[scott596]

Hi Mike, it sounds like your problem will either be if you`re lucky just the head gasket, or the head gasket could have gone because the head face has corroded away and is not clamping down on the gasket as it should, or as I generally find the combustion chamber starts to perforate as it corrodes within the water jacket and resembles the surface of the moon, the problem nowadays is finding a good secondhand head, I do a repair by boring out the old combustion chambers and making new inserts that are pressed in. You can also obtain a new head from Roger Moss. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

The Scott foundry were still looking for that part of the crankcase pattern years later.

[scott596]

Hi James, your picture of the 1947 Scott shows Dowty forks uninflated it also shows that the front brake backplates have been reversed to slightly improve the braking effect, all brakes should have their levers pointing forwards! here is a picture of my Brum fork yoke from 1964. Alan Noakes scottworkshop@hotmail.co.uk

[scott596]

Hi James, this part of the lower fork yoke is not normally drilled and tapped and serves no function the loose split sleeves that sit in this part of the yoke would have been zinc plated originally and are clamped up with the fork tubes by the bolts on the inner side of the fork tubes, by the way these Brum forks are not Dowty`s they just look like them. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi Martin, if you intend to fit long stroke barrels with 6X inlet ports to your short stroke crankcase you will need to bore out the crankcase through the crankcase doors and around the main bearing cup in order to fit long stroke cranks you will also have to use long stroke con rods, the transfer ports covers will fit either stroke. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi Kev, you could try using a 1″ sanding drum to change the radius on the switch and maybe the clamps would still work with a bigger gap between the ends. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Just finished Richards head, have fitted standard shape combustion chamber inserts to original Silk casting. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

James I forgot to say if the lever is on centre when the brake is applied then the cable will be the furthest away it can possibly get also the cable line will be the same at 10 degrees before centre as it is at 10 degrees after centre. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi James, you will have to experiment to get the correct brake lever position it is not just moving the lever round one notch, you might try turning the lever over IE inside to outside or swapping the right lever for the left lever or even taking the brakeplate off and turning the cam round 180 degrees, the lever splines were not broached accurately about the centreline. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi James, may I comment on the Brum front wheel photographed, as you have probably gathered there is no rigid originality that applies to all Brum Scotts, what they came with depends on who built them in the first place, there were three ways to buy a new Brum Scott, from the factory, from Geoff Milnes in Leeds, or from Ted Murphy in Sutton, when I ordered my Brum Scott from Ted Murphy I had to wait a few months while he built up other peoples machines and I can assure people that he collected seperate items from Matt Holder and built the bike from scratch, as I often called round to his premises and watched the bikes take shape and some minor things like wheel rims etc. would have been carried out by a local wheelbuilder.
Getting back to your photograph, the fork casting at the bottom is nearly always painted black, the inner brake cables are far too short and the brake levers are already over centre before the brake is applied, as I said not all Brums had painted wheel rims the one shown is spoilt by over thick pinstripes painted in the wrong colour red and looks terrible. The correct colour red for painted as opposed to laquered Scott cylinder barrels, vintage tank lines, and wheel lines is MIDLAND RAILWAY RED this is easily obtained from Craftmaster paints who advertise their products on E_BAY. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi Richard, when I restore detachable heads my inserts are made to exactly mirror the contour of an original Birmingham cylinder head that I have in my posession these are slightly more conical than a Shipley head but not much, and will bring a standard Scott engine back to it`s original compression ratio,obviously if an engine is bored oversize or has Silk pistons fitted this will also increase the compression ratio. Another point that concerns your particular engine is the fact that if you have Silk cranks fitted they are a slightly longer stroke at 72mm. compared to the 71.4mm of a Scott longstroke crank, this will lift the piston an extra .012″ into the combustion chamber and will also slightly increase the compression ratio, so a carefull check on piston to head clearances will be required. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi all this post seems to have gone off at a tangent Richard Rawson asked a question that still has not been answered yet, why does his Silk head which is shaped internally and should be of higher compression, hold so much more liquid than a standard type head? and regardless of actual compression ratios the Silk head will always be of lower compression than a standard head when fitted to his engine.I will also have to correct Richard Moss as my picture is of a similar Silk head made and marketed during the 1970s and probably from the same batch as Richard Rawson`s, and although it might look outwardly similar to a Moss high compression head this one has never seen the inside of Rogers workshop, the Silk head in the picture was bought secondhand by me in the 1980s from John Farrar he had probably bought it new from Silk engineering. I knew George Silk when he moved to Darley Abbey and at that time George had many irons in the fire, lots of different components needed to be made, new staff taken on etc. and George could not oversee everything that was going on, obviously these heads escaped the inspection department, I have just taken the time to measure the head in the photo and have come to the conclusion that the pattern that was used to cast the combustion chambers was incorrectly dimensioned and no amount of machining will ever improve matters they are just too big. These are dimensions that I have taken from parts that I have in my workshop, Diameter of piston crown taken from random pistons including Silk =2.837″ Approximate diameter of standard Brum and Shipley combustion chambers =2.875″ giving .019″ clearance around piston if chambers are centralised on bores, the shaped chambers on the Silk head are not only much deeper than a standard head but the diameter measures 3.010″ giving a clearance of .086″ all around the piston and I must emphasize that the chambers are as cast and have not been machined in any way. So I have to say to Richard Rawson you do indeed have a very low compression head and your Scott engined Silk would benefit from improvements in this department.
Richard Moss asks if I have ever made any close fitting combustion chambers ? the answer is a long story for another time but the Farrar Noakes racing Silk that he has pictured on his website has them installed. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

I hope this photo shows the type of head being talked about, the problem with this design is that there is always too much clearance down the side of the piston crown making the flame path just as long as a standard head so just because it is shaped like the top of the piston it is never going to be a proper squish head. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi Rob I charge £50 for doing the work plus the current cost of a new sprocket blank, the last one I bought was £28, plus the postal charge. Alan Noakes. scottworkshop@hotmail.co.uk

[scott596]

Hi Rob I can retooth your existing sprocket if you are interested. Alan Noakes. scottworkshop@hotmail.co.uk

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