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Engine Knocking

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by ricktum, Mar 9, 2005.

  1. I am looking to buy an 81 Yamaha 650 Special but there is a problem with the engine in that is knocking i have not personally heard the knocking noise because the owner said he killed the engine when it first started making the noise. The way this happened is he accidentally pulled out infront of a car and missed 2nd gear to hurry up and get out of the way and over-revved the engine then that is when it started. He seems to think that he bent a rod but i think that he might have stretched it. i would like to get a second opinion because i am not a professional at troubleshooting motorcycle problems. whatever the problem is i still would like to purchase the bike and he is going to cut me a deal on it. I would also appreciate someone explaining to me what would the repair entail and about what you would think it would cost to have someone fix it or what it would cost if i were to do it. that is if the problem is what we think it is.

  2. Easiest way to find out is to rip the heads off and have a look.
    Does the knocking increase with engine speed?
    Ask Bond Girl, she has the answer. Take it to Mick, he's good at fixing stuff :D
  3. Does it happen when the engine is idling? If it doesn't, then its most likely tensioner, chain, sproket. If it does, then time to open her up!
  4. could be lots of things. Broken valve stem, busted bearing, broken rod, broken valve spring.

    Chances are the owner is understating it too, so I would avoid it unless it was reely cheep.

    I'd bank on $1000 for an easy fix, $2000 for medium & $3000 for anything that required welding etc

    Keep in mind that they are pretty old now and they wern't that popular in Aus so parts are going to be hard to find.

    Do an internet search and see how avialable parts are from oversees.