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Post by userix on Feb 19, 2015 3:04:33 GMT -5
I was replacing my exhaust gasket and welding the header pipe and decided to look up into the exhaust port. I noticed the exhaust valve is completely white. Previously, I was riding around with a crack in my exhaust header pipe, right where it attaches to the cylinder head. I was backfiring like crazy, which prompted me to examine the exhaust pipe. Can riding around 5mi with this exhaust leak cause the exhaust valve to turn white? Does this mean my valve is damaged? Pardon the blurry pic, as I was taking the picture through the inspection mirror  |
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Post by ricardoguitars on Feb 19, 2015 7:57:59 GMT -5
You might be getting oil in the combustion chamber, looks like the white stuff the builds up on the sparkplugs when you are burning oil. Take a look at the sparkplug.  |
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Post by rcq92130 on Feb 19, 2015 8:19:19 GMT -5
Crack in the exhaust header right at the exhaust port? Popping & backfiring?
Sucking cold air back into the exhaust valve each stroke of the engine. Might have something burned or warped.
Compression test, and if OK cross your fingers and hope.
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Post by JerryScript on Feb 19, 2015 11:06:01 GMT -5
Yes, you can damage the engine by riding with a bad exhaust leak. I would pull the head and see if the exhaust valve needs lapping or replacement. If you can get by with just lapping, do both valves while your at it.
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Post by userix on Feb 20, 2015 2:18:41 GMT -5
The spark plug looks fine, nice golden brown, no where near white like the valve in the picture above.
After getting the exhaust header welded and fixed, I went for a ride, during a short WOT session, the engine all of a sudden loss power and stalled out, I thought I heard something breaking/rattling. The scooter wouldn't start after that, it would still crank and produce spark, but wouldn't start. I had it trucked back home and I examined the CVT transmission to make sure the belt and transmission components were ok. I also checked the valve gaps and both were set fine.
The following day, the scooter does start up no difficulty, but as it idles, I hear this intermittent metal knocking noise coming from the engine, as shown below in the video. I examined the transmission side to ensure everything was spinning fine and nothing was out of balance. Crankshaft is spinning true. I can still ride the scooter just fine, but it does make that metal knocking noise just like in the video. There is no loss in power or low-end torque and I did a compression test and it showed 145 PSI, so I believe compression is still good. Acceleration is good too. While I do hear the loud metal knocking noise, I don't feel any unbalanced vibration when riding.
But I know something broke during that last ride when it all of sudden died, as it didn't have this knocking sound before.
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Post by rcq92130 on Feb 20, 2015 2:41:01 GMT -5
145 is quite low.
sounds like a soft seize happened. Like JerryS said, pull the head to check valves, and then you can see if the jug is scored.
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Freshman Rider
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Post by userix on Feb 20, 2015 3:53:43 GMT -5
145 is quite low. sounds like a soft seize happened. Like JerryS said, pull the head to check valves, and then you can see if the jug is scored. What's the PSI suppose to be at for a working condition GY6? The scooter still has the same power and torque. It pulls me up hills just as well as it did before soft seizing. Do you know what that knocking noise is coming from? I suspect that is the result of the soft seize or whatever happened during that ride. |
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Post by JerryScript on Feb 20, 2015 5:56:08 GMT -5
I would pull the head and check everything out. It's hard to determine what it is from that short video, but I'm still thinking it's a valve issue. I actually rode my 50cc with a broken valve seat for several months before I finally dropped the valve into the cylinder, leaving chatter marks across the top of my piston. In my case, the top of the valve stem had sheared off:  |
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