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Will this work?


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#1 Hughie

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Posted 07 October 2004 - 09:57 AM

PO knackered my Mini by not tightening the flywheel properly when he replaced the clutch. It worked loose and damaged the end of the crankshaft. The slot the keyed plate fits in has become worn, so allowing some movement when the plate is fitted.

My question : if I put everthing back together and tighten the s#*% out of it will it work, or am I faced with having to replace the crankshaft or even the engine, whichever is easier?

Thanks for any advice,

Steve

#2 Guess-Works.com

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Posted 07 October 2004 - 11:36 AM

As far as I'm aware the slot in the crank and flywheel are only there to locate the TDC marker on the Fylwheel with actual TDC of the Crank ( and correct balance point if the system has been balanced ) It does not provide any 'locking' force.

This I'm fairly sure of but would like second opinion as it's rather important

The locking force is provided by the tapered friction surfaces on the crank and flywheel, now if this has been damaged to the extent that, when torqued up to the correct amout the fylwheel does not fit ( ie there is any ANY play ) then I suspect your looking at a new crank and flywheel...also, DO NOT over tighten the nut as you're likely to damage the thread on the nut and once that's gone then there's no way the flywheels staying on...

This is basically something you do not want to let go when you're travelling along..as apart from totally f*****g your engine, the thought of 10kg's of toothed steel spinning 3000 rpm running riot in the engine bay you'd be lucky to get away with your life :nugget:

#3 dklawson

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Posted 07 October 2004 - 12:46 PM

I agree with Guessworks. However, before you decide that all the parts are NFG, borrow a known GOOD flywheel. Attempt to fit the good flywheel just to see if it "Might" fit and tighten up. Do not actually tighten it in place at this point. If there is too much wear on the crank tail the flywheel will likely bottom out on the C-washer. If this happens, you need a new crank and flywheel.

If, on the other hand, the good flywheel appears to get "tight", and you aren't bottomed out on the C-washer you may be able to salvage the crank. Remove the good flywheel and buy it or buy a brand new one. Then mark the entire taper with permanent marker or machinist's layout fluid (dye). Use a good, new, square, sharpening stone to carefully dress all the high spots on the crank taper down. The dye you put on the crank tail will help you locate the spots needing attention. Once you've hit all the high spots and things look reasonably clean, apply a thin film of valve lapping compound to the crank tail and hand fit the flywheel. Wring the two together like you were lapping an engine valve. Check and re-coat the tail frequently until a large portion of the tail has that "satin" lapped finish. You won't get it all satin as there will be low-spots. Aim for at least 80% of the surface to be lapped.

Clean the lapped tail and flywheel bore thoroughly. Then re-assemble all the bits as normal. Here are the LAST CAVEATs: Fit the flywheel with the primary gear, thrust washer, and C-washer on the crank. Make sure that as you torque the flywheel center bolt you DON'T bottom out on the C-washer. There needs to be clearance between the C-washer and the spotface on the flywheel. The last check is with all the clutch bits (and clutch cover) installed... pull your spark plugs out and turn the engine over by hand. Pay close attention to the ring gear and make sure it doesn't hit the clutch housing. Worn crank tapers can be cleaned up a little but excessive lapping and worn flywheel hubs allow the flywheel to move up on the crank further and further until the ring gear starts to hit. It's important that you check for C-washer and ring gear clearance before you finish putting things back together.

#4 Dan

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Posted 07 October 2004 - 07:54 PM

As above, all good stuff. And by no means......

tighten the s#*% out of it

It is a precision machine, and needs to be built properly. As has been said the flywheel fits to a taper. Its an interference fit, so once it is tight turning the bolt further just breaks things, and you could bust the flywheel if you tighten it enough.
Do check that everything is as it should be, and replace what needs replacing. If you drive it any more with a loose flywheel you could end up welding the flywheel to the crank and then you really will need to replace pretty much everything in the whole power unit. Or as DK said the flywheel could simply explode which may well solve all your problems, permanantly.
By the way, machinists fluid is called engineers blue by most people over here.

#5 cowboy

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Posted 07 October 2004 - 08:29 PM

hughie can you put up a picture of what is damaged, as the others have said, don't over tighten something, its better to change it, and will be cheaper in the long run

#6 Hughie

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Posted 07 October 2004 - 10:11 PM

Great replies, thanks. I'll post some pictures soon. As for the tightening, I really meant just ensuring it was torqued up properly. Honest!

Steve




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