I have been following this interesting thread for a few days now and have noticed that the use of Chrome piston rings is suggested.
A word of warning is needed here, Chrome piston rings should not be used in a Chrome cylinder liner, Chrome rings should be used in a cast liner. If in doubt check with who ever you source your parts from they should be able to sort out the correct parts.
Re Cord rings yes remember them well they used to be readilly available and I used them to keep our old Austin A40 going for many years before it was treated to a rebore then it went from standard size to plus 60 thou oversize in one leap! I believe Cords (or rings of similar design) are fitted as original equipment in some engines to this day.
As well as checking the items mentioned check very carefully the very fine mesh strainer that is pushed into a recess oposite to the metering valve. This can become blocked yet still appear to be clean and you may need to hold up to a light and veiw it through a magnifying glass to see the blockage.
Re information try the web sites for Walbro carbs and Zama carbs they have excellent technical help sections.
Almost certainly the breather valve has come adrift from the underside of the filler cap. The valve is normally held in place by the moulding and spring clip that also secures the fuel cap restraint line that in turn hooks into the fuel tank to prevent the cap from getting lost.
New caps are still available if you search the internet you will not be disapointed.
From your video it sounds as though you are getting there but your theory about the throttle butterfly actually works opposite to your thinking.
When the engine is at rest the light spring to the air vane will pull the throttle open allowing the engine to fire up but as soon as the engine is running air from the vanes on the flywheel blows against the airvane to close the throttle, engine speed is then controlled by tensioning the light spring connecting the vane to the throttle lever where the cable is attached. As the engine slows down when loaded air speed from the flywheel drops allowing the tension spring to to open the throttle further until speed picks up again allowing the engine to cope with changes of load when working. For this reason the spring over the cable is rather important, you could try a spring from a biro as an experiment but something a little stronger would be ideal, unfortunately the spring that you have fitted is not needed and should be removed.
Hope this help you to understand how the governor works if I have missed anything I am sure wristpin will fill in the gaps for us.
I have a 2.5 litre cleaner as the attached link and I have found that it is just the right size for occasional use on most small engine carbs without incurring the expense of a larger perhaps more commercial machine, you would certainly struggle with a smaller capacity tank size. And a heated tank is a useful bonus.
Interesting point about the effects of U/S ceaning on bearings I had heard the tale of vehicle wheel bearings suffering from Brinnelling during rail transport but not heard of this effect before.
Re the leak down tester it certainly means you have gathered your tools wisely.
I must have lead a sheltered life as I have yet to see one in the flesh either in or out of a "professional" workshop.
Just out of interest what sort of pressure needs to be applied? I have a Mity Vac tester kit that I use to test two strokes for vacuum leakage that is also able to provide positive pressure and it would seem fairly simple to make an adaptor for the plug hole.
Yes Mag Base Drill and Roto Broach type drills are very good but as you say the MagDrill is the expensive bit. I have not been involved in the hire of tools for a few years now but I do remember that some tool hire companies used to have them available.
Yes definitely can be cut using a decent brand of holesaw, try to use a drill with a slow to medium speed and plenty of cutting fluid (WD40 would do). The brand that we used to get for such jobs was Starrett and the largest hole that we cut was 4 inches diameter through 2 inch plate.
That is quite some collection of saws you have there,
I recognise in the foreground of picture four a Danarm / Consolidated Pnuematic air saw, have you had this saw running on air? The pair that we had at work were powerful beasts but fell foul of elf and safety regs with no chain brakes etc so ended up in a local saw collection along with their hand books, spare parts also became a problem if I remember correctly.
The claim was that these saws could be safely used under water but I never saw that put to the test!
I have been watching your progress with this project and you are doing a superb job on what was in effect a basket case mower.
Re regrooving the tyres I am not sure how they will react to being machined as rubber can be notriously difficult to deal with, If you have little joy producing a good result then talk nicely to a local commercial tyre comany and ask if they can regroove them for you using a tyre regrooving gun, they cut the rubber using a heated blade and produce a good finish to the cut area.
Looks as though you have been busy, re the cut down springs perhaps they were cut down to eke out a bit more life from a worn cylinder then it was changed later without replacing the springs. From the photo it seems as though this cylinder plenty of meat left on it.
When you separated the roller sections did you find wear in the inner bearing of the roller section that still had half of its grooves unworn? If not it is a bit odd that the roller has worn in the way that it has.
If the original cap fits ok and does not leak I would leave well alone as trying to dismantle it may well create worse problems and you end up with no cap! Just look upon the dents as Patina.
I must have chased one of those machines for a good few miles up and down the rows of Runner Beans on the market garden that I used to work for in the school holidays - that was a good few years ago now,
That is a lot of header to try to watch what is being swept up into the drum - things like lumps of concrete, old bike frames etc used to be the cause of damage to elevator cross bars, drum rasp bars and concaves on machines working near housing estates.
Another quirk of the Massey 780 & 788 range was the strip of canvas used to cover the access to the concave located just under the threshing drum and accessed by climbing under the raised header and reaching up over the batteries and the engine. This was very popular with mice and was always eaten at the lower corners! It was held in place by a row of 7/16" AF nuts and bolts along its top edge and long pin running through an eye sewn along the bottom edge of the canvas and always seemed to be the apprentices job to fit the new ones - such fun.
I am inclined to think they are not the same machine to much distance in between locations, I don't think that UK farmers are into the custom harvesting operation like they are in USA. Those guys cover immense mileages between farms never mind around there fields.
I think that the combines shown in wristpins photo are the Massey model 780 with the air intake to the radiator vertical, the later 788 had the horizontal intake. The machine nearest the camera is not one that I am familiar with I would guess it is a Viking by the name on the grain tank but don't know who sold those around this area.
Happy New Year
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Happy and safe new year to all from Dover.