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After getting the engine to run found it had quite bad piston slap, however much looks unworn, after getting the mag to work better so easier to start found it run perfectly for thirty seconds but then started to 8 stroke and longer it idled the worse it got and if stopped lost what little compression it had, and would often flood after stopping, spent ages with magnifier trying to see any damage to the needles seat, made a dummy needle to lap the seat, putting the needle back in, fitted the fuel line back on and just hold the carb upside down without the weight of the float not a hint of a leak past. Assembled and run perfectly then back to 8 stroking, looking at the way it works its a rather lacking in design as the float just twists over so restricts free movement this has worn the centre hole through the float. I had an idea as its a bit like standing on one side of a dingy so there is no reason why supporting the opposite side wouldn’t work and improve pressure on the needle, there was already one set screw that hols the copper gasket and adding another wouldn’t cause a problem. Its not running perfect at least theres no black smoke and it doesn’t flood, must spent a day just on the carb making clamp set screw, slide top ring nut and the float mod. Going by the dented float they had resorted hitting the float tickler and with it having the parting off spike left on had dented the float in many places both sides. By the way anyone know the make of engine as it needs a piston, and what year of manufacture.
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Never knew the bicycle three speed makers made engines. And yes the float isn’t good but the worst bits are inboard of the float needle, the tickler goes through at an angle. I was hoping they used a engine from a well known motorcycle manufacturer. so might have found a piston, not a problem making one but then would have to balance the crank as wouldn’t use the heavy cast iron. To start with you have to calculate is it a two or four stroke, as can start as little as 50% for a two stroke and as much as 70% for a four stroke, then its add the stroke, revs, is it a horizontal or vertical and with the weight of frame its to be fitted into as that can cause harmonics to set in.
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Andy
Yes many pistons were changed without balancing and often they got it wrong to start with and comes down to a good bit of guessing and if you get it right its so satisfying. I restored a 1905 Rover 780cc 6HP single cylinder car engine the balance was was a bit lucky with a new rod of different design and lighter piston, however taking masses of weight of the reciprocating mass is like loosing quite a chunk off the flywheel weight so effects idle.
Well think they said normal running 24mph was 900rpm but could be run be run up to 1200rpm that gave 28mph and returned 40 mpg, Well with a bit of experiment with the induction length we could better 40mph and got 70mpg but at a cost of low down torque and getting it nice to drive knocked it back to its original 28 max with still 50+ mpg in all conditions.
I also found a bit of interesting or what was used early on was Masked ignition where the plug sits in its own combustion chamber, and it works, a engine can use vast quantities of oil and not fowl its plug, and if taken to extremes will only run a engine at well below -20 degree and above will overheat. My 1905 Rover wasn’t fitted with the Masked plug chamber later on it just appeared, A mr Alfred Feaviour got commendation on improvements to early aircraft engines and later sold as plug savers which I have one this was also used in cylinder heads from small equipment to car engines. I was asked to a old tractor that its mag wasn’t good and noticed it back plug sat up not on one of the plug savers but three so don’t think that cylinder would have been doing much. photo of a very lighten rod by rust and the un-masked 05 plug with the later 06? later, so Rover, emergency aircraft generator and one of the plug savers.Attachments:
Andy
I used to use Knights engineers in Norwich, I can remember John Knights saying leave it with me and will try and find something and he did, I believe he was looking through old Hepolite books, maybe one of those old books would be a start.I used to use JP pistons Australia with some still in use today without issues and were very reasonable in price, I then had the odd problems with wrong pistons but same part number and loose pins. So I then went west to Arias pistons that were high quality
forged alloy and with some old engines being long stroked and small bores so little oil got to where needed, could specify the old type of non aggressive cast rings and pin fit, even making only 6 pistons of 4”inch bore came out little over £120 each when the cast JP small Triumph motorcycle were £80 so got some surprises. Photo of what know it all people do, the deep section compression rings intended for diesel engines with egressive oil control made the engine so tight they added 12volts to the huge 6 volt starter that then climbed up on the ring teeth to tear the bearer out of the alloy crankcase. The replacements I had made with fraction of the cast iron weight reduces so much of the stresses.Attachments:
Grahame
Think I am going to try and find a small motorcycle carb, the design of how the float tries to shut the fuel off just doesn’t, I must have spent 4hrs carefully taking apart removing dents, cleaning and back together. I had just fitted it and was interrupted for an hour, came back and hurrah still dry, started and within less than a minute was flooded. So the before, I couldn’t get the worst marks out but the just distorted side came out perfect. if people don’t know when going to solder a float always find the blow hole and drill it before heating, after repair cool and then touch in the blow hole.Attachments:
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