The exploding Scott -update, and a few questions please

[eyeguy]

Hi chaps
I’ve removed the engine, and have made plans to take it up to Roger Moss next week ,he will strip it with me and we shall decide on a plan of attack. It will need new cranks(obviously) and I hope to hop up the motor with a little porting perhaps, and try to fit a non leaky carb. Whilst originality is nice, a burnt out original bike has little appeal!
Some questions please:
Has anyone tried a ‘modern’ carb(eg Amal Concentric)?, and does that reduce leaks?
Should I have the flywheel scribed to make timing easier?
Anything else I should consider, such as Electronic magneto?

I’ve also removed the undertray for inspection and possible slotting, and whilst it’s all out put the gearbox on the bench. On removing the large alloy cap I noticed that the box is filled with what looks like grease, not oil. There is a chance that the old oil has mutated into gel lumpy stuff lubricant, but it looks like grease, with loads of it stuck uder the cap and around the neck.

What’s the expert’s opine on what I’ve found, and do I need to get rid of it, if so, how, and what goes in it’s place?

With thanks

A tutto gas

Paul

[chstorm]

Hi Paul,

As Eric said – one gets a feeling of deja-vu!

There is no reason why a healthy Scott/Amal carburettor should leak.
There may be three reasons:

A leaky or too heavy float
A worn float needle and seat
wrong positioning of float chamber (should be level)
– or a combination of all three

All three will lead to a petrol level which is too high, and petrol will leak out of the main jet in the carburettor body.

May I suggest that you, while the engine is worked on by Roger, send the carburettor away for overhaul. I will recommend the service of:

Martyn & Tracy Bratby
No.1 The Coachouse Works
Limepit Lane, Huntington Cannock,
Staffordshire WS12 4PA
Telephone: 01543 572583
Fax: 0777 2169524

Martyn has restored several carburettors for me, has all the parts, and does an excellent job. His wife Tracy, by the way, bakes very tasty biscuits.

I am sure that Roger will give you excellent advice about what to do with your engine. He has successfully rebuilt two Scott engines for me, and both go like bombs, with little vibration – a lot of torque and admirable acceleration. Ask him what he did to my engines – I would recommend the process!

New high-tensile cranks
No change of porting, but:
full gas flowing of engine with ported Silk pistons
High-compression heads
Added weight to flywheel
“scribed” flywheel for ease of timing.
Size 200 main jet in carburettor

I have kept the original Lucas Magdynos (overhauled though). The new BTH electronic magneto and generator is exellent, I use that magneto on my Vincent Black Shadow, but there it can be hidden, which is not possible on a Scott. The BTH unit will look OK on the bike for those who do not know. It has the added advantage of an automatic advance/retard mechanism and large amount of 12V current for night driving. Expensive though.

Further, I would advice you to bring engine and undertray and gearbox to Roger for inspection.

As to gearbox lubrication – this is what I answered another guy some time ago who complained about a leaky gearbox (I suspect that grease may have been used to stop an oil leak):

“First a (maybe silly) question: Have you filled oil up to the correct level? There is a hexagon screw in the front end of the r.h. side of the gearbox, -an oil level plug. Before filling with oil, you unscrew this plug. If oil is running out, you have filled too much. Else refill until oil comes out of the hole, and let it run until no more is coming out. Then refit the plug. I had an oil leak from the gearbox on my ’36 flyer, and discovered that the oil level was too high. With the correct level – no more leak! You also need to use a sufficiently heavy oil. A SAE140 straight (no hypoïd) gear oil (Shell Dentax) is OK. It has a “body” similar to a SAE 50 monograde engine oil. If the oil is too thin, it will splash about a lot more than a heavy oil. Personally I use Castrol R40, which may sound a bit exotic, but it adheres beautifully to all internal surfaces in the gearbox.

If this does not help, it is possible to fit a modern oil seal. I have had that done on my ’38 flyer in connection with a recent gearbox and clutch overhaul. I am certain that Roger Moss, who helped me, can steer you in the right direction.”

Best of luck! We have all been through this stage of “Life with a Scott” – You have my sympathy, but on the other side, you will have a lot of fun!

Kind regards,

Carl

[efr215]

On the subject of leaky carburettors have a look at the postings dated Friday March 10th 2006 and Saturday April 14th 2007 where the matter was examined in some detail. With the fuel “on”, other than when “tickled”, the Amal should not leak even when the engine is not running, if it does then for one reason or another the fuel level is too high or one or more of the soft gaskets are defective.

I cannot offer any help regarding settings for alternative carburettors but there is no reason to suppose that any unit with the correct choke size could not be made to work once the correct settings are arrived at. Getting the settings is quite another matter; you really need a test bed to do it properly . . .

On the subject of the grease in the gearbox: It may be that the main bearing has been leaking and a previous owner has used grease in an attempt to stop it. There are also thixotropic lubricants about these days so it is just possible, however unlikely, that it might be one of them. The Burman gearboxes on the Vincent Comets use grease, (with the caveat that if it starts to squeak you add an eggcup full of oil!), so while it is customary to use oil in the Scott gearbox the use of grease is not quite so off the wall as it might at first seem.
It is most unlikely that there has been any “mutations”. Quatermas we can do without – I’ve got enough problems!

Timing marks are a good addition to my mind and can certainly do no harm. In addition if you have a strobe light then checking timing is made easy by their addition particularly if filled with white paint. You can always ignore them if you want but you can’t use ‘em if they ‘aint there!

There is nothing wrong with electronic ignition in principal although to get the best out of such a unit it should really be mapped to the engine but for that you’d again need a test bed. That said a properly set up conventional ignition system, either coil or magneto, has served bikers well for donkeys years and an awful lot of miles!

[eyeguy]

Thanks Guys, that’s just the sort of advice I needed. I’ve still got my doubts about a dodgy old 206 fitted at a 30 degree angle, though. I’ve cleaned out the gearbox, it was grease, and I’m taking it up to Roger with me, as advised!

I’ll let you know what the maestro says.

New offer just in for the Scotton, while there’s hope…

ATG

Paul

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