non starting Birmingham scott

[Roy Charlton]

Hi Scott owners,, I have been following the saga of the 1958 Birmingham Scott with avid interest. glad to hear it got started.
I am having a problem with starting my 1957 B-ham Scott after a engine rebuild i e fitting new rings and gaskets etc I have owned the bike for thirty years it was last taxed in 1973 and has been garaged until four years ago when i started to dismantle it and then do a total rebuild
the only way it will fire is by pouring a small amount of fuel in the plug hole it starts it fires up then stops does not appear to be drawing fuel through the rebuilt carburetor help Roy

[BRIAN MARSHALL]

Take the spark plugs out, turn fuel off, ignition off, open air lever (choke), open throttle fully, and then gently operate the kickstart. You should be able to feel crankcase compression, and hear a plopping noise, like the cork being pulled from a bottle, twice per revolution of the flywheel. If the crankcase compression is ‘missing’, then the engine may have been assembled without cylinder base rings, and it will not be able to draw in any petrol/air mixture. With the plugs back in, and your hand over the carburettor bellmouth, you should be able to feel strong suction as the engine is turned over. If you are not a contortionist, and struggle with that, do it by putting the bike in second gear, and then turn the engine over by turning the back wheel by hand.
Let us know the outcome of these checks, as there are of course other possibilities, such as a blocked primary airway in the carburettor, wrong ignition timing, etc..
Brian

[Roy Charlton]

thank you Brian for that info did as you said, did not feel a great deal of compresion and heard more of a bumph noise than a plop but I do have a hearing problem, with plugs back in there is a very good commpresion and a good strong suction in the carburetor
what do you suggest doing now regards Roy

[BRIAN MARSHALL]

Check that the float needle is not stuck in the underside of the float chamber lid, and that the carb pees petrol out of the vent hole in the float chamber lid after you have pressed the tickler button down for a few seconds. Also GENTLY screw in the idle mixture screw to its limit, and then unscrew it one and a half turns. Then try starting it again with air lever closed and throttle approx. 1/4 open. Don’t forget to turn ignition on. Good luck !

[Roy Charlton]

Hi Brian, the needle was free and petrol peed from vents. also peed from small hole opposite side of mixture screw. no joy
i checked timing again piston nearest the distributor at tdc and points fully open,
poured a little fuel in to the bores it fired up once then nothing again. tried for several minuets and no joy, ?????

[dave bushell]

I take it that the pistons are in the correct way round after the rebuild?
Dave

[Ted Robinson]

I would check the carb main jet it seems there is no fuel from the carb to the engine. Ted.

[BRIAN MARSHALL]

The main jet plays little or no part in starting…

[Roy Charlton]

Thanks for suggestions yes pistons are correctly fitted …. a new main jet was fitted appears to be satisfactory, ????

[BRIAN MARSHALL]

Maybe the next step is to pull the carb apart and check that the very fine primary airway drillings in the jet block are clear. Some fuse wire is probably the best thing to poke through.

[Roy Charlton]

Hi Brian, striped the carb, i was not to impressed with the state of the bore etc so to eliminate the possibility that the carb might be source of the problem i am taking it to the auto cycle company in Dudley town on Friday they deal in amal carb’ spares and servicing etc they will strip and do whatever is required to get it as new condition. so on return if it cures the starting problem great if not then I think I will fit new cylinder base Viton o rings. unless you can think of something else to try….
Regads Roy

[BRIAN MARSHALL]

I’m sure that Chris Williams at Autocycle Engineering
will be able to sort out your carb, or if he is too busy Martyn Bratby also does a good job on them. While you are at it, the Viton cylinder base rings are also a good idea.
Brian

[Roy Charlton]

Hi Brian, Chris Williams looked at the carb said nothing wrong with it, so I removed the block oh dear one of the base rings was chewed in half so i am assuming this may be the problem, I will order new parts and hopefully this will cure the problem i will keep you informed regards Roy

[BRIAN MARSHALL]

I assume that you mean the hard fibre washer between the jet block and the big base nut ? If so, be very careful that the inside diameter is well clear of the suction hole in the base of the jet block. While you are at it, push some fuse wire through all the fine drillings in the jet block to make sure that they are clear, and blow through the main jet. With modern so-called petrol the main jet needs to be at least a 190 or 200.
You are not alone in your starting problem. A friend has just finished rebuilding his Scott racer from about 30 years ago. Good compression, good suction, good spark, timing checked and rechecked. Will it start ? Will it hell ! He is mystified, but is truly a Scott expert. Years ago you could walk into a chemist’s shop and buy little bottles of anaesthetic ether. I used to use it to make model diesel engine fuel. Add a bottle of that to a tank of petrol, and poor starters would become one kick bikes ! The Elf an Safety brigade have put a stop to that…

[Tman]

“BRIAN MARSHALL”]I assume that you mean the hard fibre washer between the jet block and the big base nut ?

I thought he was referring to the cylinder base ring?

The Elf an Safety brigade have put a stop to that…

“Elf and Safety” sounds a bit Daily Mail-ish, but NOT selling ether over the counter sounds like common sense to me. 😯

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