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Cam chain inspection

Discussion in 'Technical and Troubleshooting Torque' started by Haggismaen, Sep 17, 2006.

  1. Gday all,

    My bike has a tapping noise that increases in frequency as RPMs increase and remains audible throughout the rev range. The noise is present in neutral or gear, clutch in or out and stops as soon as the engine is switched off (tested this going down the driveway, in gear). Have already checked the valves twice so this shouldn't be the cause.

    I'm just wondering how you inspect a cam chain for damage? I've checked the cam chain tensioner and according to the manual it's operating fine, the CCT slipper and cam chain guides both look fine, no wear or damage. I can't remove the entire cam chain to take a look (still attached to the crankshaft sprocket) so I was wondering how can I tell if it is the cam chain that is causing the problem?
  2. without hearing the sound myself its hard to tell.
    unless you can see scuff marks on the chain itself, the only other way (i know of) is to remove the chain and bend it sideways to see how much sag there is and then compare to the critical limits in the manual.
    dont forget the bearings, bottom end, crankshaft etc can make interesting noises when they begin to fail.
    when you say you checked your valves, do you mean tappets?
  3. Yes, I shouldve said 'checked valve clearances'. Dissembling the entire head to check on condition of valves is something perhaps a bit beyond my ability, though if it was a warped valve I would give it a crack.

    I got a mechanic's stethoscope to see if I could isolate the noise but no real joy, whole bunch of tapping and other noises from various exposed points of the cylinders but nothing that made me go 'Eureka! There it is!'. I expected it to stick out like dog's balls with the stethoscope, but perhaps I just need someone who's ear is more trained than mine.
  4. try, with the tappet cover off and spark plugs removed, to rotate the engine by hand (either whack it on a centrestand and roll the back wheel over in gear, or remove the side cover and turn the big nut) and see if there is any frozen links in the chain, sticky bits or abnormalities. also, you can see the entire cam gear and inspect for damage. also have a look at the valves in action.
    if you still see nothing, consult your nearest doctor :grin:
  5. Thanks Joel, I'll try that when I reinstall the cams, sprocket, tensioner etc, it sounds like the best way to check the entire length of chain.

    Just wish I knew what was causing the noise, I'm not one to give up and take it to the mechanic if I can fix it myself with a bit of time and effort, but not having much mechanical experience sure hampers diagnostic efforts!
  6. does the noise change at all with the clutch in or out?

    and don't forget to follow the camshaft tightening order, torque settings and double check everything when reinstalling.

    good luck
  7. The noise decreases in frequency at the same (as far as I can tell) rate as RPMs when the clutch is pulled in when travelling down the road.
  8. Allright...putting it all back together. On the cam chain sprockets there are timing marks that you align with the top of the cylinder.

    However I can't quite get both marks (on each sprocket) aligned just right. Once the chain is applied to the sprockets the marks are off (either too high/low on one of each sprocket), if I move the chain just one tooth forward or backward then its off in the other direction, no sweet middle ground.

    I'm at a loss as to how to align them exactly and I assume it has to be spot on so that the valve timing is correct.

  9. well if both camshaft sprockets are at the correct timing marks while the chain is off, the only other thing that can be changing this is the crankshaft position?

    hope this helps, goodluck
  10. rotate the motor over (with the chain off) 180 degree's and try again.

    180 degree's out shouldnt muck up your timing as a twin cylinders of this model fire/spark on both compression and exhaust.
    make sure you have the sidecover off and allign the TDC marks on the alternator though......

    you do have the manual dont you? i am too lazy to scroll up :rofl:
  11. the most likely cause for your cam timing marks not to line up will be the crank slights off top dead centre, put the gears on close as you can get em and get your tool onto the crank and move it whichever way it takes to line the gears up that final bit. ( it should take sweet F/A )
    if it came off that way itll go back together try that before you go spinning it 180 degrees.
  12. Cantride's suggestion sounds like the most promising.

    According to the marks on the timing hole it's at the right position (TDC on the rear cylinder compression stroke in order to install the cams on the front) and the cam lobe position and timing marks on the rear cylinder confirm it.

    But if I was to turn the crank just a small amount to change the position of the cam chain in order to align the marks perfectly in the front cylinder wouldn't the timing no longer be correct as the marks would no longer match for both cylinders (all marks matching up while rear at TDC indicates correct valve timing according to the service manual).
  13. the way i do it, is to put the crank at TDC according to the rear cylinder, and then install cam gear and chain with the cam gear exactly level.

    when saying to rotate 180 degree's i assume you have done it in this order and have had no success, it goes with the theory of "a change of scenery..."

    good luck
  14. Are you using a new chain? I wouldn't worry if the gears are a TINY amount off, maybe one or two degrees at the most. If you have a choice, more advanced equals more bottom end, and retarded more top end.
    The old Kawasakis would go as much as 4 degrees out when the cam chain stretched, which is why they would end up going harder on the top end and get cranky at low rpms.

    Regards, Andrew.
  15. You should probably get a manual for it though you can alighn cams without marks.

    You are looking at cam lobe positions on TDC of fireing and exaust.

    The piston fireing will have both inlet/exaust lobes faceing up, the centre point between the 2 lobes are vertical with the lobes evenly faceing outwards.

    The cylinder between fireings will be rocking evenly on the exaust/inlet lobes.

    Being out by just one tooth can be catastrophic but is fairly easy to see lobes out of square when not correct.

    This may be hard to understand but I can't explain it much better. Sadly you may still not have found the prob. Good luck any way.
  16. Well, fixed the timing problem (I think) as the hesitation and difficulty starting has disappeared (beware the VTR250 service manual lies! When reinstalling the front cylinder camshafts the rear cylinder must be at TDC on the exhaust stroke, not the compression stroke).

    Bike purred easily to life, idled fine and revved cleanly. However while revving (or at least highly noticeable while revving) and under compression braking there is a high pitched whine coming from the front cylinder. Also a drastic loss in power.

    Any ideas? And by the way, thank you for all of your suggestions so far, been a great help.

    Probably going to take it into a mechanic anyway but there's no harm in trying myself...again :p.
  17. did you remove the head? if you did did you replace the gaskets? and while were on that did you replace all of the gaskets that came off? make sure you havent got any vacuum leak, ie a hose hanging off? and are you sure the timing is correct did you double triple and quadriple check it?

    if your really struggling get it to a mechanic so you dont risk any costly damage. :)
  18. Nah didn't remove the head, not that game :).

    Looks like I might be taking it into Sydney Performance Motorcycles, get it sorted once and for all.
  19. Just a question but how many kms has the bike done?

    the biggest worry i have is the valves and cam chains...nothing is wrong with them just don't want to open the engine up when it starts making the bad noises.
  20. 39,600-odd.