Moss Engineering

33 Kings Lane
South Croxton
Leics. LE7 3RE

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Ethanol content of Petrol...

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


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New video added...

Old footage of Snetterton recently discovered and uploaded

I have met and continue to meet great people through Scotts and the drama adds zest to my life. Recently, a man named Barry Lain phoned me for some info about Scotts. He had long wanted a Scott and had seen one racing in 1986 at Snetterton which had much impressed him. He had recently found and bought both a Scott and a vintage Douglas. In 1986, he had bought a video camera and filmed a good selection of paddock and racing at a Snetterton Vintage racing event. He asked if I had ever raced at Snetterton and I told him I had, but not very often. He told me that he had filmed the Scott in the paddock with an old man sitting on it- I asked if the bike had droopy bars and carried the number 115. He answered in the affirmative. I then knew that particular event.

My dad had had a heart attack and was getting over it, but was a bit shaken and frail. I wondered if I could do something to lift his mood and decided to invite him to the next race meeting at Snetterton On the way over, he asked me if I thought I would win. To my dad, you either won, or it was a waste of time. We are quite a bit different in our outlooks! I told him that Snetterton was a track that suited bikes with a good top speed and that the Scott was not as fast as a cammy Norton for example, but I thought I would be well up. In truth, I knew the track pretty well as I had raced my Laverda and 750 Ducati production bikes there many times from 1970 onwards with the BFRC club of which I was President. My dad went to watch the race by the fence and next to him was another man who told him, “I have come specially to see the Scott, It was here last year and he will win. My dad told him that it was his son’s bike and I had told him I did not expect to win.

The first circuit saw me with a big lead and went on to win comfortably. The man told my dad that he should have more faith in his son! The video shows a great selection of bikes and is quite well filmed for an amateur, as video filming is never as easy as expected. The sound is quite good which suits the Scott as it was before it was banned for excessive noise at Oulton and obliged to wear a silenced system.

Watch the video from Snetterton 1986 coutesy of YouTube at Scott Motorcycles/Video/Racing/Snetterton or download it at ..movies/Snetterton_1986

And for for those of you that dont know the layout of the Snetterton circuit is below.... © 2003

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