A high pitched sound is often bearings. As for which ones, here's one of my old mechanics tricks- Place the tip of a screwdriver directly on the metal case near where you think the noise is coming from, and the other end of the screwdriver directly on your ear, right on the little thing that folds in over your ear canal. Push down hard and you will be able to hear what's going on in the motor. I know it sounds funny, but it works. And yes, I've spent years rebuilding everything from Caterpillar diesel motors to motorcycle motors. Or buy a stethoscope, which does the same thing. Once you determine where the sound comes from, you can determine the parts that are there.
Are you using the specified oil? If it's too thick, it won't flow well. Is your oil pump pumping? Any obstructions there?
This is one of those times I would be wanting to check for metal in the oil, because you may have a bad bottom end. If so, it's better to fix it now than wait for other things to be ruined. Honda motors are easy to rebuild, and the manual is online to show you how. Good luck!
--- In Honda-C70@yahoogroups.com, "A" <ak6666666@...> wrote:
>
>
> --- In Honda-C70@yahoogroups.com, "A" <ak6666666@> wrote:
> >
> > Hello everyone.
> > For 15 to 30 seconds after starting, engine gives out high pich jingling sound. Then all of a sudden this gets muffled, due to oil reaching all parts.
> >
> > Is the initial jingling period the time when there is most wear occuring in the engine? From where does this noise originate? From ring pistons or timing chain?
> >
> > New engines, which use thinner oil, have this sound coming all the time. But in my engine, the thick oil completely stops this sound after 30 seconds or so.
> >
>
> Any idea why it happens? Should I be concerned?
>
1970-73 C70 Honda Service Manual: http://tinyurl.com/6ebwtw
1970-73 C70 Troubleshooting Guide:
http://tinyurl.com/6ebwtw (scroll to sec.7.1 page 101.jpg)
1980-83 C70 Honda Service Manual: http://tinyurl.com/hu42c
1980-81 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec.18-1 page 170.jpg)
1982-83 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec. 20-28 page 205.jpg)
1980-81 C70 Maintenance Schedule: http://tinyurl.com/z4zn6
1982-83 C70 Maintenance Schedule: http://tinyurl.com/hw35c
More resources for C70 Passports and Cubs:
http://www.shlaes.com/Vehicles/Scooter.htm
http://www.velodrome.com/HondaC70/HondaC70.html
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