
September 30, 2011

Hi All.
I know one or two people have been interested to know the purpose of the stuffer plates on the crank of the Bantam and if they really made any difference to performance.
I had to remove them on my D14 as they were starting to get loose. I mentioned this in a past thread that I have linked below.
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The question was, has it made any difference?
I have just got back from a 60 mile ride and think that the difference is minimal, if any.
Down hill I got a clock reading of 70 MPH and going up the same hill 50 MPH. That is exactly the same as it was before I removed the stuffer plates.
The only small difference that I noticed is that it is slightly more jerky on over run, that may be a bit subjective as I was just looking for problems.
I am happy with the way it runs just now, so those plates won't be going back on.
Mike.

June 23, 2013


September 30, 2011

Yes that's a good point there Cocorico. I was of course referring to the flywheel plates. Quite a bad choice of words there on my part.
As you say stuffer plates would be fitted in the crankcase.
So in future we should refer to the plates that give us problems when the become detached as flywheel plates nor stuffer plates.
Do we all agree??
Mike.

July 1, 2018

Gonna have to get a dyno test set up to determine once and for all.As said previously though it would have to be the same engine with and without.From my own experience the crank I repaired and had plates on felt a little torquier??? Low down compared to the one in the bike at the moment only thing is the one at the moment has a lighter conrod and piston by about 3 ounces plus the crank itself is considerably lighter.It does like to rev quite a bit more than the other make of that what you will.
What's 7/16 in mm again?

January 9, 2013

so iv just gon to the add/info & carnt find any that give a good top speed refrance thay do miles per Galen [mpg ] & as we are serpos to keep within the speed linit wed usly not be doing much moor than 45 mph back in the hayday and even today on Derv or Petrol locomoiton gasflow & mpg go hand in hand

November 16, 2011

Bantams are hardy, adaptable creatures, only c*ckroaches & them will survive after we`ve all been nuked. I`ve been leaving out flywheel cover plates for over four decades on my own Bantams, and then on seeing they came to no harm, very soon thereafter on the ones built for others, and have never noticed any difference in running/performance....with v without.
Just make sure all rivets are removed/dealt with, if going down the sans cover plates route.
Weirdest Bantam adaptable experience was running a flat-topped three-ring piston in a D14, with not only nothing lost on top-end performance, but considerably cooler and smoother running.....all that considering much lower compression ratio, supposed poorer combustion and more friction!

November 6, 2016

It is my understanding that there comes a point, reasonably high in the rev range when crankcase pressure drops to zero - at this point the power drops away. The side plates on the crankshaft serve to maintain crankcase pressure a little further up the rev range and thus enable higher revs to be sustained and thus power to be available to pull higher revs. This was explained to me by a 2T racer (Yamaha) a long time ago.
I, therefore, think that these side plates do little for performance until you start to crack on the revs - if you like to ride with your hair on fire then you will no doubt appreciate the extra revs giving you about 5 mph more in each gear possibly 6 mph in top. Obviously this might make all the difference to a racer.
I have also heard a plausible theory - backed up by BSA literature, that the crank side plates offer less resistance to the airflow ( read fuel and oil mixture/mist flow) through the bottom end of the engine and thus more oil gets to the top end via the transfer ports. The theory gives us to understand that without the side plates more of the oil is deposited on the crankshaft webs - especially whilst the engine is warming up - and less gets upstairs where it is needed to cool and lubricate the bore. As evidence for this please note that the D7 had no crank side plates as standard but it did have an extra piston ring to give it 3 rings - one of the jobs of a piston ring is to transfer heat from the piston to the bore.
I have certainly noticed that my engines that do not enjoy side plates anymore (mainly because they are items unavailablum nowadays - otherwise I would fit them) tend to run a bit hotter than they should and as for the rev range - well I don't ride like a mainiac anymore so I don't rightly know. Given the choice, and if I could get my hands on some, I would fit them - then there can be no argument can there ? However somebody with access to a laser cutter needs to start manufacturing them - I bet they would fly off the shelves. I would certainly place an order for some B175 side plates.
Sponge
If Spacedmarine is going to do a dyno test with his D14/4 it would be very interesting to test the above assertion with some science. Bring it on because it is a question that has been haunting me for years.
Sponge said
Given the choice, and if I could get my hands on some, I would fit them - then there can be no argument can there ? However somebody with access to a laser cutter needs to start manufacturing them - I bet they would fly off the shelves.
Some on Ebay, bit expressive seeing as most people are throwing them away you could try a cheeky offer
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the Villiers 9e Kart racing engine had full circle cranks
D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

July 1, 2018

Youd only need a couple of holesaws and some sheet steel easy peasy..I've got 4 hanging around 2 aren't so bad 2 are a bit chewed up.looking at them they're slightly different makes me wonder what vintage my crank is?
One set is slightly thicker with a recess.They were the originals,the others off the second hand crank I got
What's 7/16 in mm again?

April 16, 2020

Hi All,
As a lad I used to go riding on a 51 D1 with a friend on a Norman with a 9d engine.
The Bantam we all know about, the Norman engine was I think a 125 with a
bob weight crank and a deflector top piston. On the flat and down hill the bantam
would march away but up hill the Norman would pull ahead. Was it the crank or crank plus piston?
(If you have one of those Normans I want it , OK)
Nick.
It was bigger than that
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