There
has been much unhappiness with the havoc caused by increasing
percentages of ethanol in the petrol. Owners who have sealed old petrol
tanks with proprietary tank lining liquids, have found it reacting to
the ethanol, whilst petrol taps and lines having been adversely effected
also. The
oil companies blend oil stock from different oilfields round the world
to arrive at the biggest volume of acceptable fuel. It is hardly
surprising that as the price of crude oil stock rises, they will look to
see what cheaper liquids they can mix with it to increase their profit
margins. Think of it like drug dealers who “cut” cocaine for the street
users, but the oil company executives wear suits not hoods. What
is all this about? Well just to focus on the fact that we accept fuel
as being of consistent performance but this is questionable. Early
in 2011, I rebuilt the Scott racer engine with a different block and
pistons that just had a small increase in capacity from 640cc to 680cc.
The previous block and pistons to go towards the Silk Scott project.The
engine ran rough and seized. I knew it had been OK last year, so I
measured all features of the latest and last years block and pistons and
found them to be exactly identical in all except the small increase in
capacity. The
only aspect I had not investigated was the fuel. As my racer is a test
bed for all upgrades that I subsequently incorporate to lesser degree
into customers engines, I am almost unique in Vintage Racing, in that I
run on pump fuel. I had used premium unleaded from a major brand with
no problem for years.I
knew that Vintage and Classic car enthusiasts had arranged for a
network of garages across the UK to still sell the old Four Star leaded
petrol. I discussed the subject with the owner of such a garage and he
said that he uses the Four Star fuel in all his classic cars and vows
they run much better on it. I did some research on the internet and
learned that Premium Unleaded is 96.8 octane, whereas Four Star leaded
is 98 octane. I then looked at octane boosters and found a site which
gave not just opinion, but results of octane improvements from tests on a
Ricardo octane test machine which is an industry standard. Of the
products tested, the best improvement was gained using an Australian
product known as NF, which gave 2 RON octane points.I
bought cans of the Four Star Leaded and added the NF octane booster and
LO! The engine ran very smoothly, and powerfully, did not overheat and
from observation, uses noticeably less fuel when racing. I was a happy
boy!
Now
before you all think of doing likewise, let me put records straight and
remind you that my engine is in a much higher state of tune than a
normal Scott. A standard 600cc long stroke Scott engine in new
condition gives about 19bhp on an engine dyno. I have original Scott
dyno graphs to verify this. An engine tuned by Scott’s for the TT gave
about 26bhp. If I do basic gas flow work with a contoured cylinder
head, the engine gives about 28/29 bhp, but this is with an original
exhaust system. Now add a resonant exhaust system courtesy of Mr Kardens
research on V1 ram jet engines refined for the racing MZ two strokes
and we have arrived at 42bhp at the rear wheel, which I would guess to
be about 45bhp at the crank. The fuel problems tell me that the
combustion chamber volume at 26cc is on the lower limit with the
current set up.
For anyone interested in details, Contact me.
It
is no surprise that the increase in power brings to light certain new
problems. A few years ago, I was having clutch problems as the drive
tangs were deformed by the load making the plates jam and not release
properly. Clutch
drag was a big problem. Here I would explain that clutch plates are
produced with press tools and these expensive tools last much longer if
the steel they are cutting is reasonably soft. All well and good for
the manufacturer, but clutch tangs need to be tough and so they do not
last well. We were all taught at school the law of force x distance so
it is evident that the tangs on the plain plates which engage in the
slots in the central clutch hub, will take much more load than the tangs
of the friction plates whose outer tangs are on a much bigger radius.
For my racer, I made plain friction plates laser cut from 3/32” thick
gauge plate, which is not only a tough steel naturally, but the action
of the laser cutting beam tends to harden the edges of the cut. The tangs of the plain plates in Gauge Plate are as good now as they were when installed at least ten years ago. The
tangs on the friction plates made of soft steel are being rapidly
deformed and unless the clutch is dismantled regularly and the
deformation filed up to restore working clearance, clutch drag again
rears it’s ugly head.
The solution is obvious, get some plain plates laser cut in Gauge Plate and bond on the friction discs. Ted
Hills has drawn these all up and as we only have one more meeting in
2011 (Cadwell Sept 24/25) we will get this done over the winter.
Having
finally sorted the fuel problem, we were restored to the usual
impressive reliability, so how about race meetings. I have for years
attended the Beezumph event run by the Triumph Trident and BSA Rocket
Three owners club. I enjoy pitting the Scott against the Triples of the
1970’s and the Scott has assumed the status of the Regimental Goat at
these meetings. In 2011, they ran this event at the Anglesey circuit
and I had great fun riding underneath the bigger bikes on the corners.
At the end of the event, the bikes are lined up for judging and although
my bike was not a Triple, I was asked to put it in the line up of
“Works” competition machines from the Anglo American Trans Atlantic
Match Races of the 70’s. The prize for best competition machine was
awarded to the Scott and presented by Dave Aldana who as one of the
original American team, had flown over specially for the event. This
year, the Beezumph was at the Anglesey circuit on July 29th & 30th, BUT the VMCC British Historic Racing races at Lydden near Dover were on July 30th & 31st
I agonised over this but decided that I must attend both, but would drive to Anglesey and ride on Friday 29th,
then drive to Lydden for the Vintage meeting. My son Richard is
heavily involved in the development of a new business in Devon and has
no time or facilities to fettle his bike. We agreed that he would ride
on the Saturday and I on the Sunday. Richard rode really well and had
wins, but sadly the field of older bikes was much depleted. He so much
enjoyed the rides that we agreed he should ride on Sunday morning and I
in the afternoon as there was also an over 50’s race. I proposed to the
organisers that this was changed to a pensioners race for over 65 year
olds, but the suggestion received short shrift.
So here we are on 10th
September and I am just finishing a full Moss race engine for Reinhold
Sprenger in Austria. I must say that when you have created an engine in
it’s entirety from scratch, you could be forgiven for feeling a bit
proud. I can claim to be a genuine OEM engine builder and if you build
for others no less than you would do for yourself, at least you can
sleep at night! Reinhold enjoys the Vintage races in his region and has
suggested that I join him for either the Klausen or the Grossglockner
events in 2012. His engine will breathe well and give a minimum of 30%
power uplift, but to gain more, you need a “Helpful” exhaust system.
As
Regards exhaust systems, My son Richard gets married on October 2ed and
has asked me to be his “Best Man” I can think of no greater compliment
to a father than this and am honoured. Of course the wish to contribute
a wedding present presented a puzzle. I phoned Richard’s fiancée and
asked if a present that was of more significance to Richard would be
acceptable---- Yes, They are getting a new exhaust system for Richards
bike made by Gibsons Exhausts. I spoke to Tony at Gibsons and re
recalled fondly how Dobsy went to see them to get a system for his Gold
Star, but spent most of the time telling how much he enjoyed riding the
Scott.
Tony
said that he and his partner very much liked twin two strokes and rode
Yamaha RD350YPVS bikes on the road. I also have one of these and am
sure Alfred would smile at the proof that Imitation is the most sincere
form of flattery. Whilst talking to Tony, I suggested that we consider
if an exhaust system for a road going Scott could be designed that would
release some of the untapped latent potential of the Scott engine and
yet be acceptable in outward appearance. We never stop thinking how we
can help owners and ensure future support for these remarkable Scotts.
One thing is sure, no more Scotts will ever be scrapped and as the bikes
that have been in store unused begin to emerge, they are being brought
back to life.
One
of the biggest problems looming in the future is pistons. We have been
lucky to have been given a genuine Hepolite drawing of the Silk piston
and Ted Hills has redrawn this on CAD. Once we had this, Ted made a
casting drawing with the inside profile 1.75mm smaller than the Silk
piston and with features to enable both long and short stroke pistons to
be made. The intended process is Investment casting, or “Lost Wax” if
you prefer, which will give an accurate inner profile and head shape.
The outside diameter will be left oversize to allow a range of sizes to
be produced. It is totally impossible to consider Hepolite style die
castings, as 1000 pieces all to a common size would be the required
order. In this case the castings could be ordered in 50’s but the next
hurdle is to pay for a mould for the wax masters. As this is all funded
from my little business, I hope customers will realise that they not
only pay for engine rebuilds or spares, but also contribute to the
production of spares such as the new iron barrel castings in both blind
and DPY pattern received recently..
I
now have less than two weeks to fettle my bike and Richard’s Scott as
we are determined to have two Scotts out at Cadwell. When I go to
Richard’s wedding in Devon, I will be taking a top rebuild engine for
Joe Hustwayte and will give a talk on Scotts to his bike club. The Silk
Scott project advances very slowly, but I now have a crankcase, barrel,
head, pistons, so we are getting nearer, but one commodity is
missing,-- time!
Kindest Regards to all
Roger