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1982 Yamaha virago xv920 Knocking Noise

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1982 Yamaha virago xv920 Knocking Noise

PostAuthor: VeryCafe » Thu Dec 21, 2017 1:26 pm

A couple of weeks ago I bought an 82 virago xv920 to convert into a cafe racer. The conversion is going very well, and I got the whole bike to be functional. I had the custom sub-frame put on with the custom leather seat, new headlight, took ugly speedo/tach off and put a single speedo on, new brake lights and turn signals... Everything was wired up, so I had to ride it. It started up beautifully, and rode beautifully for at least an hour until I got home. I parked it for a couple of hours and decided to get back on it and ride it again because I wanted to send a vid of me riding out of the driveway to my uncle, but when I started it up, there was a distinct knocking noise in the rear cylinder. Did research and found that if it rhythmically knocks while idling its usually something to do with the cam chain or the head of the engine. I suspected the automatic cam chain tensioner went bad, so I got a manual tensioner that fit the bike. I got it and screwed it in finger tight, then loosened it a little bit so I could start it up and adjust it using the noise it made. After a bit of adjusting, my dad said that he couldn't hear it, but I still could (But I wasn't sure if that noise was normal). I kept fiddling around with the manual tensioner, and the noise wasn't getting any better, and it started idling rough. When I revved, it sounded fine (aside from the knocking noise) but seemed to want to die on idle. I'm thinking I may have messed up the cam timing slightly. Any thoughts or ideas would be appreciated!

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Re: 1982 Yamaha virago xv920 Knocking Noise

PostAuthor: chrismalm » Thu Dec 21, 2017 1:56 pm

:VTF:
It's got fresh oil and filter with the filter hole pointed out, right ? Or did the PO fill it with snake oil to get the problem out of his garage into yours ? Get a mechanic's stethoscope or long screwdriver with the handle held to your ear, locate the source of the noise, and report back. Bad cams and/or rockers clatter, worn pistons & cylinders slap, loose chains rattle and bad bearings knock.

Not holding an idle can be a multitude of things like faulty charging or ignition system or dirty or improperly adjusted carbs. Check battery voltage when off, @ idle and 3k rpm. Check resistance of plug boots. Are you running a fuel filter ? Check the float levels with a clear tube per the FSM then drain the float bowls into a glass jar and inspect for silt. If you or the PO did not clean all the electrical connections, put that on your list too.
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Re: 1982 Yamaha virago xv920 Knocking Noise

PostAuthor: cf_indy » Mon Jan 29, 2018 1:55 pm

Mine knocks a bit, it is common to some degree from what I can tell. I ran across this discussion you can even find examples on youtube. Mine sounds like the one below.


viewtopic.php?f=14&t=30935

https://www.youtube.com/watch?v=ONnq8MFc3Pk
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