zx7 oil pump / generator chain failure

[Kwakked Up]

After some ideas on why this chain might snap and rattle itself around behind the clutch. Bastard thing has made a bit of a mess

60,000 kms on the engine, oil change and filter, then one day at Winton no problems. Went to Broadford the following day, wasn't particularly cold but on the 5th lap of the morning down the back straight oil light on, no clutch and lots of nasty noises ..... bugger.

I am in the process of figuring out what bits I need but interested in knowing what might have caused this. Don't want to put it back together have it go again.

Cheers

[zxrmad]

Unusual to say the least. I've never of this type of failure before. Have you stripped the engine? When you say 'no clutch' do mean the clutch would not disengage? What other damage have you found? Are you running an alternator? Very strange that the oil pump/ alternator drive chain would fail as there's not much load on it. I suspect that something else has happened here and caused the chain to fail.

[Kwakked Up]

Still not sure what would cause this, the only possibility I can think off is that the auto adjuster failed. Hard to see the chain breaking on its own as it is a fairly solid number and I don't see much load on it. Yes still running the alternator

When the chain snapped it took out the little splasher pipe that feeds oil onto the chain and clutch etc. Also as the oil pump is driven by the chain it was starved for oil over a short distance till I could find a safe place to stop. There are two thrust washers either side of the clutch basket which copped a hiding so am guessing they partially welded themselves to the clutch basket which may be why the clutch would not disengage.

[Mister_T]

Still not sure what would cause this, the only possibility I can think off is that the auto adjuster failed.

That would be my guess, based on experience with the CBX750 (aka "RC17") starter/alternator chain drive arrangement.

Out of curiosity, have you increased the oil pressure by washering up the pressure regulator valve? That could provide more load on your chain.

[Kwakked Up]

no, standard oil pressure.

I dismantled the adjuster and there seems to be a fair bit of wear on the shaft. It is only spring loaded so may have twisted in the barrel. I didn't notice any extra noise coming from the clutch cover area before although she is a rattly old beastie anyway.

I will throw it back together when I get the parts and see what happens

[Smitty]

.. the adjuster is the only thing that usually gives problems ( and is a prick of a thing to replace)

from memory, it uses oil pressure with the spring and if it pops out, NO oil pressure

[Kwakked Up]

The adjuster is only spring operated on these, no oil pressure. The spring seemed to be ok and it really has no where to go anyway.

I have it pretty much rebuilt just waiting on new clutch plates, springs etc. Still really haven't figured out the cause but will get it back together for Wakefield next week and crash test it