Author Topic: D14 flywheel plates  (Read 214 times)

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Y13 Alan G

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D14 flywheel plates
« on: 02 January, 2022, 16:13:34 »
D14. I am having the crank balanced because I needed a new big end and had to have a MZ con rod as no D14 con rods available. The Mz con rod only weighs 144 grams whereas  the BSA one weighs 200 grams hence crank needs balancing as bad vibrations over 45 MPH. The flywheels have plates steel riveted their outside faces and these will have to be removed for crankshaft balancing.
My question is do these baffle plates have to be replaced after balancing or will the bike run ok without them? Any advice appreciated.

idie

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Re: D14 flywheel plates
« Reply #1 on: 02 January, 2022, 16:22:30 »
Aren't the plates there to increase crankcase compression?

JulianS

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Re: D14 flywheel plates
« Reply #2 on: 02 January, 2022, 16:42:30 »
My own experience with a D14 and a B175 is that the compression plates being removed did not make any noticable difference to the running of the bike.

Some D14 models experience reliability problems due to the plate rivets shedding and wrecking the bottom end.

See below service sheet.

The B175 cranks had the plates crimped in place and did not suffer the rivet problem.

A65ROCKET

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Re: D14 flywheel plates
« Reply #3 on: 02 January, 2022, 20:32:37 »
I too noticed no difference in power when I ran a crankshaft without stuffer plates.
I have just changed my conrod to the Rex Caunt one as well.
I didn't rebalance the crankshaft, just set up my shafts for .002" runout.
I haven't noticed any new vibrations at a different rev range (yet)

AdrianS

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Re: D14 flywheel plates
« Reply #4 on: 02 January, 2022, 21:50:53 »
Donít bother with the plates.
Can cause more problems than they are worth.
Make virtually no difference to the performance.
With regard to balancing, remember it is not just the weight of the con rod but the piston as well.
If the engineering company who fits the new con rod can balance the assembly why not let them do it?
My D14 had a new rod fitted and I just run it without any balancing and canít say I notice much difference in vibration.

Y13 Alan G

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Re: D14 flywheel plates
« Reply #5 on: 03 January, 2022, 17:51:29 »
Many thanks for all the helpful info. It confirms what I have been told that the removal of the plates makes no difference to performance.
I have heard from the BSA Bantam Forum, out of action at present, that some who fit a REX Caunt con rod have experienced quite severe vibration at speeds over 45 mph. This is exactly what has happened to my D14. I have found an engineer who knows how to remove the plates and ALL parts of the rivets and the balance the flywheels ( a disaster if you leave any bits of the rivets in the flywheels). Yes I'm sending him the piston, gudgeon pin & circlips as well as the flywheels & crank assembly. It will be some time before the work is done & I am able to rebuild the engine and take it for a test ride but I''l post the outcome in due course.