Hi all, my first post and a few questions.
i have bought a ’59 Birmingham Scott and am having trouble getting it started.
I’ve re-wired it and have a good correctly timed spark.
clean carb and lots of fuel(using 40:1 mix). There seems to be a lack of crancase suction /compression. The bike will only start if i remove the transfer port covers, oil the pistons , re-assemble with clean plugs and off it goes 2nd kick. of course the garage fills with smoke hence the gas mask ; but it is at least it is running.
Once warmed up i stop the engine and it wont start again until i repeat the process. If i don’t there is a distinct lack of suck through the carb.
There is plenty of cylinder compression and although the bores are a little worn I would have thought the pistons would be tight enough to force the mixture through the transfer ports.
The other worrying thing is that the oil is not being taken from the pilgrim Pump sight glasses to the c/case. hence the use of 2 stroke fuel.
My questions are:-
1 Does the Pilgrim Pump force the oil into the c/case or is it just sucked in?
1a my pump overflows at high drip rate.
2 The handbook says “Fill the oil wells in the c/case” where are they and what is the best way to fill them?( i have put an egg cup of oil through the transfer ports )
2a Are the 2 plugs under the engine just to drain the c/cases or are they drains for the aforementioned oil wells?
3 The engine had been rebuilt but not run before I bought the bike , is it possible there are leaks between the cylinder base and inlet system messing up the inlet process?
Otherwise it is a nice machine and has had a lot of money spent on it (paint wheels polishing exhaust all new. ) and it has a 4 speed velocette gearbox, supposibly factory fitted.
ps the off side toolbox is the oil tank !
Thanks a lot Mick (my first 2 stroke for 40 years )
Q1. No, the oil is basically metered by the pilgrim although it does have some pumping action. The oil is sucked in by crankcase depression.
Q1a. The oil should be adjusted so that it drips into the pump once for about 4 pulsations at the beak, visible through the pump window. Also check that the correct rotation pump has been fitted when the engine was rebuilt. An arrow indicates direction of rotation and is on the face of the pump where it attaches to the distributor housing.
Q2. The oil wells are at the bottom of each crankcase. Normally there would be no need to fill them unless the engine has just been built up, and then do it through the crankcase doors before you put them on. They fill up naturally and provide just a little reserve should you empty your oil tank, but don’t rely on them to keep you going for long! They also lubricate the big ends, which dip into them when you first start up.
Q2a. They drain the oil wells and crankcase (same thing!)
Q3. There are many reasons for difficult starting, most are due to air leaks. Check crankcase door gaskets, transfer port gaskets, cylinder base gaskets, carburetta seating and crankcase glands. The latter could be the reason the oil is not leaving the pilgrim pump. The glands are handed and ported and if they have swopped sides during the rebuild, they won’t be opening at crankcase depression.
The Velo gearbox was a mod that appeared in Yowl in the sixties.
1: The pump only meters the oil, the engine have to suck it, itself.
1a: Adjusting the pump is next to impossible, somewhere one click above
2: See the drawings somewhere in this world of knowledge
2a: Don’t know
I think the missing engine sucktion is the problem, check for leaks somewhere in the crankcase, – packings in the crankcase doors etc. packing glants
From the symptoms described, I would suspect the piston rings. If they are stuck, you will not build up sufficient pressure or vacuum in the crankcase halves. My suspicion is built on the fact that you can start it if you oil the pistons as described. I suggest that you take off the cylinder block and check the pistons. It is easier than taking the engine out – as a first step. There are almost always problems with a Scott engine which has not been serviced properly through the years. Disregard its history which you have been told and check for yourself. As a rule, money has been spent on nice looks, not on a proper restoration of the engine and gearbox.
Please don’t continue to run the engine relying on petroil because the main bearings and sealing glands are not getting any oil and you will soon do some damage. From your description of its behaviour I would also suspect stuck or broken piston rings, closely followed by missing cylinder base rings and/or wrongly fitted glands. You do not need to remove the cylinder head from the barrel to sort out your problems. I recently came across a Scott where the rebuilder had wrongly connected up the pipes to the oil pump! Do check that the supply pipe to the pump goes to the correct orifice on the pump body. This is usually the one at front/right, but there are some oddball pumps around with different internal drillings, and the feed connection elsewhere. Another thing to check is that the union that screws into the oilfeed hole on the pump is not too long and obstructing the internal drillway. I have recently rebuilt a batch of pumps and found all sorts of other rebuilder’s cock-ups such as plungers swapped into the wrong side, blobs of gasket goo blocking drillings, etc.. To check that you have the correct rotation of pump, you look at the drive end, and there should be an anticlockwise arrow engraved or stamped on the body. Pumps on the left-hand side of a Scott, such as 1939 Clubman Specials and some Sprint Specials, are opposite handed and not interchangeable. Internal parts are also not interchangeable.
Hope this helps.
thanks for the advice and answers.
The fill the crankcase with parrafin checked the seals,
there ok thank goodness,
I got the barrels off this morning and the rings where stuck and a bit worn.
The main trouble was the square section rubber rings at the bottom of the barrels had not seated properly one was cut and the other side damaged on the other. (suspect they were old stock and had swollen)
so its new piston rings (+0.060″ if i can find them ) and ‘0’ ring seals from Ireland.
I’ve not run the bike too much so no damage done.