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Post by brinkkl2000 on Jul 18, 2016 15:24:41 GMT -5
I have another troublesome scoot. It is a 50cc 4 stroke, gy6 I believe. With a lot of cranking and some throttle manipulation I can get it to run and it sounds pretty solid, but it wont idle. I don't hear any noises. The first time I tried to turn it over, the crank was solid, thought it was seized. Found out it was badly hydrolocked. First time I had seen a scoot with a crankcase full of gas. I drained it all out, pulled the plug and kicked her over until it was clean. Popped a new plug in, fresh gas, fresh oil, adjusted valves, new carb. Compression is over 100. If I have it running and let go of the throttle she dies right out. Takes a while to get started again, and then will die if I let of the throttle. Any ideas? Would the gas in the oil caused any bottom end issues that I am not seeing?
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Post by tortoise on Jul 18, 2016 15:41:37 GMT -5
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Post by brinkkl2000 on Jul 18, 2016 15:44:13 GMT -5
How did he having it running off a vacuum operated diaphragm with the vacuum line plugged?
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Post by cyborg on Jul 18, 2016 16:47:41 GMT -5
Float in carb stuck open,,, constant flood of fuel,,, and vacuum fuel tap may be bad as well flowing fuel when no vacuum
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Post by lain on Jul 18, 2016 18:41:52 GMT -5
If it was hydrolocked, and the previous owner tried to do a bunch of crap to it in that condition it could have some lightly damaged rings. Does it smoke when you are able to get it to run?
Unless you have some funky setup, fuel going to the vent or something instead of to the carb, the only way fuel can get into the oil is to pass by the piston.
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Post by brinkkl2000 on Jul 18, 2016 19:51:48 GMT -5
Thanks for the replies. Yes it was smoking while it was running. Not bad, but more than I have seen out of any scooters I have worked on in the past. I have seen many engines with gas in the oil, but never that have a fuel cutoff, ie the vacuum petcock. I was hoping the rings weren't damaged but was afraid the smoke was telling me different which is why I did the compression test at around 105. Can the vacuum petcock on these scooters be bypassed? I have never tried it before.
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Post by cyborg on Jul 18, 2016 20:03:08 GMT -5
how many miles on the beast?
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Post by lain on Jul 18, 2016 20:03:14 GMT -5
Yeah with a manual one. Just remember to close it when not in use. Or for a short term quick rig macguyver type thing, suck on the tube of the vacuum hose while connected to the petcock, while holding your breath (but don't inhale from the hose) bend the hose and tie it tight with a couple zipties. This will make the petcock stay open until the pressure is released.
Smoke is not normal for a 4 stroke except after storage, could just be that if it's sat for a while with gas in the chamber. If it runs off later and stops smoking later in the game you'd know it's just that.
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Post by tortoise on Jul 18, 2016 20:59:47 GMT -5
For testing purposes . . if the petcock is the frame mounted type (as in the video), connect the inlet and outlet lines with a section of ink tube from a ball point pen, and plug/pinch the vacuum line. If working properly, the carb fuel bowl float-valve should stop inlet flow.
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Post by brinkkl2000 on Jul 19, 2016 9:30:21 GMT -5
Petcock seemed to be it. I pulled the vacuum line off this morning and there was fuel coming out of it, swapped it out with another I had lying around and it fired up and idled! Thank you, don't know if I ever would have looked there.
Another problem though, the rear wheel will not stop moving no matter how low the idle is. If I grab the brake, the engine stalls. Also when I rev it up, the rpm hangs, tried adjusting the fuel screw with no changes.
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Post by tortoise on Jul 19, 2016 11:00:03 GMT -5
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Post by brinkkl2000 on Jul 20, 2016 13:41:41 GMT -5
Haven't had a chance to dig back in to it, but my customer called and I explained what was going on and lo and behold they told me they put a new drive belt on. I am thinking they got the wrong one. Are these belts fairly universal or do I need to find the one for this specific model scoot? I don't think I have ever had to look for a very specific part, its all been pretty generic so far
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Post by lain on Jul 20, 2016 15:39:05 GMT -5
Kind of generic, gotta buy quality though and the right size. Possible they got a size that's too short. What size case, wheel, etc? You're gonna have to look into it a little to find the size for it to make sure it's correct. Could also be improper installation. Should also think about the cause of the bet breaking, because THAT may be the actual cause of all the frustration. A broken clutch that won't disengage could cause that too. So many things sound like another problem till you get down to taking it apart and checking parts.
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Post by brinkkl2000 on Jul 21, 2016 9:22:06 GMT -5
So I pulled the cover, and as I was expecting to see, the belt was extremely tight. So tight I don't know how they got it on. I have here a 50cc 4 stroke with a 10" rim (2003 Manco Hornet), which according to my research is a short case and shows I need a 669-18.1-30 belt. The belt I pulled off says it is a Gates Powerlink 669-18.1, that's it no other numbers. I would expect to see a 30 behing the 18.1, but there is nothing there. I don't want to order another belt and have be this exact same one. Is "30" the length in inches? If so, this one measures about 26.5 around the outside of the belt. I think I am getting close here, just don't want to order the same thing I have.
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Post by brinkkl2000 on Jul 25, 2016 11:42:17 GMT -5
Thanks for all the tips and direction everyone. I figured for the 50 bucks it was for parts I would just get a new variator and driven clutch. Scooter runs pretty good now, not perfect but 100% better than it was. It was the correct belt too, I just never took notice before of how tight they were.
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