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Post by knightflyer on Jan 14, 2015 15:36:57 GMT -5
So I was zooming to work when the belt broke on my TaoTao 50. Hadn't lost a belt before so wasn't sure what was happening at first (except that I was definitely losing power and speed rapidly).
Replaced the belt, but now the bike won't start. It may have over-revved when I lost the belt (I was at full power). Anyone have experience with an over-rev causing valve problems or anything? It had been having problems after some gunk got into the fuel tank (used a gas can that had been used previously for 2cycle mix). I had siphoned out the suspected bad gass, and put in some sea foam. That had seemed to clear up the rough running issue that had been caused by the gunk.
I squirted some carb cleaner in through the air intake. I just checked the clearances on the valves; top (intake?) is right on at .05mm, bottom seemed a little looser than .05 but I didn't measure to figure out what it was at or attempt to set (freezing temps = rushing things in the shop).
Any thoughts or suggestions on trying to get this thing running again would be appreciated. I tried to compression-test, but the tester I borrowed wouldn't fit the tiny spark plug hole. It does have enough compression to pass the finger test, but that doesn't really tell yah much. It acts like it wants to catch but won't. Starting fluid had no effect. It had a frozen ring problem once before, and the symptoms seem similar. Really can't afford to spend hundreds fixing it again like I did on that go.
Thanks, KF |
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Post by JerryScript on Jan 14, 2015 18:03:38 GMT -5
Did you check the starter gears for debris from the belt braking? They can get clogged, which could make the engine too hard to turn over.
Since it was just the belt braking, there should be no effect on starting, unless you did over-rev and damage something. If it sounds ok when cranking, and feels ok with the kickstarter, then follow the three things needed to run: compression (you're finger test is good enough), gas (did you try starter fluid to see if it would fire at all?), spark (shouldn't be an issue, but check for spark).
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Post by jerseyboy on Jan 14, 2015 19:04:06 GMT -5
Maybe you just knocked a wire off the coil or something when you where changing the belt.
Drain the tank all the way and dump a bottle of alcohol through it,,might have had water in that bad fuel.
Do like Gerry said,,rule spark out,then fuel flow to carb,and compression..if it still doesn't run might have sucked up some dirt into the pilot or main.
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Post by knightflyer on Jan 14, 2015 22:38:46 GMT -5
Checked spark, and I am getting a good spark. Good idea to clear out the gas, certainly couldn't hurt, especially since water would sit at the bottom and I did ride through a bit of foul weather (rain and such). A ring froze on this unit before, so I tend to suspect that. Was thinking I might put some liquid wrench in the cylinder and turn by hand for a bit. Might de-gunk something. Goofy bike...
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Post by jerseyboy on Jan 15, 2015 9:43:29 GMT -5
Yeah,,
Good spark,good fuel delivery to carb inlet,clean jets and spray ports,good compression,,should run..lol
Clean out that tank real good and check your compression...maybe you have a stuck ring causing blowby?
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Post by knightflyer on Jan 18, 2015 16:42:35 GMT -5
That's my guess at this point JB.  The lower valve, which is exhaust I believe, was out of tolerance - about .01mm vs .005mm, so nearly twice the gap it ought to be. Set that, but no change. I pulled the diaphrame out of the carb the other day, and when I twist the throttle I can see the gas spray for a second, so we appear to have good gas flow. Good spark as I said before. So... that leaves lows compression, which I don't have a way to check beyond the finger check. I've had a stuck ring before, so I'm guessing it's that again. Now I need to go find out how to pull the cylinder or piston so I can check the rings. Love Youtube...  THanks for the help guys, I'll let you know if I figure anything further out. Need to get the darn thing moved so I can get the expensive van into the garage though! ~KF |
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Post by knightflyer on Jan 18, 2015 18:28:15 GMT -5
the saga continues... Pulled off the carb, so I could look down at the valve. There was a little gas puddled down there from previous attempts to get the darn thing to start. I slowly turned it over by hand to watch the valve work, not really sure what I was expecting but... I got to watch how leaky the valve is! Yup, "seating well" is definitely not how I would describe it. May be other issues, but I can't see how it would be doing well the way that thing is leaking.
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Post by knightflyer on Jan 18, 2015 21:32:01 GMT -5
Okay, got the cylinder head off. They make it look much easier in the videos, lol. Tomorrow, I'm going to see if I can get a loaner valve tool at the parts store, and then reseat the valves. Going to try relapping the old ones, unless someone thinks that's a really bad idea? I don't think they're burned, but we'll see what they look like once I get them out of the head.
Seems like a lot of gunk on piston and in the dome with the valves? I haven't had an engine this far apart except in shop class, long, long, ago and that was a cleaned up one for school kids to repeatedly take apart and put back together.
I'm taking comfort from my first-aid instructor of some years back "You can't kill something that's already dead. So give it your best shot." We simply can't afford to sink much money into a $500 scooter right now. I can afford some new valves though, if needed. Real, professional, shop though? Ain't happening, lol.
~KF
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Post by jerseyboy on Jan 18, 2015 22:24:43 GMT -5
Good deal,, These little GY6 scooters are alot of fun to ride and work on..you could pull the head off and do a leak test,,lay the head on a flat surface and fill the combustion chamber full of WD-40 or similar,,make sure your spark plug it tight and see if any leaks out. A good lapping of those valves would be a great idea..I saw a guy on youtube install 2 new valves and lap the seats,,it was a very easy job,,and looked like alot of fun as well. Keep up posted brother!! Tom  |
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Post by jerseyboy on Jan 18, 2015 22:26:32 GMT -5
Here is the video of the guy doing the lapping.
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Post by knightflyer on Jan 19, 2015 9:54:23 GMT -5
Thanks JB! Okay, gotta get some valve compound while in town today... (we live 12 miles outside the closest major town.)
KF
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Post by jerseyboy on Jan 19, 2015 13:57:22 GMT -5
I would get some new valve seals for it too since you have it apart...cant hurt and they are cheap.
Gonna need a head gasket,and a new exhaust gasket too.The valve cover gasket can be used again,,just clean it up good and use a thin layer of RTV or shellac.
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Post by knightflyer on Feb 2, 2015 21:39:10 GMT -5
Thank you, great info! Project is at a stand-still at the moment due to lack of job. 
Supposed to go in to do paperwork with a company on Weds though, so should get some income coming in again and then I can get the parts to get this thing back into one piece. I hope.  |
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Post by william42 on Feb 3, 2015 12:37:32 GMT -5
I think you got way ahead of yourself. You're not going to have other problems just because you broke a belt, and I would think that an engine can handle a second or two of over-revving.
You mentioned that you were starting to have a problem because of bad gas. Maybe that over-revving was the catalyst that sucked something bad into your carb. There would have been a lot of vacuum involved with those kind of RPM's.
I think you just need a really good, thorough carburetor cleaning.
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Post by knightflyer on Apr 12, 2015 12:23:10 GMT -5
 This is the side of the valve rocker, which I noticed as I was about to begin reassembly... Figured this can't possibly be good! Valve rocker picSaw the big crack as I was wiping dirt and grease off it. The only plus to this project getting stalled for two months was the amount of cleanup I needed to do. That's when i saw the crack. So... off to order a part. I already seated the valves. They were very gunked up, and not sealing at all (could not pass the 'pour light oil on them with paper underneath' test). Hadn't put in an update though in a long time, so I figured I'd do this quick post. Thanks, KF |
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