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Very loud noise when starting and then nothing

Discussion in 'Technical and Troubleshooting Torque' started by spada89, Mar 28, 2012.

  1. G'day,

    Three times in the last month or so, on starting the bike, there is a very loud noise from the crankcase area, I think.

    Immediately afterwards, the starter just does not work after that.

    The battery is fine ( 6 months old and right capacity). Thumbing the starter button does nothing.

    I have to then put the bike into gear, rock it backwards and forwards and thumb the starter while pulling in the clutch. The Bike starts no problems.

    I initially thought it was a short as it happened after heavy rain the first time. But the lights and horn were fine. I was going to park it and take the train back when I accidentally pushed it into gear and discovered the above mentioned "rocking the bike in gear" method worked.

    The bike is a 1988 Spada in good nick. No issues with the gear box. Maintained well.

    Can someone enlighten me? What could be the issue?

    I don't want a surprise when I get to my mechanic.

    Thanks in Advance, OR
  2. Starter clutch?
    • Like Like x 1
  3. This. At least as first suspect.
  4. @PatB and Titus

    Thank you very much. I didn't realise there was a starter clutch and that it needs replacement. My scary thought was a broken tooth or something.

    Is repairing this very expensive? does the entire gearbox need to be taken apart?

    Thanks again. Much appreciate your help, OR
  5. Absolutely what they said. The starter motor hangs off the front of the engine and is easily accessible on the Spada. You won't have to dismantle anything.
    Not sure of the price but it's a relatively cheap one - parts are definitely available...
  6. If I remember correctly from the last time I pulled down a VT250, some 20 years ago...

    I'm inclined to think the starter brushes are worn, if there's no starter noise at all.

    Rocking the bike is seating the brushes again and gives you another chance... for a while.

    The starter clutch is engaged when the the revs are zero to low, so the starter rotor turns with the transmission and crank when you're doing the rock'n'roll thing.

    When the engine starts the revs increase enough that the starter clutch disengages and the starter rotor returns to rest. When the engine revs drop low enough, when you kill the engine, the starter clutch engages again... which is why you hear some bikes starter motor whine when you turn their engine off.

    If the starter clutch was shot (or stuck in the disengaged position) and the starter motor was good, you would hear the motor running at full speed... whining its tit off.
  7. Stater clutch, yeah, maybe, except for the loud noise from the crankcase......from my experience it COULD also be hydraulic lock. I had a GPZ900R that did the same thing, ended up being what is called hydraulic lock of the ignition chamber. This is when your fuel tap leaks overnight and fills the ignition chamber completely. When you turn the bike over in the morning the piston can't move because the bore is full of fuel and the motor makes a horrible metal on metal sound. Rocking the bike in gear is the only way to open up a valve and expel the fuel. This happenend to me about 3 times before the motor blew up, the hydraulic lock had fatigued a conrod which snapped in half and absolutely destroyed the motor at about 5000rpm or so, luckily nothing locked up, my lucky day......sort of. A vacuum fuel tap was the cause, these do not have, or didn't in those days, an off position, only on and reserve. I suggest you see if this is the case, if so, remove your fuel line from the tank and see if the tap leaks, being vacuum operated it shouldn't leak at all. If it does leak then my advice is don't start the bike again until you get the tap changed. I hope I'm wrong for your sake, good luck
  8. Good call Newty,

    he could take the spark plugs out over night also... to prove if a/the cyclinder/s are filling with petrol. The bike would also stink of petrol and the oil would likely too as it will run down the bore/s to the sump.

    If the engine was in hydraulic lock, you would hear the starter relay click and maybe also get some noise from the starter gears as the lash was taken up... either way the starter would still be drawing lots of current, this could be tested with a temporary fuse link (of moderately low value) on the starter cable. The starter motor would also start to get warm.

    Another possibility, easy and cheap to fix, is that there is a poor connection on the high current cables to the starter motor - battery - relay. When you press the starter button, the relay makes the high current connection, the motor is sitting on a compression stroke and all that results is a small rotation of the crank before the the piston stops because the starter can't get enough current to produce enough torque to overcome the compression. The more you try to press the start button the less that happens because the poor connection gets warmer (hot even) and the connection gets worse. When you rock'n'roll the bike you're getting the engine off the compression stroke and the motor is able to produce enough momentum to overcome the compression stoke. It's easy to disconnect, check, clean, and reconnect the cables.

    There's a few things it might be, eliminate the cheap and easy ones first.
  9. Spada89, try to describe the noise (apart from it being loud).
  10. Thanks to all of you helpful folks.

    @Newty - Hydraulic Lock may be the most probable cause.

    I did not connect my leaking fuel tap with this problem

    A month or so ago, my fuel tap was leaking and Chivos@Granville couldn't find the part. The apprentice told me he put in a bung of some sort till he found the vacuum disk part thingy.

    The Hydraulic lock seem probable because of the horrible metal sound like two things hitting each other.

    Why would the conrod fail? The piston rings should hold and petrol should not flow into the crankcase.

    Today morning the same thing happened and after rocking the bike a couple of time the bike started but with a lot of smoke like an over rich 2-stroke.

    Thanks for the explanation re opening the valve. That is why the bike starts after I rock the bike in gear.

    The more I think about it and with all your help, it doesn't seem like the starter as the bike starts beautifully after a short ride.

    Must get to Steve Wyers (Caringbah) and get my fuel tap changed ASAP. Bought the bike from him.

    Any other suggestions for buying a cheap SPADA fuel tap are very welcome.

    Thanks everyone, OR

  11. When the bike is cold the piston rings don't actually seal the chamber 100%, they are given a tolerance so everything can expand and seal nicely when the engine is warm. No doubt if hydraulic lock was taking place some (very little) fuel would have made its way down the bore and into your oil, i would recommend changing it. I've heard some good stories of exploding crankcase but that's pretty extreme cases :p. Conrods fail because the engine is literally "locked" and well you heard of the weakest link?

    But make sure you confirm this is the cause before you start throwing money at it.

    Edit: Also if this is the problem don't continue starting the bike like this, petrol washes the bore of oil "bore wash", every time your starting your bike there is no oil on the bores and the piston/bore are scuffing
  12. @Ampto

    Thanks for the Engineering refresher. Much appreciate your advice. It is going straight to Caringbah tomorrow morning.

    Cheers, OR
  13. Sorry to bring up an old post spada89, but I was wondering what was the solution to your problem? I have a spada as well, and the starter clutch is currently being replaced. Just wondering, as I'm trying to learn as much as possible. Cheers.
  14. @rorschach - My apologies for the delay in responding. I was traveling.

    The issue was fuel leaking past the piston rings. Thanks Newty and Ampto.

    I got a second hand fuel kit from the wreckers and changed it myself. No problems since then.

    Thanks everyone. Bike is as good as new and serves me well in the traffic.

    Regards, OR