After 32 years of rebuilding my flyer , finally got to the point of starting the engine today. Result nothing, not even a pop or puff of smoke 🙁 .
Checked timing – OK, Blue spark on both plugs, Fuel and Jets seem OK. WD 40 down intake – still nothing
I was wondering about the induction stroke , is it possible to check the crankcase pressure and whether it draws a vacuum, its just that if I put my hand over the air intake I can’t detect any noticeable change in pressure. The top end is good having new rings fitted. It was a big disappointment today as I’ve never had it running , probably not been fired up for fifty years 🙁
You could try swaping the leads over that mistake has been made ( in the words of that famous police chief ) many many times. . regards D F.
A good and simple check for crankcase suction is as follows:- Petrol turned OFF, plug leads taped metal-to-metal onto crankcase to earth them, spark plugs removed, put into top gear, back wheel off the floor, throttle wide open, air lever wide open, then by hand turn the back wheel smartly forwards. If all is well you should hear a distinct ‘plop’ noise, twice per engine revolution, rather like the sound of a cork being pulled from a bottle.
I hope that you are successful ! If not, there are several possible culprits, and first of all check that any crankcase drain plugs are in place ! (Easily overlooked in a rebuild). The next possibility is that the engine has been assembled without cylinder base rings, but removal or lifting partially of the cylinders is needed to check that item.
I presume that you are following the correct cold start procedure ? Oil tap on, petrol on, flood carburettor generously (if Amal type), until fuel pees out of the float chamber vent hole and drips onto the flywheel. With throttle and air lever closed kick engine over a couple of times in order to draw some mixture into the crankcase. Then open throttle about one third, and give the proverbial ‘long swinging kick’ on the kickstart. If it doesn’t show any life at all, try switching the plug leads over. Usually if the leads are on the wrong side, you will get some pops and bangs in the exhaust, and nothing at all is not a good omen…..
Finally, well firstly really, make sure that your petrol is absolutely fresh, as this modern stuff containing ethanol, benzene, etc., has a ‘shelf-life’ of only about three weeks in your tank before it loses its low-boiling aromatics that are vital for easy starting.
Good luck !!
For a two stroke engine to work properly it has to be an efficient pump, and to achieve this the internal parts have to be sealed from the atmosphere this is achieved by coating them in oil, if your engine was assembled more than 3 or 4 months ago the chances are that the oil used in assembly has evaporated, we are talking mainly about piston sealing and glands, both can be rectified by liberal use of an oil can and won`t require removing the engine probably just oil pipes from crankcase unions, transfer covers and mabe the carburettor, when everything is OK you should hear a distinctive plop plop plop as you kick it over, good luck. Alan Noakes.
Thanks Brian scott56 and Dripfeed,
One question, should it be fully advanced when starting ?
Quite a list of family/household commitments today which is why its taken 32 years to-date 😳 If I’ve a spare hour today , I’ll give those suggestions a try and report back.
Best wishes Jonathan
Yup, full advance.
On about four occasions I have had difficulty in starting Scotts with rebuilt engines or that have been standing for a long time. It seems to be a lack of suction in the crankcase caused by the glands not sealing adequately. I have managed to get them started by a push start as the increased speed of turning over the engine negates the leakage past the seals.
On one occasion I had to resort to a long bump start down a 1/2 mile hill with the engine popping and banging until the engine would run consistently. 15 minutes later after riding it around and back up the hill it started just the way it should. After a bit of regular use the bike would start from cold on 4th or 5th kick. This was my TT Rep I had not used for about 6 years.
My 2 Speeder, after its rebuild, also needed a good push around the garden before it started for the first time. This bike seems to like full advance when starting from cold, possibly due to the spark being a little weak on retard or a cold mixture being reluctant to fire. When warm it will start first kick and must have the ignition retarded otherwise it will kick back.
Well I’ve reseated the barrel end gaskets, tried again, NOTHING !!!!!
5 Hours later , with kick start leg fatigued decided to read Glyn Chambers description of setting the points. Guess what I’ve been doing ,
………….setting them as there are closing and NOT opening. 😳
1 HOUR later , dinners about to burn !!!, Kick over with plenty of WD40 ……. NOTHING
Swapped leads over……………………….IT FIRED 1st Time ( ist time in about 50 years) 😆 😆 😆 😆 😆 😆 😆 😆 😆 😆 yipeeeeeeeeeeeee
Just need to sort the carb out now, its a three jet binks, seems the float level is to high or the float is not doing its job, I can see fuel leaking out the lower of the jets.
Do I need to replace the needle ? can the level be adjusted ?
Thanks to you all an exhausted but happy Scott owner
At last !! You must be very pleased Jonathan…. Now is your Binks Three-Jet the earlier type with an integral bellmouth, and big hexagonal top nut ? Or is it the later type with separate bellmouth and knurled top ring like an Amal ?
Yes its such a good feeling , after so long , its a massive milestone. This forum is such a valuable resource, thank you.
Its the later type, with a screw in bell mouth. I’ve looked at various models but can’t see mine. Its very simple , three jets , one flush. air slide and throttle slide.
No slide stops or float stops. Just a nut below the float chamber and a nut at the fuel inlet union. Not sure how to adjust the float level ?, maybe its upside down ?
Personally, I don’t like the Three-Jet Binks, but I’ve had lots through my oily hands over the years, and have lots of bits for them. The entire float chamber assembly on the later ones is exactly the same as on the Scott-Amal carb, so parts for the float chamber are readily available ‘off the peg’. The petrol level with the bike standing on level ground, and not on the stand, should be JUST below the top of the first, flush, jet, so that mixture is readily sucked out of it at kickstart engine speed by the proverbial venturi effect. It sounds as if yours is fractionally too high, so your float needs tweaking downwards with a washer or two on top of the float where it sits on the step in the float needle. While you are at it do check that the taper on top of the needle is in perfect condition. If there is any sign of a wear ridge do renew the needle.
Onwards and upwards !!
Yep, the taper does not look that good, so I’ll source another needle. Are they just standard washers to set the level lower ?
Some stainless steel washers would be best, as anything else is likely to corrode due to the ruddy ethanol in petrol.
I think I’ve got some small ss washers, probably got some brass BA washers as well . So just keep adding until level just below lowest jet.
Incidentally the crankcases are holding a bit of petrol in the bottom , is it OK to start it with this in ?
So long as it is very oily petrol it should be OK.