guides do fit much more securely to the retainer and hold it nicely within the variator compared to before. I checked for slack that could cause wobbling between the variator and that slide bushing but didn't feel any.
Hopefully tomorrow I'll get it back together and find that it's finally fixed after all this. I really don't want to have to order any more parts just to discover that they didn't fix the problem after installing them.
We're going to need another drum roll.
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Post by bigmac on Oct 6, 2017 19:06:09 GMT -5
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.
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Post by onewheeldrive on Oct 6, 2017 21:29:47 GMT -5
Good! Hopefully all is well now.
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