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Top end ticking/knocking

Discussion in 'The Garage' started by MrPURPL3, Sep 12, 2021.

  1. MrPURPL3

    MrPURPL3 XS400 Member

    Hello guys, I recently ran into some trouble with the bike and I am hoping someone can guide me to figure out what I can do. The bike turns on goes into gear well but once I try to throttle it, it seems unresponsive to actually move the bike beyond 30kph. I've checked and adjusted the valves and everything seems in spec, and I even used a jack to keep the engine at TDC for both cylinders. I am just wondering if I am going to have actually open the top end and be surprised with something beyond my mechanical capabilities.
     
  2. Buddha

    Buddha XS400 Addict

    Sounds like excessive rocker/valve clearance IMHO. Explain exactly how you adjusted the valves.
     
  3. MrPURPL3

    MrPURPL3 XS400 Member

    First I put the bike on the middle stand, removed the seat,tank etc., removed that stator cover, the valve view plugs and the spark plug to see the piston. I turned the crank until i reach LT and kept the breaker bar in place with the jack so it wouldn't turn back. I would check that the rockers were in free play and adjust the valve clearance to 0.08 - 0.12 mm for intake and 0.16 - 0.2 mm for exhaust (exhaust ones being the view ports that are at the top front portion of the engine). Once the LT was done I would move the crank forward until RT and repeat. Once done I just put everything together but never turn the crank again after adjusting for RT.
     
  4. Buddha

    Buddha XS400 Addict

    Sounds like you did it the way I would have. Just double check that when your on LT or RT that the cam lobes are in the TDC to fire position for each cylinder.
    Have you checked the compression as is?
     
  5. MrPURPL3

    MrPURPL3 XS400 Member

    I haven't checked compression yet and will need to by the tool to do so. For now based off what you hear I might try going tighter on the clearances by getting a diff set of feeler gauges. Would dropping down to 0.06/0.07 mm for intake for eg. be too tight of a clearance? I only ask bc we are dealing with an almost 40 year old engine, perhaps the wear on the engine requires a closer clearance than the initial specs of the 80s? Also I am going to try to be ultra super meticulous and ensuring that I am not moving back on TDC and that Im def on the firing position.
     
  6. Buddha

    Buddha XS400 Addict

    I would set the valves to spec, you shouldn't have to go tighter.
     
  7. MrPURPL3

    MrPURPL3 XS400 Member

    Hey Buddha, update on the knocking, I was able to fix it by closing the valve gap (not all the way but a couple turns on the adjustment screw) on the LH side of the engine when it was past the compression stroke. I then turned the engine forward to LH TDC and simply adjusted the valve clearance to the proper specs. Buttoned everything up and now theres no more knocking and it sounds better than did before. BUT I still have the no power issue after I put the bike in second gear, I rode it around in first and it definitely has power as I almost lifted the front end a couple times. I recently changed the oil and found a little bit of non-magnetic metal flakes. I am hoping you can guide me on where I need to make the repairs. Also I saw your xs build thread and everything you do is super well done at a very professional level.
     
  8. Buddha

    Buddha XS400 Addict

    Are you sure you're firing on both cylinders? With engine running pull spark plug cap off the L spark plug, you should notice the RPM's drop. Put it back on a and do the same for the R spark plug. If you pull the cap on either L or R and nothing happens that cylinder is not firing. If you have a cylinder thats not firing and you pull the spark plug cap off the one that is firing the engine will die.
    Also do a compression test.
     
    xschris likes this.
  9. MrPURPL3

    MrPURPL3 XS400 Member

    So both cylinders are firing and compression is really good on one side and ok in the other. 145-150 for LH and 125-130 for RH. I unplugged the caps and the bike would die right away.
     
  10. Buddha

    Buddha XS400 Addict

    You unplugged and plugged the caps one at a time correct? Not both at once
     
  11. It sounds strong, is it a carb adjustment issue?
     
  12. MrPURPL3

    MrPURPL3 XS400 Member

    Yes I unplugged one at a time. I am not sure after I successfully adjusted the valve clearance I had to adjust the idle screw down a bit as it but that was it.
     

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