Ransomes engine carb improvement

[davidbliss]

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.

• This topic was modified 21 hours, 5 minutes ago by davidbliss.

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[andyfrost]

Dents in your float will make significant issues on running , engine appears to be Sturmey Archer.

Andy.

[davidbliss]

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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[andyfrost]

Ransomes used Sturmey engines quite alot , the MG2 crawlers for example.Piston material…..well I think you’re trying to get too technical , remember many engines we play about with originally had cast iron pistons , but replacements such as hepolite etc. etc. went over to alloy , with no modification to any components. Just one of many examples is the Villiers 25C , originally cast iron , but replacements available in alloy with none of the issues you mention.

Andy.

[charlie]

It might be worth contacting Cox and Turner Engineering aboput a replacement piston.

[davidbliss]

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.

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[sidevalve5]

Dear David,

Fantastic descriptions and pictures of your precision engineering skills. You remind me of an old boy who does a few little jobs for me. He has made scale stationary, steam and aircraft engines from scratch. What he can do amazes me and he is in his eighties.

Without those abilities people like me have to try to work with what we can obtain. I had the problem of getting hold of some piston rings for a Gravely D. No chance as named spares, but whilst researching fell upon Hastings Piston Rings. After reading their very helpful technical guidance, found a set that fitted in their brochure. Although they were an American company, they had a franchised distributor in the UK. So ordered them. They could have also supplied some for a Jap 5, but in the end as Cox & Turner had them in stock. Purchased some from them.

Was told once Ford Consul pistons would fit a Jap 5. This was not true, but after the success with the rings I tried to do the same with specialist piston suppliers. Was hoping to find a way of getting a replacement piston when it was not obtainable as a named spare part any more. But have drawn a blank. I cannot find on the internet a catalogue where I can cross reference: bore, gudgeon pin diameter, compression height and crown profile. Does anyone know of a method of doing this. Where it may help David, or anyone else, is to obtain nominally obsolete pistons to keep their old engines running in good order.

My elderly engineering friend has a large and rare oil engine with the plug, or more like a pair of electrodes, sitting in a chamber outside the cylinder. It’s a lot cruder than the Rover one shown in your pictures. As for the carb, I would just fit a modern one if parts are no longer available. As I think some of the older types were just too rudimentary and unless in good condition, cause a lot of problems. But I am more interested in performance than originality. Others may take a different view and can well understand that.

Best wishes,

Grahame

[andyfrost]

Grahame , interesting post , out of all the countless engines that have been built over the years , rings from some engines will fit others , it would be interesting to pool all our knowleddge onto a permanent topic on this site , one example that I stumbled across a few years back , Anzani Super Single outboard are the same as Shay120cc. Another from years back , Hillman Imp big end Shells will fit the single Cylinder Scammell fire pump engines. I suspect we would all be very surprised what crossing of rings could be achieved if only we knew , obviously with pistons , it’s far more limited.

Andy.

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