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Knock Knock whos there..Gs500

Discussion in 'Technical and Troubleshooting Torque' started by Darmac, Apr 16, 2016.

  1. Hello all.
    Just got back from a nice little ride with a few other L and P platers.. the old GS was going great guns until after stopping for a break.. when taking off i could hear an intermittent knocking sound at random intervals... mainly when accelerating. I could also feel it through the foot pegs.. but it was quite random and would come and go..and the bike was still running well. Any ideas what it could be.? It sounded as if it was coming from the sump... uh-oh

  2. have you used the correct octane rated fuel - too high an octane rating can cause 'knocking' (I think it's too high that does it)
  3. The manual recommends 91 or higher.. i put 95 in it this morning and did about 100 km before the knocking began.
  4. run the tank down to a half then top up with 91 and see if it continues.

    also, suggest you read the disclaimer in my signature.
  5. Thanks.. ill give that a go.. i hope its something as simple as that.. the noise sounded pretty serious. I was getting pretty paranoid.
  6. low octane can cause pinging.

    you don't feel pinging through the pegs...
    • Agree Agree x 2
  7. Would you feel the too high octane knock through the pegs?
  8. Higher Octane Fuels will lessen the pinging/knocking. You and Old Corollas are talking about the same thing. Chiiliman64 was incorrect, had his facts backwards. Pays to read his disclaimer.
  9. pinging will likely sound like a screwdriver tapping on the head.
    knocking (like a dull hammer hitting bottom of engine) is not pinging, that's more likely to be bottom end.

    until you diagnose it, it could be anything :)
  10. Right.. gotcha.. it definitely sounded/ felt more serious than the wrong fuel.. bottom end sounds more like what i was thinking... might have to get the doctor to take a look.. crap timing if thats the case.. supposed to be sitting my P's in a couple of weeks. Thanks anyway.
  11. check your oil level first..
    keep riding and try to diagnose exactly what inputs/speed/rpm/gear are causing the noise/feeling :)
    if concerned, take it easy until P's test
  12. Oil level is good. Topped up with 91 octane as per chilliman64's advice but didnt seem to make any difference.
    So the bike is still running smooth.. no noticible difference in performance.
    The knocking was happening in all gears and throuhout the whole rev range but only under medium/hard acceleration... not while cruising or down shifting and not when idling... and no rhythm to it.. just very random... like a stone bouncing around in the sump. Thats my diagnosis...
  13. I'd get it to a mechanic before something goes bang.

    PS It isn't a loose chain banging on things?
    • Agree Agree x 1
  14. I did a rear wheel replacement on friday and re-adjusted chain tension afterward.. I'll give it another look at this afternoon... cheers.
  15. Re adjusted chain to tighter end of spec and took it for a ride... seemed to make matters worse so i re-read manual and realised i should be adjusting chain tension on center stand.. (not side stand)
    So slackened chain to spec on side stand and made a big difference.. i could still hear a slight knock in 1st and 2nd gear but seemed alot better... just hope i haven't done any lasting damage. Thanks for the advice.. i think you pointed me in the right direction.
    • Like Like x 1
  16. Also remember that chains can get tight spots. You need to test the chain in different spots and make sure you have a bit of slack at the tightest spot of the chain.
  17. Try putting the bike in neutral and holding the throttle partway open (say about 4000 rpm) with the bike stationary and on the centre stand, if you can still hear the 'knock' then it's not the drive chain.
  18. Yip. The chain isn't too badly stretched i dont think.. maybe 10mm difference from tightest section to loosest. I measured and adjusted on the tightest part of the chain.
  19. Nah.. it doesn't make any knocking noise when doing this... or idling or while cruising.. only when accelerating in gear.. im starting to thing i may have damaged the front sprocket bearing from over tightening the chain... like a nooby dipshit might.
  20. Check the front sprocket bearing, rear sprocket carrier bearing and cush drive rubbers. What condition are your chain and sprockets in? Also, put the bike on centre stand/ paddock stand, then grab the rear wheel and try moving from side to side to do a quick check on the wheel bearings.
    • Agree Agree x 1