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Post by pinkscoot on Jun 10, 2016 10:51:39 GMT -5
So I was so proud of my Hyosung i've been rebuilding I took it for a ride for coffee. On the way home It developed a loud clanking. I got home and opened the variatior and checked the sliders, all was good. But still the loud noise that just sounds bad. Here is a video can anyone help?
I also have problem that unless I let the engine warm up and I give it throttle it will rev up to about 4000rpm. If I turn it off and restart all is good. Any clues on this?
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Post by acvw74 on Jun 10, 2016 11:43:04 GMT -5
Have you checked your valve clearance? My speaker isn't great but it sounds like it is blowing back through the carb.
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Post by pinkscoot on Jun 10, 2016 11:45:51 GMT -5
Sorry I forgot to mention it's a 2 stroke, only reed valves.
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br36
Scoot Junior
Posts: 17 
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Post by br36 on Jun 10, 2016 12:24:12 GMT -5
Can you remove the belt and run on tickover to see if the noise remains?. I had a similar noise on a timing belt once and it was a strip/strand of belt that had shredded and was whipping the housing as it rotated.
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Post by 'O'Verse on Jun 10, 2016 15:22:02 GMT -5
In the video the belt looks like it's consistent with the noise. Is the noise coming more from the variator side or clutch side? Hard to tell just by looking at the video. Your belt does look loose. Might eventually need a stiffer contra spring if your belt isn't stretched.
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Post by pinkscoot on Jun 10, 2016 15:35:59 GMT -5
I pulled the variator off and still had the noise so I'm not sure it's the belt. I didn't check the flywheel but it did sound like it's coming the CVT side. I may try pulling the starter gear as well and kick starting and see if it's still there. Thanks for the suggestions.
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br36
Scoot Junior
Posts: 17
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Post by br36 on Jun 10, 2016 15:44:01 GMT -5
Can you remove the HT cap from the plug (so it won't start) and turn it over with the starter or kick start to see if it makes the noise at a low speed?
Avoiding anything that's spinning with loose clothing, hair etc, with it running, can u use a long screw driver as a 'stethoscope' at various points on the casing to pinpoint the origin? (Assume you've used that method before?......screwdriver tip on casings, handle resting in one ear)
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Post by pinkscoot on Jun 10, 2016 16:07:55 GMT -5
I have a HF stethoscope either the long probe on it I've used. I just hope it's not a bearing.
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br36
Scoot Junior
Posts: 17
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Post by br36 on Jun 10, 2016 16:22:22 GMT -5
Doesn't sound like a bearing noise at all to be honest. Sound isn't very clear on the iPhone but sounds like a clicking noise as if something is catching or a slipping gear/spline of some kind. Does it consistently increase with engine speed?
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Post by pinkscoot on Jun 10, 2016 17:55:34 GMT -5
It went away at higher speeds. Because of work I won't have a chance to get back to it until Monday and I'll try listening closer.
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Post by pinkscoot on Jun 12, 2016 13:53:20 GMT -5
I was able to look at my problem again today and looked at all of the suggestions. I took all of the variator and starter gear off and started it and still had the noise. I also played with the crank and everything felt tight and there was no abnormal play. Next I pulled the fan cover and cooling shroud figuring my final step was to pull the cylinder and look at the piston, cylinder and crank. I put my drill and a socket on the crankshaft and pulled the plug and spun it and no noise, HMMM. So I put the plug back in and kicked it again and it was quiet. So I'm thinking how could the plastic shroud make that much noise. So I put the CVT back together being careful that everything was tight. Started it up and the noise was still gone. Got the shroud back on and CVT cover on and started it up and the noise is gone for now. I'll see if it returns on a longer ride, for now its a case of taking it apart and putting it back together.
I also fixed the revving problem, I went searching deep in the library here and found a reference in Brents 90 jog build where he had the same problem and it was related to his needle height. I then thought back to when did the problem start and it was when I raised the needle. I put the needle back in the center and the problem seems to be gone.
I hope the ghosts are gone for now, I have another SF50 engine that I plan on doing a build on and this all just needs to get me through until then.
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Post by pinkscoot on Jul 19, 2016 10:30:04 GMT -5
I was able to get back to this scoot after sealing the intake better to get rid of the lean condition, it worked and it idles and revs nicely, no hanging or racing. I had discovered the Voltage R/R and feared the same CDI problem that I needed an OEM. I decided to order the $6.00 one from eBay that had the matching plugs, got it in and it works like a champ. I must say the headlights on this are very dim at idle, though I'm getting 12.8 volts, that will be the next job, go in and see whats wrong. I now have 3 of the 6 scoots running, not bad.
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Post by pinkscoot on Aug 2, 2016 19:42:30 GMT -5
After my last post I didn't feel comfortable with my set up and decided to go to gaskets on the reed cage and an o-ring on the carburetor. I got all of the Threebond cleaned of and cut myself new gaskets. Put it all back together and it runs great, tuned the Air/fuel in and got the main jet and needle right and it runs great. I think I'll move back to working on the Roughhouse and do the same and see if that solves that problem.
Thank you all for your help.
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Post by pellepan on Nov 20, 2023 9:46:30 GMT -5
Great that you got it running with the new CDI. Do you remember which bike the CDI was for, that you bought?
I also have a SF50 engine, and also a SD50 engine.
Do you still have any Hyosung running?
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