Engine Knock

[kwaka]

My bike ( Z1B ) has been used infrequently, and has recently developed a knocking on deceleration. Of course i have avoided riding but needed to get it to a mechanic, as i attempted to get it there to my horror a loud metallic grinding noise developed. I quickly pulled over put it in neutral and gently pushed the bike, but the grinding was still there. ready to call a tow, i pushed it on to the foot path and to my amazement the grinding noise disappeared. Any suggestions to the problem would be appreciated but i'm bracing myself for a complete strip down and rebuild.

[floydsz1]

Hi, Its very difficult to tell whats wrong without hearing it. As you were pushing it onto the footpath, you didnt bounce it up the kerb did you. Maybe a stone (or simular) was lodge between between caliper/disc or chain and engine casing etc or something simular.Does it still do it now , does it do it when engine is running and bike is on its stand .
If it does it only when wheels are going round, ie on centre stand then if its not a wheel bearing, though i dont think it will be, it could be the output shaft, Check that the front spocket is still on ok and the nut hasnt come off.
if that is ok, slacken the chain at the back wheel and then try moving the front sprocket/shaft up/down etc to see if there is any wear, also look for any bits of metal in the muck/oil etc around the front sprocket. this would indicate a knackered output shaft bearing.
also does the knocking get faster/louder the faster the wheels turn,, let me know,,
peter.

[kwaka]

Hi Peter, The engine knocking occurs all the time on deceleration however the grinding noise only just happened recently and i'm not game to ride the bike again in case i do some more damage, but at the time the bike was in neutral and as i pushed it i could hear the noise. i think as i opperated the clutch a few times the grinding disappeared. If the bike was in neutral surely it couldn't have come from the engine itself? Some one suggested it could be the clutch basket, but ive removed the plates and all seems well there or do i need to remove the basket itself to inspect properly?

[Steve Cooke]

If the bike was in neutral surely it couldn't have come from the engine itself?

The output shaft still rotates when when pushed in neutral, it does sound like it could be related to this shaft or hopefully just the sprocket, As said by Peter I would check the engine sprocket/shaft first. If this was loose it could first become evident on deacceleration as stated by a knocking sound ie. no load on the sprocket.

[kwaka]

Wow!! what a relief, I've taken the chain off and checked the front sprocket, there is a lot of movement there so i'm guessing ( and hoping )that is the main culprit. I'll start to dismantle, any tricks or hints i need to be aware of? Thanks fellas for youe collective wisdom, this forum is worth it's weight ( err MegaBytes ) in gold!!

[kwaka]

I'vetaken the sprocket and selector cover off, and yes, the output shaft bearing is totally knackered, there's even a few balls missing out of the bearing case it looks as though theyv'e disintergrated. I have two concerns, 1: are the missing bearing pieces likely to cause any problems and if so were can i look for the remnants, and secondly can the bearing be replaced easily ie. without having to split the case in two.
Thanks in advance, Fred.

[Jerry]

Sorry Fred, Bad news - the cases have to be separated to change the bearing. To be honest, it's the best way to do it, so you can check all the other bearings, and wash the debris out of the crankcase properly. The good news is you don't need to strip the top end, just take the motor out, upend it and take the lower crank case off.

[kwaka]

Curses!! Oh well i suppose i may as well go through the whole motor and give it a freshen up. Thanks again for all advice, I'm sure with the task ahead i'll have plenty more questions.

[floydsz1]

Hi Fred,
Glad you've found the problem. hopefully its not done any damage to anything else,As jerry said you can just split the crankcase from the bottom and leave the topend alone, if all was ok then maybe leave it, but as you say nows a good time to completely refresh the whole motor, Camchain/guides etc etc, its not all that common for the bearing to fail like it has, though the usual culprit is having the chain to tight so it pulls too much on the bearing, The good thing though is if you rebuild the whole engine now then it should never need doing again as long as you look after it.and you can just enjoy riding it,
cheers,

[simon gilling]

Fred
I have found the best way to get the Zed engine in & out of the frame is to lay the bike over on wooden blocks, remove the bolts and lift the frame off the engine. Good luck!
Simon

[kiwiz]

I must admit reading this thread had me a bit worried. I mentioned in an earlier thread that my J had developed a clunking sound deaccelerating at low speeds which "felt" like something in the trans department. I tightened up the drive chain and the the clunking diminished but felt that the chain tension was then too tight. Loosening it a bit led to some clunking returning but not to the original degree.

However I have a persistant small leak of engine oil from the transmisson into the sprocket area for the last 10 years! I replaced all the seals but to no avail. Replaced the sprocket ( because I assumed the sprocket ran inside the output shaft seal?). Again no effect. The engine has a significant gear whine under load which I have put down to old age but having read this thread wondered if my output bearing was on the way out.

To test could you just remove chain and see if there was sideways slop in the output drive shaft?

[floydsz1]

Hi KIWIZ
If you remove the chain there shouldn't be any movement in the shaft. apart from rotating. Even if you have fitted a new seal, as the shaft moves either up/down or back/forward it will not be able to stop the oil coming out.
It does sound like you have a dodgy bearing, if as you say it goes quiet when the chain is tight.

[kwaka]

Hi kiwiz. Mate if your output shaft bearing is on its way out, change it as soon as possible. Ive just pulled my sump and lower crank case off, and what a horror i found on the bottom of the sump and in the oil pump mesh. it was full of metal ranging from fine fillings to shards up to 10mm long. God knows what damage these have done to my motor. At the very least if you have any bearing movement at all, dont ride any further, take your sump off and inspect for any metal,

[Pigford]

A VERY IMPORTANT NOTE IS THAT THE OIL PUMP MESH IS PRONE TO GETTING BUNGED UP. IF THE ENGINE HASN'T BEEN APART FOR A FEW YEARS AND EVEN BEEN LEFT STANDING FOR LONG PERIODS, ITS WELL WORTH JUST DROPPING THE SUMP (EASY & CAN BE DONE IN FRAME) AND INSPECT & CLEAN MESH :shock: