11 replies to this topic

[BobHolness&theHexagons]

Model: Mini City
Year:1981
MG Metro 1275 engine

Hi I've recently bought and fitted ultralight flywheel (steel) from MiniSpeed, along with a turbo clutch assembly.

Only problem is now I get vibration when I rev, which I guess is because the flywheel isn't balanced.
I've only done a few miles in it, how much damage can this cause?

I'm tempted to go to the local garage and see if they can do something with their wheel balancer ...

Otherwise does anyone know a good machinist/mechanic who could do this in the London area ... how much does it cost?

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[Ethel]

Balancing would normally be done on all rotating parts as an assembly. I can't see it being manufactured that far out of balance so try reassembling it first.

[01smartc]

When we balance flywheels at Smart Performance we put the whole assembly onto a special crank (that we know is perfectly in balance) and then put in on the balancer. Then balancing holes (or dents) are drilled until it is in balance

Cost is £45

Chris @ Smart Performance

Edited by 01smartc, 21 September 2009 - 12:21 PM.

[Cooperman]

It's unusual for a lightweight flywheel to be far out and for use with revs up to about 6500 balancing is not absolutely necessary.
The crank, flywheel assembly and front pulley should be dynamically balanced as a complete assembly as the balancing of the flywheel will correct any minor imbalance in the crank itself.
If your engine is so rough at, say, 6000 rpm it may be an entirely different issue such as ignition or fuel distribution inside the induction system.

[bmcecosse]

If you think it's a balancing problem - stop running the engine ! It could break the crank. Can't see the point having an 'ultra lightweight' flywheel - and then NOT having the complete rotating assembly balanced! Have you already balanced the pistons and rods ?? The lighter the flywheel - the more critical it is to have everything perfectly balanced.
I assume you were joking about the wheel balancer!!

[MRA]

I would suggest that it is NOT a balancing issue but more likely to be a fitment issue..... did you lap the flywhell on to the crank tail using a very fine grinding paste ?

[Paul Wiginton]

The backplate is probably not centralised properly

Paul

[MRA]

The backplate is probably not centralised properly

Paul

But that can only happen iof there is damage or excessive wear.... as the straps self centre the backplate to the flywheel.... if the correct shoulder bolts are used

[Cooperman]

I've always wondered what the 'self-centering' tolerance is when fitting the 3 drive straps.
Balancing is not vital unless you intend using very high revs. As 'bmcecosse' says, if the vibration is that noticeable, don't run the engine any further.
Even balanced, though, the 1275 engine always seems rough above 6500 rpm. Now, the 970 engine was another matter.

[Sprocket]

The backplate is probably not centralised properly

Paul

But that can only happen iof there is damage or excessive wear.... as the straps self centre the backplate to the flywheel.... if the correct shoulder bolts are used

this looks like a verto flywheel to me, so those parts are not used on these.

The only way to really find out what the problem is is to have it balanced, you can at least then see how much run out there is while its on the machine, and get the balance to withing tollerable limits for the rpm.

[MRA]

Yes it is a Verto, and therefore will have (or should have) dowels, and no straps... the bolts will not be shouldered bolts on a verto unit... however I suggest that a good look at the inside of the taper will highlight some damage, or the crank taper.... both or either condition will NOT allow the flywheel to seat correctly and can cause premature failure due to cyclic loading and unloading (fatigue)

[BobHolness&theHexagons]

Cheers for all the responses!

Yes indeed verto.

Gonna take apart and re-assemble and see what I get, don't want to take the engine out just yet, gonna get a full rebuild when I can afford the new gearbox (SC)